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Sample records for deposit western sichuan

  1. Development of foreland basins around western Sichuan basin, and implications for mountain building in eastern Tibet

    NASA Astrophysics Data System (ADS)

    Chen, S.; Liu, M.

    2014-12-01

    The Sichuan basin is surrounded by the Tibetan Plateau to the west, and the Michang Shan and Daba Shan mountains to the north and northwest. Foreland basins have been developed along the western and northern margins of the Sichuan basin since Triassic, receiving sediments with significant along-strike variations. These sediment records provide useful insights into the history of mountain building around the Sichuan Basin. We have collected exploration well data from western Sichuan Basin. Using backstripping, we reconstructed the basement deformation history, which reflect sedimentary and tectonic loadings related to mountain building. We used a 3-D numerical modeling technique with multi-grid technique to simulate flexural deformation of the Sichuan Basin lithosphere, and to infer tectonic loading and mountain building along western and northern margins of the Sichuan Basin from the late Triassic to the Cenozoic. Our results suggest that the shortening of the Daba Shan and Michuan Shan orogens mainly occurred during the late Jurassic-Cretaceous. During Cenozoic, the tectonic loading mainly occurred along the southwestern margins of the Sichuan Basin, corresponding to the development of the Longmen Shan mountain belt. The tectonic loading of the northern Longmen Shan on the Sichuan Basin has been markedly reduced since the Cenozoic, evidenced by the lack of Cenozoic foreland basin development. This indicates mechanical decoupling between uplift of the Tibetan Plateau and the Sichuan Basin, consistent with the deep down-cutting of the Longmen Shan fault and predominantly strike-slip motion on the fault. The limited Cenozoic foreland basin development in the southwestern margin of the Sichuan Basin is consistent with localized high-angle thrusting of the southern Longmen Shan mountains. This work was supported by the National Natural Science Foundation of China (grants 41104046).

  2. Lunar western limb pyroclastic deposits

    NASA Technical Reports Server (NTRS)

    Coombs, Cassandra R.; Hawke, B. Ray

    1991-01-01

    It has become increasingly evident that the lunar pyroclastic volcanism played an important role in the formation and resurfacing of many areas of the Moon. On-going analysis of lunar Orbiter and Apollo photographs continues to locate and identify pyroclastic deposits and suggests that they just may be more ubiquitous than once thought. Located near mare/highland boundaries, many of these deposits formed contemporaneously with effusive mare volcanism. The mantling deposits formed as products of fire-fountaining. Probable source vents for these deposits include irregular depressions at the head of associated sinuous rilles and/or along irregular fractures in the floors of ancient craters. Here, researchers provide a brief synopsis of the nature of the dark mantling deposits and briefly discuss several newly identified deposits on the western limb.

  3. Black carbon record of the wildfire history of western Sichuan Province in China over the last 12.8 ka

    NASA Astrophysics Data System (ADS)

    Sun, Weiwei; Zhang, Enlou; Shen, Ji; Chen, Rong; Liu, Enfeng

    2016-01-01

    Wildfire is recognized as a critical Earth system process which affects the global carbon cycle, atmospheric chemistry, and ecosystem dynamics. Estimating the potential impact of future climate change on the incidence of fire requires an understanding of the long-term interactions of fire, climate, vegetation, and human activity. Accordingly, we analyzed the black carbon content and the pollen stratigraphy of sediments spanning the past 12.8 ka from Lake Muge Co, an alpine lake in western Sichuan Province, in order to determine the main factors influencing regional fire regimes. The results demonstrate that wildfires occurred frequently and intensively during the late deglaciation and the early Holocene when the regional vegetation was dominated by deciduous forests. Wildfire occurrence decreased significantly during the Holocene climatic optimum between 9.2 and 5.6 cal ka BP. Overall, the wildfire history of western Sichuan Province is similar to that of the Chinese Loess Plateau and of East Asia as a whole, suggesting that regional-scale fires depended mainly on changes in the intensity of the Asian summer monsoon. In addition, the fire regime of western Sichuan Province may have been influenced by the establishment of human settlement and agriculture in western Sichuan Province and the southeastern Tibetan Plateau after about 5.5 cal ka BP, and by an intensification of cereal cultivation coupled with population expansion in southwestern China during the last two millennia.

  4. Genetic Structure of Qiangic Populations Residing in the Western Sichuan Corridor

    PubMed Central

    Wang, Chuan-Chao; Wang, Ling-Xiang; Shrestha, Rukesh; Zhang, Manfei; Huang, Xiu-Yuan; Hu, Kang; Jin, Li; Li, Hui

    2014-01-01

    The Qiangic languages in western Sichuan (WSC) are believed to be the oldest branch of the Sino-Tibetan linguistic family, and therefore, all Sino-Tibetan populations might have originated in WSC. However, very few genetic investigations have been done on Qiangic populations and no genetic evidences for the origin of Sino-Tibetan populations have been provided. By using the informative Y chromosome and mitochondrial DNA (mtDNA) markers, we analyzed the genetic structure of Qiangic populations. Our results revealed a predominantly Northern Asian-specific component in Qiangic populations, especially in maternal lineages. The Qiangic populations are an admixture of the northward migrations of East Asian initial settlers with Y chromosome haplogroup D (D1-M15 and the later originated D3a-P47) in the late Paleolithic age, and the southward Di-Qiang people with dominant haplogroup O3a2c1*-M134 and O3a2c1a-M117 in the Neolithic Age. PMID:25090432

  5. Genetic structure of Qiangic populations residing in the western Sichuan corridor.

    PubMed

    Wang, Chuan-Chao; Wang, Ling-Xiang; Shrestha, Rukesh; Zhang, Manfei; Huang, Xiu-Yuan; Hu, Kang; Jin, Li; Li, Hui

    2014-01-01

    The Qiangic languages in western Sichuan (WSC) are believed to be the oldest branch of the Sino-Tibetan linguistic family, and therefore, all Sino-Tibetan populations might have originated in WSC. However, very few genetic investigations have been done on Qiangic populations and no genetic evidences for the origin of Sino-Tibetan populations have been provided. By using the informative Y chromosome and mitochondrial DNA (mtDNA) markers, we analyzed the genetic structure of Qiangic populations. Our results revealed a predominantly Northern Asian-specific component in Qiangic populations, especially in maternal lineages. The Qiangic populations are an admixture of the northward migrations of East Asian initial settlers with Y chromosome haplogroup D (D1-M15 and the later originated D3a-P47) in the late Paleolithic age, and the southward Di-Qiang people with dominant haplogroup O3a2c1*-M134 and O3a2c1a-M117 in the Neolithic Age. PMID:25090432

  6. The anomalous lithium isotopic signature of Himalayan collisional zone carbonatites in western Sichuan, SW China: Enriched mantle source and petrogenesis

    NASA Astrophysics Data System (ADS)

    Tian, Shihong; Hou, Zengqian; Su, Aina; Qiu, Lin; Mo, Xuanxue; Hou, Kejun; Zhao, Yue; Hu, Wenjie; Yang, Zhusen

    2015-06-01

    Lithium concentrations and isotopic compositions of 38 carbonatites and associated syenites from the Maoniuping, Lizhuang, and Dalucao in western Sichuan, along with previously published and new Pb-Sr-Nd-C-O isotope data and whole-rock analyses, are used to constrain their mantle source and genesis. Carbonatites and syenites are characterized by extremely varying Li concentrations (0.8-120 ppm) and highly variable Li isotopic compositions (-4.5‰ to +10.8‰). Among them, the majority of the carbonatites and syenites have δ7Li values between +0.2‰ and +5.8‰, which overlap with the reported values for MORB and OIB; 3 carbonatites have higher δ7Li values between +8.7‰ and +10.8‰; 5 carbonatites and 4 syenites have lighter δ7Li values between -4.5‰ and -0.3‰. These highly variable δ7Li compositions could not have been produced by diffusive-driven isotopic fractionation of Li and thus may record the isotopic signature of the late Proterozoic subcontinental lithospheric mantle (SCLM). This paper demonstrates the existence of anomalous δ7Li within the late Proterozoic subcontinental lithospheric mantle, suggesting that the ancient SCLM beneath western Sichuan was modified by interaction with fluids derived from the subducted oceanic crust and marine sediments. The modeling curves of fluids derived from a dehydrated slab (ratios: AOC80-SED20 to AOC40-SED60) with a representative mantle composition can account for the majority of lithium compositional variations. Some samples with unusual Pb-Sr-Nd-O isotopic compositions and highly variable δ7Li compositions are affected by significant involvement of marine sediments in their source region, not contaminated by crustal materials. The carbonatites and syenites in western Sichuan were generated by the partial melting of subcontinental lithospheric mantle, which was metasomatized by the Li-rich fluids derived from the subducted oceanic crust and marine sediments. This melting was most likely triggered by a

  7. Ordovician reef-hosted Jiaodingshan Mn-Co deposit and Dawashan Mn deposit, Sichuan Province, China

    USGS Publications Warehouse

    Fan, Delian; Hein, James R.; Ye, Jie

    1999-01-01

    The Jiaodingshan Mn-Co and Dawashan Mn deposits are located in the approximately 2-m thick Daduhe unit of the Wufengian strata of Late Ordovician (Ashgill) age. Paleogeographic reconstruction places the deposits at the time of their formation in a gulf between Chengdu submarine rise and the Kangdian continent. The Jiaodingshan and Dawashan deposits occur in algal-reef facies, the former in an atoll-like structure and the latter in a pinnacle reef. Ores are mainly composed of rhodochrosite, kutnahorite, hausmannite, braunite, manganosite, and bementite. Dark red, yellowish-pink, brown, green-gray, and black ores are massive, banded, laminated, spheroidal, and cryptalgal (oncolite, stromatolite, algal filaments) boundstones. Blue, green, and red algal fossils show in situ growth positions. Samples of high-grade Jiaodingshan and Dawashan ores assay as much as 66.7% MnO. Jiaodingshan Mn carbonate ores have mean contents of Ba, Co, and Pb somewhat higher than in Dawashan ores. Cobalt is widely distributed and strongly enriched in all rock types as compared to its crustal mean content. Cobalt is correlated with Cu, Ni, and MgO in both deposits and additionally with Ba and Zn in the Dawashan deposit. The δ13C(PDB) values of Mn carbonate ores (-7.8 to -16.3‰) indicate contributions of carbon from both seawater bicarbonate and the bacterial degradation of organic matter, the latter being 33% to 68%, assuming about -24‰ for the δ13C(PDB) of the organic matter. Host limestones derived carbon predominantly from seawater bicarbonate δ1313C(PDB) of +0.2 to -7‰). NW-trending fault zones controlled development of lithofacies, whereas NE-trending fault zones provided pathways for movement of fluids. The source of Co, Ni, and Cu was mainly from weathering of mafic and ultramafic rocks on the Kangdian continent, whereas contemporaneous volcanic eruptions were of secondary importance. The reefs were likely mineralized during early diagenesis under shallow burial. The reefs

  8. Mineral dust deposition in Western Mediterranean basin

    NASA Astrophysics Data System (ADS)

    Vincent, Julie; Laurent, Benoit; Bergmatti, Gilles; Losno, Rémi; Bon Nguyen, Elisabeth; Chevaillier, Servanne; Roulet, Pierre; Sauvage, Stéphane; Coddeville, Patrice; Ouboulmane, Noura; Siour, Guillaume; Tovar Sanchez, Antonio; Massanet, Ana; Morales Baquero, Rafael; Di Sarra, Giogio; Sferlazzo, Damiano; Dulac, François; Fornier, Michel; Coursier, Cyril

    2014-05-01

    North African deserts are the world's largest sources of atmospheric mineral dust produced by aeolian erosion. Saharan dust is frequently transported toward Europe over the Mediterranean basin. When deposited in oceanic areas, mineral dust can constitute a key input of nutrients bioavailable for the oceanic biosphere. For instance, Saharan dust deposited in the in the Mediterranean Sea can be a significant source of nutrient like Fe, P and N during summer and autumn. Our objective is to study the deposition Saharan mineral dust in the western Mediterranean basin and to improve how deposition processes are parameterized in 3D regional models. To quantify the deposition flux of Saharan dust in the western Mediterranean region a specific collector (CARAGA) to sample automatically the insoluble atmospheric particle deposition was developed (LISA-ICARE) and a network of CARAGA collectors have been set up. Since 2011, eight CARAGA are then deployed in Frioul, Casset, Montandon and Ersa in France, Mallorca and Granada in Spain, Lampedusa in Italia, and Medenine in Tunisia, along a South-North gradient of almost 2000km from the North African coast to the South of Europe. We observe 10 well identified dust Saharan deposition events at Lampedusa and 6 at Mallorca for a 1-yr sampling period. These dust events are sporadic and the South-North gradient of deposition intensity and frequency is observed (the highest dust mass sampled at the stations are : 2,66 g.m-2 at Lampedusa ; 0,54 g.m-2 at Majorque ; 0,33 g.m-2 at Frioul ; 0,16 g.m-2 at Casset). The ability of the CHIMERE model to reproduce the deposition measurements is tested. The mineral dust plumes simulated over the western Mediterranean basin are also compared to satellite observations (OMI, MODIS) and in-situ measurements performed during the ChArMEx campaign and in the AERONET stations.

  9. Hydrochemistry of the Hot Springs in Western Sichuan Province Related to the Wenchuan MS 8.0 Earthquake

    PubMed Central

    Chen, Zhi; Zhou, Xiaocheng; Yi, Li; Liu, Lei; Xie, Chao; Cui, Yueju; Li, Ying

    2014-01-01

    Hydrogeochemistry of 32 hot springs in the western Sichuan Province after the Wenchuan MS 8.0 earthquake was investigated by analyzing the concentrations of cation and anion and the isotopic compositions of hydrogen and oxygen. The water samples of the hot springs were collected four times from June 2008 to April 2010. Hydrogeochemical data indicated the water samples can be classified into 9 chemical types. Values of δD and δ18O indicated that the spring waters were mainly derived from meteoric precipitation and affected by water-rock interaction and mixture of deep fluids. Concentrations of K+and SO4− of the samples from the Kangding district exhibited evident increases before the Wenchuan earthquake, indicating more supplement of deep fluids under the increase of tectonic stress. The chemical and isotopic variations of the water samples from the area closer to the epicenter area can be attributed to variation of regional stress field when the aftershock activities became weak. PMID:24892106

  10. Hydrochemistry of the hot springs in western Sichuan province related to the Wenchuan MS 8.0 earthquake.

    PubMed

    Chen, Zhi; Du, Jianguo; Zhou, Xiaocheng; Yi, Li; Liu, Lei; Xie, Chao; Cui, Yueju; Li, Ying

    2014-01-01

    Hydrogeochemistry of 32 hot springs in the western Sichuan Province after the Wenchuan MS 8.0 earthquake was investigated by analyzing the concentrations of cation and anion and the isotopic compositions of hydrogen and oxygen. The water samples of the hot springs were collected four times from June 2008 to April 2010. Hydrogeochemical data indicated the water samples can be classified into 9 chemical types. Values of δ D and δ(18)O indicated that the spring waters were mainly derived from meteoric precipitation and affected by water-rock interaction and mixture of deep fluids. Concentrations of K(+)and SO4(-) of the samples from the Kangding district exhibited evident increases before the Wenchuan earthquake, indicating more supplement of deep fluids under the increase of tectonic stress. The chemical and isotopic variations of the water samples from the area closer to the epicenter area can be attributed to variation of regional stress field when the aftershock activities became weak. PMID:24892106

  11. [Relationships between decomposition rate of leaf litter and initial quality across the alpine timberline ecotone in Western Sichuan, China].

    PubMed

    Yang, Lin; Deng, Chang-chun; Chen Ya-mei; He, Run-lian; Zhang, Jian; Liu, Yang

    2015-12-01

    The relationships between litter decomposition rate and their initial quality of 14 representative plants in the alpine forest ecotone of western Sichuan were investigated in this paper. The decomposition rate k of the litter ranged from 0.16 to 1.70. Woody leaf litter and moss litter decomposed much slower, and shrubby litter decomposed a little faster. Then, herbaceous litters decomposed fastest among all plant forms. There were significant linear regression relationships between the litter decomposition rate and the N content, lignin content, phenolics content, C/N, C/P and lignin/N. Lignin/N and hemicellulose content could explain 78.4% variation of the litter decomposition rate (k) by path analysis. The lignin/N could explain 69.5% variation of k alone, and the direct path coefficient of lignin/N on k was -0.913. Principal component analysis (PCA) showed that the contribution rate of the first sort axis to k and the decomposition time (t) reached 99.2%. Significant positive correlations existed between lignin/N, lignin content, C/N, C/P and the first sort axis, and the closest relationship existed between lignin/N and the first sort axis (r = 0.923). Lignin/N was the key quality factor affecting plant litter decomposition rate across the alpine timberline ecotone, with the higher the initial lignin/N, the lower the decomposition rate of leaf litter. PMID:27111995

  12. [Response of Picea purpurea and Abies faxoniana tree rings at different slope aspects to rapid warming in western Sichuan, China].

    PubMed

    Guo, Bin-de; Zhang, Yuan-dong; Wang, Xiao-chun

    2016-02-01

    results of multivariate analysis of variance indicated that the combined effects of slope aspect, temperature and precipitation factors were the most important limited factors for tree growth variability in western Sichuan. Therefore, we should consider the combined effects of temperature, precipitation and different slope aspects when simulating and predicting tree-growth response to the recent climate warming trend. PMID:27396105

  13. [Difference in responses of major tree species growth to climate in the Miyaluo Mountains, western Sichuan, China].

    PubMed

    Guo, Ming-ming; Zhang, Yuan-dong; Wang, Xiao-chun; Liu, Shi-rong

    2015-08-01

    To explore the responses of different tree species growth to climate change in the semi-humid region of the eastern Tibetan Plateau, we investigated climate-growth relationships of Tsuga chinensis, Abies faxoniana, Picea purpurea at an altitude of 3000 m (low altitude) and A. faxoniana and Larix mastersiana at an altitude of 4000 m (high altitude) using tree ring-width chronologies (total of 182 cores) developed from Miyaluo, western Sichuan, China. Five residual chronologies were developed from the cross-dated ring width series using the program ARSTAN, and the relationships between monthly climate variables and tree-ring index were analyzed. Results showed that the chronologies of trees at low altitudes were negatively correlated with air temperature but positively with precipitation in April and May. This indicated that drought stress limited tree growth at low altitude, but different tree species showed significant variations. T. chinensis was most severely affected by drought stress, followed by A. faxoniana and P. purpurea. Trees at high altitude were mainly affected by growing season temperature. Tree-ring index of A. faxoniana was positively correlated with monthly minimum temperature in February and July of the current year and monthly maximum temperature in October of the previous year. Radial growth of L. mastersiana was positively correlated with monthly maximum temperature in May, and negatively with monthly mean temperature in February and monthly minimum temperature in March. In recent decadal years, the climate in northeast Tibetan Plateau had a warming and drying trend. If this trend continues, we could deduce that P. purpurea should grow faster than T. chinensis and A. faxoniana at low altitudes, while A. faxoniana would benefit more from global warming at high altitudes. PMID:26685584

  14. Mercury deposits of western California: an overview

    NASA Astrophysics Data System (ADS)

    Studemeister, P. A.

    1984-07-01

    Mercury deposits in western California are near a thrust fault that separates two groups of Mesozoic rocks. The Franciscan Assemblage, a metamorphosed melange with serpentine and graywacke, is structurally overlain by the Great Valley Sequence, a sedimentary series resting on oceanic crust. These Mesozoic rocks are partly covered by volcanic and sedimentary rocks of Cenozoic age. Cinnabar with silica minerals, dolomite, native mercury, and bituminous matter occurs around the fractured margins of serpentine bodies and around hot springs that emanate from the Franciscan Assemblage. Fluid inclusions and hot springs suggest that cinnabar precipitated from CO2-H2O fluids with <2 wt% chlorine at T<250 °C. Prograde metamorphism of Mesozoic sediments expulsed mercury-bearing fluids that migrated up serpentine-related fractures and exhaled onto the surface.

  15. Provenance and tectonic-paleogeographic evolution: Constraints from detrital zircon U-Pb ages of Late Triassic-Early Jurassic deposits in the northern Sichuan basin, central China

    NASA Astrophysics Data System (ADS)

    Shao, Tongbin; Cheng, Nanfei; Song, Maoshuang

    2016-09-01

    U-Pb ages of 290 new detrital zircons from five Late Triassic-Early Jurassic sandstone samples in the northern Sichuan basin, along with other geological data, are used to constrain the sediment provenance and evaluate tectonic-paleogeographic evolution for the adjacent orogens through/from which these sediments were potentially derived. The Upper Triassic depocenter was located at the front of the Longmen Shan belt, and sediments in the western, southern and eastern Sichuan basin shared the southern North China block (NCB) and Qinling belt with the eastern Songpan-Ganzi terrane of Middle-Upper Triassic via the Longmen Shan belt, whereas the northern part of the basin was fed by dominant South Qinling belt (SQB) and northern Yangtze block and possibly subordinate southern NCB. Also, the youngest population in the northern Sichuan basin has a slightly younger age peak (∼235 Ma) than those (∼270 Ma) in other parts of the basin. During the Early Jurassic, the depocenter was still at the front of the Longmen Shan belt but only northern regions (e.g., SQB and northern Yangtze block) fed the basin. The northern Sichuan basin received less sediments from the southern NCB and more from the SQB and northern Yangtze block during the Early Jurassic than during the Late Triassic. The middle Mesoproterozoic detrital zircons, which likely originated from the North Qinling belt and northern Yangtze block where rocks with these zircons may be unexposed, occur more widely in the Lower Jurassic than in the Upper Triassic. These facts suggest that from the Late Triassic to Early Jurassic, it was increasingly difficult for sediments to transport from the NCB into the northern Sichuan basin and the provenance transferred progressively from the southern NCB to both the SQB and northern Yangtze block, implying the continuous South China block-NCB collision during that time.

  16. Tree ring-based temperature reconstruction over the past 186 years for the Miyaluo Natural Reserve, western Sichuan Province of China

    NASA Astrophysics Data System (ADS)

    Li, Zong Shan; Liu, Guo Hua; Gong, Li; Wang, Meng; Wang, Xiao Chun

    2015-05-01

    The mountain range of western Sichuan Province of China runs roughly north to south defining the eastern edge of the Tibetan Plateau, where high-resolution climate records are essential for understanding regional climatic phenomena. Unfortunately, instrumental records in this region are too short in duration to confidently gauge the long-term variability of climate change. This paper presented a temperature reconstruction for the western Sichuan Province based on a tree ring width chronology developed from a tree line site (4,150 m) of the Faxon fir ( Abies faxoniana) at the Miyaluo Natural Reserve. This reconstruction, spanning the years from 1824 to 2009, could account for 46.7 % of the actual variance of annual mean temperature during the calibration period from 1950 to 2002. The reconstruction could be essentially divided into two distinct subperiods: a relatively cold and stable period in the late nineteenth century and a relatively warm and unstable period in the twentieth century. Years 2001 and 1911 were the warmest (6.32 °C) and coldest (4.87 °C) years in the reconstruction, respectively, while 1960s (5.77 °C) and 1980s (5.08 °C) were the warmest and coldest ten consecutive years within the past 186 years. Close coupling observed with other temperature proxies (tree rings, ice cores, and glaciers) from surrounding areas emphasized the high degree of confidence in our reconstruction.

  17. NITROGEN EMISSIONS, DEPOSITION, AND MONITORING IN THE WESTERN UNITED STATES

    EPA Science Inventory

    Article presents new summary of existing data on nitrogen emissions and deposition in the western region of the United States. Study finds that nitrogen emissions and deposition have increased in the western US due to raid increases in urbanization, population, vehicle miles trav...

  18. ECOLOGICAL EFFECTS OF NITROGEN DEPOSITION IN THE WESTERN UNITED STATES

    EPA Science Inventory

    Article synthesizes existing studies (biological, ecological, biogeochemical) on the effects of nitrogen deposition to aquatic and terrestrial ecosystems in the western United States. In the western U.S, vast acreages of land are exposed to low levels of atmospheric deposition, w...

  19. Paleogene depositional framework of western Transverse ranges

    SciTech Connect

    Dickinson, W.R.

    1988-03-01

    In the western Transverse Ranges, widespread Paleogene sequences (mid-Paleocene to mid-Oligocene) accumulated to thicknesses locally in excess of 5000 m. The Paleogene basin occupied a complex forearc setting located near the offshore Franciscan trench, but distant from the inland Laramide orogenic system, where magmatism was quiescent during the interval of most rapid sedimentation. The pre-Tertiary substratum, largely masked by its Paleogene cover, was probably disrupted by transpressional and/or transtensional tectonics associated with separate episodes of mid-Cretaceous sinistral and Late Cretaceous (to Paleocene.) dextral dislocation of the continental margin. Paleogene strata include diachronous facies of intertonguing deep-marine, shallow-marine, marginal-marine, and nonmarine clastic strata representing varied depositional systems. Turbidite assemblages include both progradational and retrogradational phases of canyon-fed submarine fans and delta-fed submarine ramps. Exposed shelf-break successions were deposited offshore from strandline complexes fringing delta margins and broad coastal plains. Sparse but diagnostic nonclastic facies include local algal carbonate edifices built on isolated submarine banks, and minor lagoonal beds of algal carbonates and gypsiferous evaporites associated with emergent delta platforms. The complex Paleogene forearc basin was flanked on the northeast by Salinian basement rocks and on the southwest by a tectonic ridge of subduction complex uplifted along the Paleogene trench-slope break. The present geographic distribution of Paleogene facies tracts is fully compatible with proposed Neogene tectonic rotations of panel-like basin segments, bounded by antithetic sinistral faults within the dextral San Andreas system, as detected by recent paleomagetic investigations.

  20. Atmospheric wet deposition of sulfur and nitrogen in Jiuzhaigou National Nature Reserve, Sichuan Province, China.

    PubMed

    Qiao, Xue; Xiao, Weiyang; Jaffe, Daniel; Kota, Sri Harsha; Ying, Qi; Tang, Ya

    2015-04-01

    In the last two decades, remarkable ecological changes have been observed in Jiuzhaigou National Nature Reserve (JNNR). Some of these changes might be related to excessive deposition of sulfur (S) and nitrogen (N), but the relationship has not been quantified due to lack of monitoring data, particularly S and N deposition data. In this study, we investigated the concentrations, fluxes, and sources of S and N wet deposition in JNNR from April 2010 to May 2011. The results show that SO4(2-), NO3-, and NH4+ concentrations in the wet deposition were 39.4-170.5, 6.2-34.8, and 0.2-61.2 μeq L(-1), with annual Volume-Weighted Mean (VWM) concentrations of 70.5, 12.7, and 13.4 μeq L(-1), respectively. Annual wet deposition fluxes of SO4(2-), NO3-, and NH4+ were 8.06, 1.29, and 1.39 kg S(N)ha(-1), respectively, accounting for about 90% of annual atmospheric inputs of these species at the monitoring site. The results of Positive Matrix Factorization (PMF) analysis show that fossil fuel combustion, agriculture, and aged sea salt contributed to 99% and 83% of annual wet deposition fluxes of SO4(2-) and NO3-, respectively. Agriculture alone contributed to 89% of annual wet deposition flux of NH4+. Although wet deposition in JNNR was polluted by anthropogenic acids, the acidity was largely neutralized by the Ca2+ from crust and 81% of wet deposition samples had a pH higher than 6.00. However, acid rain mainly caused by SO4(2-) continued to occur in the wet season, when ambient alkaline dust concentration was lower. Since anthropogenic emissions have elevated S and N deposition and caused acid rain in JNNR, further studies are needed to better quantify the regional sources and ecological effects of S and N deposition for JNNR. PMID:25525712

  1. Pyroclastic deposits on the western limb of the moon

    NASA Technical Reports Server (NTRS)

    Coombs, Cassandra R.; Hawke, B. R.

    1992-01-01

    A geologic characterization is presented of 17 newly identified localized pyroclastic deposits on the western limb of the moon. The results show that lunar pyroclastic deposits are more pervasive on the western limb of the moon than once thought. The western limb dark-mantle deposits in the proximal zone are probably related to faults and fractures associated with the Cordillera ring of Orientale Basin. All the localized pyroclastic deposits on the western limb for which near-infrared reflectance spectra have been obtained exhibit parameter that allowed them to be assigned to the three spectral groups described elsewhere. Western limb pyroclastic deposits appear to represent various stages in a formational sequence in which an initial explosive phase is followed by varying amounts of mare flooding. In view of their sequential formation, both the pyroclastic and mare materials associated with individual volcanic complexes may be the products of the same parent magmas and have very similar compositions.

  2. Permian to Late Triassic evolution of the Longmen Shan Foreland Basin (Western Sichuan): Model results from both the lithospheric extension and flexure

    NASA Astrophysics Data System (ADS)

    He, Lijuan

    2014-10-01

    The lithosphere was extended during the Permian-Middle Triassic in the Yangtze Craton where the Sichuan Basin located, and then bent due to thrusting of the Longmen Shan orogen, leading to formation of the Longmen Shan Foreland Basin (Western Sichuan) during the Late Triassic Indosinian orogeny. The lateral variation of the lithospheric strength resulted by former differential extension would inevitably influence the subsequent evolution of the foreland basin. In order to investigate this, both extensional and flexural models were applied in modeling Permian-Late Triassic basin evolution. A 2D kinematic extensional model was initially developed along a profile crossing the Yangtze Craton to simulate the lithospheric thermal evolution during the Permian-Middle Triassic. Based on the thermal results, the thermal-rheological structure, as well as the effective elastic thickness of the lithosphere (Te), was then determined. Extension model show that the stretching factors decrease gradually from Songpan-Ganzi to the Sichuan Basin, leading to variable thermal-rheological structure and increased Te from west to east. Taking into account of the Te variation, a flexural model was finally constructed to investigate the evolution of the Longmen Shan Foreland Basin during the Late Triassic spanning the time period c. 227-206 Ma. Three episodes were divided according to the corresponding tectonostratigraphic units. By matching the stratigraphic observations, three phase advance distances eastward of the Longmen Shan along the Qingchuan-Maowen Fault turned out to be 18, 22, and 18 km. It implied a slow and similar thrust advance rate of 3.6 (c.227-222 Ma), 2.2 (c.222-212 Ma), and 3 mm/yr (c.212-206 Ma), respectively.

  3. Freshwater diatomite deposits in the western United States

    USGS Publications Warehouse

    Wallace, Alan R.; Frank, David G.; Founie, Alan

    2006-01-01

    Freshwater diatomite deposits in the Western United States are found in lake beds that formed millions of years ago. These diatom-rich sediments are among the Nation's largest commercial diatomite deposits. Each deposit contains billions of tiny diatom skeletons, which are widely used for filtration, absorption, and abrasives. New studies by the U.S. Geological Survey (USGS) are revealing how ancient lakes in the Western States produced such large numbers of diatoms. These findings can be used by both land-use managers and mining companies to better evaluate diatomite resources in the region.

  4. [Seasonal dynamics of soil labile nitrogen pools and net nitrogen mineralization in subalpine forests along an elevational gradient in western Sichuan, China].

    PubMed

    Yin, Rui; Xu, Zhen-Feng; Wu, Fu-Zhong; Yang, Wan-Qin; Xiong, Li; Xiao, Sa; Ma, Zhi-Liang; Li, Zhi-Ping

    2013-12-01

    The seasonal dynamics of soil labile nitrogen pools and net nitrogen mineralization of three subalpine forests along an elevation gradient (3600, 3300 and 3000 m), western Sichuan, China were examined. Obvious seasonal dynamics were found in soil labile nitrogen pools (ammonium, nitrate, microbial biomass nitrogen and dissolved organic nitrogen) and net nitrogen mineralization rate, but the seasonality varied with the measured nitrogen pools. The concentrations of soil nitrate (8.38-89.60 mg x kg(-1)) were significantly higher than those of ammonium (0.44-8.43 mg x kg(-1)) in four sampling periods (non-growing season, early, middle and late growing season). Regardless of the elevation, the rate of soil net nitrogen mineralization was negative (-0.77 to -0.56 mg x kg(-1) x d(-1)) early in the growing season, but positive in the other three periods. Except for nitrate, the contents of ammonium, microbial biomass nitrogen and dissolved organic nitrogen varied significantly with elevation and the altitude effects on those pools were dependent on seasons. In summary, soil nitrification was the major process of net soil nitrogen mineralization and soil nitrogen mineralization was not affected by elevational gradient. Soil nitrogen mineralization (0.42-0.99 mg x kg(-1) x d(-1)) in winter was considerable in this area. Relatively high inorganic nitrogen in early spring might be favorable for vegetation growth, but might also be lost from soil ecosystem through leaching. PMID:24697050

  5. The effects of China's environmental protection policies on pasture quality and the activities of small-scale herders in Songpan County, Western Sichuan.

    PubMed

    Veeck, Gregory; Li, Zhou; Yu, Fawen; Emerson, Charles

    2015-06-01

    Since 2000, there has been an ambitious governmental effort to protect China's grassland resources through new, often controversial, policies and programs backed up by massive capital investments and subsidies. The policies are intended to protect pastoral ecological systems while allowing the pasture-based husbandry sector to continue to evolve in ways that assure acceptable revenues to affected families and regions. This article reports results of a case study conducted in Songpan County of western Sichuan during the fall of 2013 specifically focused on these issues and interactions. The mixed-method research combines remotely sensed MODIS vegetation indices (EVI), livestock counts by type, and grassland area estimates at the township scale from 2000-2012, with depth interviews with local herding families and husbandry officials to determine how the husbandry sector has changed in the past 12 years under post-2000 policy interventions. Results for Songpan indicate that pasture coverage has improved slightly as grazing livestock density per hectare declined, but herders and local officials report that some of the new laws and programs have important unanticipated negative impacts on pasture quality, pasture ecology, and economic returns from herding for some families. PMID:25995138

  6. [Litter decomposition and lignocellulose enzyme activities of Actinothuidium hookeri and Cys- topteris montana in alpine timberline ecotone of western Sichuan, China].

    PubMed

    Chen, Ya-mei; He, Run-lian; Deng, Chang-chun; Yang, Wan-qin; Zhang, Jian; Yang, Lin; Liu, Yang

    2015-11-01

    The mass loss and lignocellulose enzyme activities of Actinothuidium hookeri residues and Cystopteris montana leaf litter in coniferous forest and timberline of western Sichuan, China were investigated. The results showed that both the mass loss rates of A. hookeri and C. Montana in timberline were higher than those in coniferous forest, while enzyme activities in timberline were lower than those in coniferous forest which was contrast with the hypothesis. The mass loss of two ground covers had significant differences in different seasons. The mass loss rate of A. hookeri in snow-covered season accounted for 69.8% and 83.0% of the whole year' s in timberline and coniferous forest, while that of C. montana in the growing season accounted for 82.6% and 83.4% of the whole year' s in timberline and coniferous forest, respectively. C. montana leaf litter decayed faster in the growing season, which was consistent with its higher cellulase activity in the growing season. The result illustrated that the enzymatic hydrolysis of cellulose and hemicellulose might be the main driving force for the early stage of litter decomposition. Multiple linear regression analysis showed that environmental factors and initial litter quality could explain 45.8%-85.1% variation of enzyme activity. The enzyme activities of A. hookeri and C. montana in the process of decomposition were mainly affected by the freeze-thaw cycle in snow-covered season. PMID:26915177

  7. Genetic diversity and differentiation of the rhesus macaque (Macaca mulatta) population in western Sichuan, China, based on the second exon of the major histocompatibility complex class II DQB (MhcMamu-DQB1) alleles

    PubMed Central

    2014-01-01

    Abstracts Background Rhesus macaques living in western Sichuan, China, have been separated into several isolated populations due to habitat fragmentation. Previous studies based on the neutral or nearly neutral markers (mitochondrial DNA or microsatellites) showed high levels of genetic diversity and moderate genetic differentiation in the Sichuan rhesus macaques. Variation at the major histocompatibility complex (MHC) loci is widely accepted as being maintained by balancing selection, even with a low level of neutral variability in some species. However, in small and isolated or bottlenecked populations, balancing selection may be overwhelmed by genetic drift. To estimate microevolutionary forces acting on the isolated rhesus macaque populations, we examined genetic variation at Mhc-DQB1 loci in 119 wild rhesus macaques from five geographically isolated populations in western Sichuan, China, and compared the levels of MHC variation and differentiation among populations with that previously observed at neutral microsatellite markers. Results 23 Mamu-DQB1 alleles were identified in 119 rhesus macaques in western Sichuan, China. These macaques exhibited relatively high levels of genetic diversity at Mamu-DQB1. The Hanyuan population presented the highest genetic variation, whereas the Heishui population was the lowest. Analysis of molecular variance (AMOVA) and pairwise FST values showed moderate genetic differentiation occurring among the five populations at the Mhc-DQB1 locus. Non-synonymous substitutions occurred at a higher frequency than synonymous substitutions in the peptide binding region. Levels of MHC variation within rhesus macaque populations are concordant with microsatellite variation. On the phylogenetic tree for the rhesus and crab-eating macaques, extensive allele or allelic lineage sharing is observed betweenthe two species. Conclusions Phylogenetic analyses confirm the apparent trans-species model of evolution of the Mhc-DQB1 genes in these

  8. The Features of Condensate Water and Its Guide on Gas Proudction in upper Triassic Gas Reservoir of Western Sichuan Depression, China

    NASA Astrophysics Data System (ADS)

    Shang, C.; Lou, Z.

    2012-12-01

    In upper Triassic Xujiahe Formation of western Sichuan depression, China, there developed ultrathight sandstones reservoirs, of which the mean porosity is 4.02% and the permeability mode is less than 0.1×10-3μm2. Because of the ultrathight sandstones, thick gaseous- liquid phase transition develops in the upper Trassic Xujiahe Formation. The absolute quantity of gaseous water is lager. Due to the change of temperature and pressure at the wellhead, the gaseous water in gas reservoir becomes condensate water. Therefore, the condensate water of low salinity can be widely found at the original productive process in the Xujiahe Formation reservoir, such as wells named Lian 150, Xin 851, Xin 853, Xin 856, Dayi 101, Dayi 103. The main cations are K++Na+, while the anions are HCO3- and Cl-. The main water type is CaCl2, followed by NaHCO3, Na2SO4 and MgCl2. The PH of condensate water is 5.28-8.20 with mean value 6.40. The salinity of condensate water is lower than that of formation water. The milligram equivalent (mEq) percent of ion is used to study the features of condensate water. The anions (mEq) distribution of condensate water are scattered in ternary diagram, while that of formation water concentrate upon the SO42- and Cl- endpoints. The percent of HCO3-(mEq) in condensate water is higher than that of formation water. There is no obvious difference of cations mEq percent between condensate water and formation water, which indicates that condensate water strongly affected by formation water. Through this study, condensate water may originate from formation water and then be affected by complicated physical and chemical interactions. The condensate water is affected by gas and formation water. The relationship between condensate water and gas yield is very close. The variations of water yield, salinity and ions composition can reflect the change of gas yield. Taking well Xin 856 for example, which is located in Xinchang gas felid, there exist a relationship between

  9. Paleoproterozoic gold deposits in the Bald Hill and Coyote areas, Western Tanami, Western Australia

    NASA Astrophysics Data System (ADS)

    Bagas, Leon; Huston, David L.; Anderson, James; Mernagh, Terrence P.

    2007-01-01

    Significant gold deposits in the western Tanami region of Western Australia include deposits in the Bald Hill and Coyote areas. The ca. 1,864 Ma Bald Hill sequence of turbiditic and mafic volcanic rocks hosts the Kookaburra and Sandpiper deposits and a number of smaller prospects. The ca. 1,835 Ma turbiditic Killi Killi Formation hosts the Coyote deposit and several nearby prospects. The Kookaburra deposit forms as a saddle reef within a syncline, and the Sandpiper deposit is localized within graphitic metasedimentary rocks along a limb of an anticline. Gold in these deposits is hosted by anastomosing quartz-(-pyrite-arsenopyrite) veins within quartz-sericite schist with disseminated arsenopyrite, pyrite, and marcasite (after pyrrhotite). Based on relative timing relationships with structural elements, the auriferous veins are interpreted to have been emplaced before or during the ca. 1,835-1,825 Ma Tanami Orogeny (regional D1). Gold deposition is thought to have been caused by pressure drops associated with saddle reef formation (Kookaburra) and chemical reactions with graphitic rocks (Sandpiper). The Coyote deposit, the largest in the western Tanami region, consists of a number of ore lenses localized along the limbs of the Coyote Anticline, which formed during the Tanami Orogeny. The largest lenses are associated with the Gonzalez Fault, which is located along the steeply dipping southern limb of this fold. Gold was introduced at ca. 1,790 Ma into dilatant zones that formed in local perturbations along this fault during later reactivation (regional D5) towards the end of a period of granite emplacement. Gold is associated with quartz-chlorite-pyrite-(arsenopyrite-galena-sphalerite) veins with narrow (< 5 mm) chloritic selvages. A quartz-muscovite-biotite-K-feldspar-(tourmaline-actinolite-arsenopyrite) assemblage, which is interpreted to relate to granite emplacement, overprints the regional greenschist facies metamorphic assemblage. The mineralogical similarity

  10. Appraisal of iron deposits in southern and western Turkey

    USGS Publications Warehouse

    Gair, Jacob Eugene; Capan, Ussal Z.

    1972-01-01

    Between May 20 and June 17, 1969, previously known iron deposits were examined widely at eight separate localities in western Turkey. The object of the examinations was to learn the, nature, geologic setting, and approximate size of each deposit, to review prior estimates of size, and possibly recommend additional exploratory work.. The full extent of each deposit is poorly known at the present time, so recommended additional work entails drilling, digging trenches or pits, geologic mapping or, combinations of these activities. On Qaldagi Mountain an area of about 1 sq km is capped by bredciated chert under which may be a continuous zone of mixed iron oxides and chert fragments. The thickness of the ferruginous zone is poorly known but is as much as 12 meters, in at least one place. The- ferruginous material and chert appear to have formed by the weathering of serpentine, bun this concept needs further testing. Drilling is recommended to determine the grade, thickness, and extent-of the ferruginous zone beneath the cherty cap. Inasmuch as mining by hand sorting is in progress, part of the deposit can be considered to be marginally in the category of iron reserves. The Keceborlu iron deposit consists of earthy to slightly compacted hematite and limonite mixed with small chert fragments. The surface area underlain by ferruginous rock is about 5,000 to 7,500 sq meters. The maximum known thickness of the deposit is about 7 meters. Iron appears to have been concentrated by weathering and oxidation of cherty limestone. The deposit is probably either a remnant of a once more extensive weathered cap, or a sink hole filling. The Keceborlu area warrants a low priority for further exploration, but one drill hole is recommended to test the thickness of the deposit. The iron deposits at Mellec are layered and vein-magnetite replacements of limestone. The six known deposits are discontinuous. No additional. work is recommended. ' The Gilindire Iron deposit consists of irregular

  11. Beryllium deposits of the western Seward Peninsula, Alaska

    USGS Publications Warehouse

    Sainsbury, C.L.

    1963-01-01

    Deposits of beryllium ore in the Lost River area of the western Seward Peninsula, Alaska, consist of replacement veins, pipes, and stringer lodes is limestone in a zone about 7 miles long and 2 to 3 miles wide which is faulted and intruded by dikes and stocks. The ores are remarkably alike and typically consist of the following minerals, in percent: fluorite, 45-65; diaspore, 5-10; tourmaline, 0-10; chrysoberyl, 3-10; white mica, 0-5; small amounts of hematite, sulfide minerals, manganese oxide, other beryllium minerals; and traces of minerals not yet identified. The ores generally are cut by late veinlets which are of the same mineralogy as the groundmass ore, or which consist of fluorite, white mica, and euclase. The ores are fine grained, and many of the individual mineral grains, except fluorite, are less than 1 mm in size. The beryllium content of bulk samples of ore ranges from 0.11 to 0.54 percent (0.31 to 1.50 percent BeO). High-grade nodules, composed principally of chrysoberyl, diaspore, fluorite, and mica, contain as much as 6 percent BeO. Geochemical reconnaissance has disclosed other areas of anomalous beryllium in stream sediments elsewhere on the Seward Peninsula, generally around biotite granites that have them associated with tin deposits; additional exploration probably will disclose other deposits.

  12. Metallogeny of epithermal gold deposits in the western US Cordillera

    SciTech Connect

    Duke, N.A.

    1985-01-01

    The mid-Tertiary sediment-, volcanic-, and detachment fault-hosted epithermal gold deposits (EGDs) of the western US Cordillera favor the outboard side of the tectonically thickened miogeoanticlines. Post Mesozoic accretion, this cratonic shelf-oceanic basin transition zone underwent a period of extensional uplift that thinned the brittle upper crust through listric-normal and detachment faulting, and the decoupled metamorphic infrastructure by ductile necking. The EDGs formed in the upper crust peripheral to tectonically exposed metamorphic core complexes synchronously with active extension. They demonstrate close space/time relationships to the centers of ash flow tuff eruptions that characterized this period. In general the metal concentrated in EDGs had a common source and transport mechanism. The fact that major EGDs occur along obducted oceanic thrust plates indicates that the gold was originally scavaged from oceanic successions during dewatering along the thrust structures. The metal was again mobilized in meteoric dominated hot spring systems operating within volcani-tectonic sinks occurring at ignimbrite eruptive centers. As a result, the siting of both sediment- and volcanic-hosted EGDs is controlled largely by proximity to the mid-Tertiary paleosurface. Specific controls for the precipitation of gold varies with deposit type but critical behavior of the ore-bearing fluid and/or redox reactions between migrating fluids and reduced lithology crosscut by permeable structures are primary.

  13. Buddhist Education in Sichuan

    ERIC Educational Resources Information Center

    Long, Darui

    2002-01-01

    This paper is devoted to Buddhist education in Sichuan Province with a focus on Venerable Longlian's temple. It deals with the historical development of Chinese Buddhist education and makes statistic analysis of the available data. Venerable Longlian established the Sichuan Buddhist Institute for Nuns in the 1980s. It was the first modern school…

  14. Marine intervals in Neogene fluvial deposits of western Amazonia

    NASA Astrophysics Data System (ADS)

    Boonstra, Melanie; Troelstra, Simon; Lammertsma, Emmy; Hoorn, Carina

    2014-05-01

    Amazonia is one of the most species rich areas on Earth, but this high diversity is not homogeneous over the entire region. Highest mammal and tree-alpha diversity is found in the fluvio-lacustrine Pebas system, a Neogene wetland associated with rapid radiation of species. The estuarine to marine origin of various modern Amazonian fish, plants, and invertebrates has been associated with past marine ingressions into this freshwater Pebas system. The exact nature and age of these invasions is, however, debated. Here we present new evidence from fluvial and fluvio-lacustrine deposits of Neogene age in southeast Colombia, that point to periods of widespread marine conditions in western Amazonia. Our evidence is based on an analysis of marine palynomorphs, such as organic linings of foraminifera and dinoflagellate cysts, present in dark sandy clay sediments that outcrop along the Caqueta and Amazon rivers. Characteristically, the foraminiferal linings can be assigned to three benthic morphotypes only, e.g. Ammonia, Elphidium and Trochammina. This low diversity assemblage is associated with estuarine/marginal marine conditions. No distinct marine elements such as shelf or planktonic species were encountered. The observed foraminiferal linings and dinocyst assemblages are typical for a (eutrophic) shallow marine environment, suggesting that the Pebas freshwater wetland system occasionally changed to (marginal) marine. Although some reworked elements are found, a typical Neogene dinocyst taxon is commonly found supporting in situ deposition. Sedimentological features typical for tidal conditions that are reported for sites in Peru and northeastern Brazil likely relate to these marine ingressions. Sea level changes as well as foreland basin development related to Andes formation may have facilitated the entry of marine water during the Neogene.

  15. Critical Metals In Western Arctic Ocean Ferromanganese Mineral Deposits

    NASA Astrophysics Data System (ADS)

    Hein, J. R.; Spinardi, F.; Conrad, T. A.; Conrad, J. E.; Genetti, J.

    2013-12-01

    Little exploration for minerals has occurred in the Arctic Ocean due to ice cover and the remote location. Small deposits of seafloor massive sulfides that are rich in copper and zinc occur on Gakkel Ridge, which extends from Greenland to the Laptev Sea, and on Kolbeinsey and Mohns ridges, both located between Greenland and mainland Europe. However, rocks were recently collected by dredge along the western margin of the Canada Basin as part of the U.S. Extended Continental Shelf (ECS) program north of Alaska. Sample sites include steep escarpments on the Chukchi Borderland, a newly discovered seamount informally named Healy seamount, the southern part of Alpha-Mendeleev Ridge, and several basement outcrops in Nautilus Basin. These dredge hauls yielded three types of metal-rich mineralized deposits: ferromanganese crusts, ferromanganese nodules, and hydrothermal iron and manganese deposits. Chemical analyses of 43 crust and nodule samples show high contents of many critical metals needed for high-technology, green-technology, and energy and military applications, including cobalt (to 0.3 wt.%), vanadium (to 0.12 wt.%), zirconium (to 459 grams/tonne=ppm), molybdenum (to 453 g/t), the rare-earth elements (including scandium and yttrium; yttrium to 229 g/t), lithium (to 205 g/t), tungsten (to 64 g/t), and gallium (to 26 g/t). The metal contents of these Arctic Ocean crusts and nodules are comparable to those found throughout the global ocean, however, these Arctic Ocean samples are the first that have been found to be enriched in rare metal scandium. The metal contents of these samples indicate a diagenetic component. Crusts typically form by precipitation of metal oxides solely from seawater (hydrogenetic) onto rock surfaces producing a pavement, whereas nodules form by accretion of metal oxides, from both seawater and pore waters (diagenetic), around a nucleus on the surface of soft sediment. The best evidence for this diagenetic input to the crusts is that crusts

  16. Measuring and monitoring snow deposition, properties and processes in mountain catchments of Western North America

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Patterns of snow deposition, and the distribution of snow properties and processes in mountainous regions of Western North America are highly heterogeneous. Wind and topographic structure control snow deposition, causing tremendous spatial heterogeneity in the distribution of the snowcover and the ...

  17. Coking-coal deposits of the western United States

    USGS Publications Warehouse

    Berryhill, Louise R.; Averitt, Paul

    1951-01-01

    Geohydrologic systems in the Anadarko basin in the central United States are controlled by topography, climate, geologic structures, and aquifer hydraulic properties, all of which are the result of past geologic and hydrologic processes, including tectonics and diagenesis. From Late Cambrian through Middle Ordovician time, a generally transgressive but cyclic sea covered the area. The first deposits were permeable sand, followed by calcareous mud. During periods of sea transgression, burial diagenesis decreased porosity and permeability. During Pennsylvanian time, rapid sedimentation accompanied rapid subsidence in the Anadarko basin. A geopressure zone probably resulted when sediments with little permeability trapped depositional water in Lower Pennsylvanian sands. Burial diagenesis included compaction and thermal alteration of deeply buried organic material, which released carbon dioxide, water, and hydrocarbons. By Middle Pennsylvanian time, the sea had submerged most of the central United States, including the Ozarks, as tectonic activity reached its maximum. During Late Pennsylvanian and Early Permian time, the Ouachita uplift had been formed and was higher than the Ozarks. Uplift was accompanied by a regional upward tilt toward the Ouachita-Ozarks area; the sea receded westward, depositing large quantities of calcareous mud and clay, and precipitating evaporitic material in the restricted-circulation environment. By the end of Permian time, > 20,000 ft of Pennsylvanian and Permian sediments had been deposited in the Anadarko basin. These thick sediments caused rapid and extreme burial diagensis, including alteration of organic material During Permian time in the Ozarks area, development of the Ozark Plateau aquifer system commenced in the permeable Cambrian-Mississippian rocks near the St. Francois Mountains as the Pennsylvanian confining material was removed. Since Permian time, uplift diagenesis has been more active than burial diagenesis in the Anadarko

  18. Distribution of atmospheric marine salt depositions over Continental Western Europe.

    PubMed

    Delalieux, F; van Grieken, R; Potgieter, J H

    2006-06-01

    This contribution describes the distribution of marine salt aerosols in Belgium, France and Spain, as obtained from applying a kriging model to a set of data. The data was collected over a period of nine years and included wet as well as dry deposition results. It was found that the concentration of the salt particles decreased the fastest in Spain and the slowest in Belgium with increasing inland distance from the sea. These findings have implications for the degradation of monuments and historical buildings as a result of salt attack and ingress that often accompany degradation due to air pollution. PMID:16772114

  19. Geological setting and mineralization model for the Cleo gold deposit, Eastern Goldfields Province, Western Australia

    NASA Astrophysics Data System (ADS)

    Brown, Suzanne M.; Groves, David I.; Newton, Philip G.

    2002-10-01

    The Cleo gold deposit, containing 4.25 Moz Au (37.1 Mt at 3.6 g/t), is the western part of a continuous orebody divided by a north-south tenement boundary. The eastern part is known as Sunrise, and together the Cleo and Sunrise deposits contain nearly 8 Moz Au in resources and past production. The focus of this study is the Cleo deposit, located 50 km south of Laverton in the Eastern Goldfields Province of the Yilgarn Craton of Western Australia, hosted in an Archean sequence dominated by volcaniclastic rocks. The Sunrise Shear Zone divides the sequence into hanging wall and footwall components. The gently north-west-dipping shear zone controls the orientation of shear-zone parallel ore zones, which characteristically involve pyrite replacement of magnetite in banded iron formation. Steeply-dipping multistage veins in the hanging wall and footwall define the Western Lodes, ore zones that are oriented parallel to adjacent rhyodacite-porphyry dikes. Western Lode veins are developed in all rock types, and commonly contain free gold, as well as pyrite, arsenopyrite, tennantite and chalcopyrite. In the footwall block, the margins of steeply east-dipping rhyodacite porphyry dikes form the main control on localization of the Western Lodes. In the hanging wall, the Western Lodes parallel a porphyry dike, both structures exploiting a favourable orientation in the stratigraphic sequence. Rhyodacite porphyry dikes exhibit strained margins in the Sunrise Shear Zone. Gold-bearing Western Lodes veins cut porphyry dikes and cut the Sunrise Shear Zone with minimal offset. The association of the ~2,675 Ma rhyodacite porphyry dikes with the Western Lodes ore zones is caused by the structurally favourable orientation of the dikes, and not to any direct genetic relationship between rhyodacite porphyry magma and ore fluids, as the latter post-dated the former.

  20. Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris

    NASA Technical Reports Server (NTRS)

    1997-01-01

    On October 26, 1997, MOC took this image of Mars 10 minutes after its closest approach to the planet (1:46 AM PST). The view shows the floor of western Ganges Chasma (7.8oS 51.8oW), covering an area 2.6 km (1.6 miles) wide by 45.4 km (28.2 miles) long at a resolution of 5 by 7.4 meters (16.4 by 24.3 feet) per picture element. The local time on Mars when the picture was taken was 4:35 PM.

    The center image (available at higher resolution as PIA01028) shows the northern portion of the area inscribed in the left image. The right image (PIA01029) shows the southern portion.

    Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  1. Geology, distribution, and classification of gold deposits in the western Qinling belt, central China

    USGS Publications Warehouse

    Mao, J.; Qiu, Y.; Goldfarb, R.J.; Zhang, Z.; Garwin, S.; Fengshou, R.

    2002-01-01

    Gold deposits of the western Qinling belt occur within the western part of the Qinling-Dabie-Sulu orogen, which is located between the Precambrian North China and Yangtze cratons and east of the Songpan-Ganzi basin. The early Paleozoic to early Mesozoic orogen can be divided into northern, central, and southern zones, separated by the Shangdan and Lixian-Shanyang thrust fault systems. The northern zone consists of an early Paleozoic arc accreted to the North China craton by ca. 450 Ma. The central zone, which contains numerous orogenic gold deposits, is dominated by clastic rocks formed in a late Paleozoic basin between the converging cratonic blocks. The southern zone is characterized by the easternmost exposure of Triassic sedimentary rocks of the Songpan-Ganzi basin. These Early to Late Triassic turbidities, in part calcareous, of the immense Songpan-Ganzi basin also border the western Qinling belt to the west. Carlinlike gold deposits are abundant (1) along a westward extension of the southern zone defined by a window of early Paleozoic clastic rocks extending into the basin, and (2) within the easternmost margin of the basinal rocks to the south of the extension, and in adjacent cover rocks of the Yangtze craton. Triassic and Early Jurassic synkinematic granitoids are widespread across the western Qinling belt, as well as in the Songpan-Ganzi basin. Orogenic lode gold deposits along brittle-ductile shear zones occur within greenschist-facies, highly deformed, Devonian and younger clastic rocks of the central zone. Mainly coarse-grained gold, along with pyrite, pyrrhotite, arsenopyrite, and minor base metal sulfides, occur in networks of quartz veinlets, brecciated wall rock, and are dissminated in altered wall rock. Isotopic dates suggest that the deposits formed during the Late Triassic to Middle Jurassic as the leading edge of the Yangtze craton was thrust beneath rocks of the western Qinling belt. Many gold-bearing placers are distributed along the river

  2. ATLAS OF AIR QUALITY AND DEPOSITION IN OR NEAR FORESTS OF THE WESTERN UNITED STATES

    EPA Science Inventory

    An atlas of air quality and deposition data has been compiled to make air pollution data and information more accessible to biologists and ecologists working in western forests. ata from the 1985 National Acid precipitation Assessment program Emission Inventory are used to charac...

  3. Variability of mineral dust deposition in the western Mediterranean basin and south-east of France

    NASA Astrophysics Data System (ADS)

    Vincent, Julie; Laurent, Benoit; Losno, Rémi; Bon Nguyen, Elisabeth; Roullet, Pierre; Sauvage, Stéphane; Chevaillier, Servanne; Coddeville, Patrice; Ouboulmane, Noura; di Sarra, Alcide Giorgio; Tovar-Sánchez, Antonio; Sferlazzo, Damiano; Massanet, Ana; Triquet, Sylvain; Morales Baquero, Rafael; Fornier, Michel; Coursier, Cyril; Desboeufs, Karine; Dulac, François; Bergametti, Gilles

    2016-07-01

    Previous studies have provided some insight into the Saharan dust deposition at a few specific locations from observations over long time periods or intensive field campaigns. However, no assessment of the dust deposition temporal variability in connection with its regional spatial distribution has been achieved so far from network observations over more than 1 year. To investigate dust deposition dynamics at the regional scale, five automatic deposition collectors named CARAGA (Collecteur Automatique de Retombées Atmosphériques insolubles à Grande Autonomie in French) have been deployed in the western Mediterranean region during 1 to 3 years depending on the station. The sites include, from south to north, Lampedusa, Majorca, Corsica, Frioul and Le Casset (southern French Alps). Deposition measurements are performed on a common weekly period at the five sites. The mean dust deposition fluxes are higher close to the northern African coasts and decrease following a south-north gradient, with values from 7.4 g m-2 year-1 in Lampedusa (35°31' N, 12°37' E) to 1 g m-2 year-1 in Le Casset (44°59' N, 6°28' E). The maximum deposition flux recorded is of 3.2 g m-2 wk-1 in Majorca with only two other events showing more than 1 g m-2 wk-1 in Lampedusa, and a maximum of 0.5 g m-2 wk-1 in Corsica. The maximum value of 2.1 g m-2 year-1 observed in Corsica in 2013 is much lower than existing records in the area over the 3 previous decades (11-14 g m-2 year-1). From the 537 available samples, 98 major Saharan dust deposition events have been identified in the records between 2011 and 2013. Complementary observations provided by both satellite and air mass trajectories are used to identify the dust provenance areas and the transport pathways from the Sahara to the stations for the studied period. Despite the large size of African dust plumes detected by satellites, more than 80 % of the major dust deposition events are recorded at only one station, suggesting that the dust

  4. Variability of mineral dust deposition in the western Mediterranean basin and South-East of France

    NASA Astrophysics Data System (ADS)

    Vincent, J.; Laurent, B.; Losno, R.; Bon Nguyen, E.; Roullet, P.; Sauvage, S.; Chevaillier, S.; Coddeville, P.; Ouboulmane, N.; di Sarra, A. G.; Tovar-Sánchez, A.; Sferlazzo, D.; Massanet, A.; Triquet, S.; Morales Baquero, R.; Fornier, M.; Coursier, C.; Desboeufs, K.; Dulac, F.; Bergametti, G.

    2015-12-01

    Previous studies have provided some insight into the Saharan dust deposition at a few specific locations from observations over long time periods or intensive field campaigns. However, no assessment of the dust deposition temporal variability in connection with its regional spatial distribution has been achieved so far from network observations over more than one year. To investigate dust deposition dynamics at the regional scale, five automatic deposition collectors named CARAGA ("Collecteur Automatique de Retombées Atmosphériques insolubles à Grande Autonomie" in French) have been deployed in the western Mediterranean region during one to three years depending on the station. The sites include, from South to North, Lampedusa Isl., Mallorca Isl., Corsica Isl., Frioul Isl. and Le Casset (South of French Alps). Deposition measurements are performed on a common weekly period at the 5 sites. The mean Saharan dust deposition fluxes are higher close to the North African coasts and decrease following a South to North gradient, with values from 7.4 g m-2 yr-1 in Lampedusa (35°31' N-12°37' E) to 1 g m-2 yr-1 in Le Casset (44°59' N-6°28' E). The maximum deposition flux recorded is of 3.2 g m-2 wk-1 in Mallorca with only 2 other events showing more than 1 g m-2 wk-1 in Lampedusa, and a maximum of 0.5 g m-2 wk-1 in Corsica. The maximum value of 2.1 g m-2 yr-1 observed in Corsica in 2013 is much lower than existing records in the area over the 3 previous decades (11-14 g m-2 yr-1). From the 537 available samples, ninety eight major Saharan dust deposition events have been identified in the records between 2011 and 2013. Complementary observations provided by both satellite and air mass trajectories are used to identify the dust provenance areas and the transport pathways from the Sahara to the stations. Despite the large size of African dust plumes detected by satellites, more than eighty percent of the major dust deposition events are recorded at only one station

  5. Nutrient and trace metals atmospheric deposition in the western Mediterranean: source apportionment

    NASA Astrophysics Data System (ADS)

    Desboeufs, Karine; Bon Nguyen, Elisabeth; Simeoni, Pasquale; Dulac, François

    2015-04-01

    Mediterranean Sea is a typical LNLC region particularly well adapted to assess the role of ocean-atmosphere exchanges. Throughout the summer stratification period when diffusion through the thermocline is low, atmospheric inputs become the main external source of nutrients to the surface open waters of the MS, mostly by wet deposition in the western basin.Here, we show a 3-yr time continuous series of nutrient (N, P) and trace metals (Cr, Cu, Fe, P, V, Zn) total deposition fluxes in Corsica. Between March 2008 and May 2011, a monitoring station was operated with a weekly sampling time step at Galeria (42.44°N; 8.65°E) on the western coast of Corsica in the framework of the projects DUNE (a Dust Experiment in a Low Nutrient Low Chlorophyll Ecosystem) and then ChArMEx (the Chemistry-Aerososl Mediterranean Experiment). Monthly fluxes were measured to assess the temporal variability of the measured elements over the Western Mediterranean. Nutrients deposition presented a clear seasonal pattern which was different for each studied nutrients, emphasizing a difference of sources for the nutrients. The results show no dust event larger than 0.68 g m-2 so that the maximum yearly flux was among the lowest ever observed in Corsica (1.7 g m-2 y-1). One dust deposition event could contribute up to 30% of yearly deposition fluxes of nutrient and trace metals, confirming the high temporal variability of atmospheric deposition. However a source apportionment work via statistical methods shows that the yearly deposition fluxes of considered nutrient and trace metals were dominated by anthropogenic sources, except for Fe. Acknowledgements: DUNE project was funded by ANR. ChArMEx (http://charmex.lsce.ipsl.fr) is funded by CNRS/INSU, ADEME, CEA and Météo-France in the framework of the programme MISTRALS (http://www.mistrals-home.org)

  6. One new species of the genus Nigrimacula Shi, Bian & Zhou, 2016 (Orthoptera: Meconematinae) from Sichuan, China.

    PubMed

    Wang, Hai-Jian; Shi, Fu-Ming

    2016-01-01

    The paper describels one new species, i.e. Nigrimacula sichuanensis Wang & Shi, sp. nov. from Sichuan, China, and provides photographs of morphological characters. The type material is deposited in the Museum of Hebei University. PMID:27395697

  7. Are climate warming and enhanced atmospheric deposition of sulfur and nitrogen threatening tufa landscapes in Jiuzhaigou National Nature Reserve, Sichuan, China?

    PubMed

    Qiao, Xue; Du, Jie; Lugli, Stefano; Ren, Jinhai; Xiao, Weiyang; Chen, Pan; Tang, Ya

    2016-08-15

    Massive deposition of calcium carbonate in ambient temperature waters (tufa) can form magnificent tufa landscapes, many of which are designated as protected areas. However, tufa landscapes in many areas are threatened by both local anthropogenic activities and climate change. This study, for the first time, posed the question whether the tufa landscape degradation (characterized by tufa degradation and increased biomass of green algae) in Jiuzhaigou National Nature Reserve of China is partially caused by regional air pollution and climate warming. The results indicate that wet deposition (including rain and snow) polluted by anthropogenic SO2, NOx, and NH3 emissions dissolves exposed tufa and may considerably reduce tufa deposition rate and even cause tufa dissolution within shallow waters. These effects of wet deposition on tufa enhanced as pH of wet deposition decreased from 8.01 to 5.06. Annual Volume Weighted Mean concentration of reactive nitrogen (including NH4(+) and NO3(-)) in wet deposition (26.1μmolL(-1)) was 1.8 times of the corresponding value of runoff (14.8μmolL(-1)) and exceeded China's national standard of total nitrogen in runoff for nature reserves (14.3μmolL(-1)), indicating a direct nitrogen fertilization effect of wet deposition on green algae. As water temperature is the major limiting factor of algal growth in Jiuzhaigou and temperature in the top layer (0-5cm) of runoff (depth<1m, no canopy coverage of trees and shrubs) was significantly higher at the sites with increased biomass of green algae (p<0.05), climate warming in this region would favor algal growth. In sum, this study suggests that climate warming and enhanced sulfur and nitrogen deposition have contributed to the current degradation of tufa landscape in Jiuzhaigou, but in order to quantify the contributions, further studies are needed, as many other anthropogenic and natural processes also influence tufa landscape evolution. PMID:27110983

  8. Synthesis of late Paleozoic and Mesozoic eolian deposits of the Western Interior of the United States

    NASA Astrophysics Data System (ADS)

    Blakey, Ronald C.; Peterson, Fred; Kocurek, Gary

    1988-04-01

    Late Paleozoic and Mesozoic eolian deposits include rock units that were deposited in ergs (eolian sand seas), erg margins and dune fields. They form an important part of Middle Pennsylvanian through Upper Jurassic sedimentary rocks across the Western Interior of the United States. These sedimentary rock units comprise approximately three dozen major eolian-bearing sequences and several smaller ones. Isopach and facies maps and accompanying cross sections indicate that most eolian units display varied geometry and complex facies relations to adjacent non-eolian rocks. Paleozoic erg deposits are widespread from Montana to Arizona and include Pennsylvanian formations (Weber, Tensleep, Casper and Quadrant Sandstones) chiefly in the Northern and Central Rocky Mountains with some deposits (Hermosa and Supai Groups) on the Colorado Plateau. Lower Permian (Wolfcampian) erg deposits (Weber, Tensleep, Casper, Minnelusa, Ingleside, Cedar Mesa, Elephant Canyon, Queantoweap and Esplanade Formations) are more widespread and thicken into the central Colorado Plateau. Middle Permian (Leonardian I) erg deposits (De Chelly and Schnebly Hill Formations) are distributed across the southern Colorado Plateau on the north edge of the Holbrook basin. Leonardian II erg deposits (Coconino and Glorieta Sandstones) are slightly more widespread on the southern Colorado Plateau. Leonardian III erg deposits formed adjacent to the Toroweap-Kaibab sea in Utah and Arizona (Coconino and White Rim Sandstones) and in north-central Colorado (Lyons Sandstone). Recognized Triassic eolian deposits include major erg deposits in the Jelm Formation of central Colorado-Wyoming and smaller eolian deposits in the Rock Point Member of the Wingate Sandstone and upper Dolores Formation, both of the Four Corners region. None of these have as yet received a modern or thorough study. Jurassic deposits of eolian origin extend from the Black Hills to the southern Cordilleran arc terrain. Lower Jurassic intervals

  9. CO2 deposition over the multi-year ice of the western Weddell Sea

    NASA Astrophysics Data System (ADS)

    Zemmelink, H. J.; Delille, B.; Tison, J. L.; Hintsa, E. J.; Houghton, L.; Dacey, J. W. H.

    2006-07-01

    Field measurements by eddy correlation (EC) indicate an average uptake of 0.6 g CO2 m-2 d-1 by the ice-covered western Weddell Sea in December 2004. At the same time, snow that covers ice floes of the western Weddell Sea becomes undersaturated with CO2 relative to the atmosphere during early summer. Gradients of CO2 from the ice to the atmosphere do not support significant diffusive fluxes and are not strong enough to explain the observed CO2 deposition. We hypothesize that the transport of air through the snow pack is controlled by turbulence and that undersaturation of CO2 is caused by biological productivity at the ice-snow and snow-atmosphere interface. The total carbon uptake by the multi-year ice zone of the western Weddell Sea in December could have been as high as 6.6 Tg C y-1.

  10. Quaternary geology and sapphire deposits from the BO PHLOI gem field, Kanchanaburi Province, Western Thailand

    NASA Astrophysics Data System (ADS)

    Choowong, Montri

    2002-01-01

    One of the most famous blue sapphire deposits in Thailand and SE Asia is from the Bo Phloi District, Kanchanaburi Province, Western Thailand. This paper presents the results of our gemstone investigation as well as establishing the Bo Phloi depositional sequence as one of the Quaternary Type Sections in the region. Relationships among the sedimentology, depositional sequences and geomorphology were investigated in order to understand the gemstone depositional features. Sedimentary structures and textures of the sequences show that the deposition of gemstones is related genetically to fluvial processes. Gemstones are recognized in floodplain and low terrace deposits where gemstone paystreaks concentrate mostly inside layers of gravel beds and foreset-bedded gravels lithofacies. C-14 dating of wood and peat within gemstone-bearing layers indicated that the deposit formed during the middle to late Pleistocene. The gemstone-bearing gravel bed defines a north-south trend along the incised palaeo-channel of an ancient braided river system in the middle part of the basin.

  11. The geologic relationships of industrial mineral deposits and asbestos in the western united states

    USGS Publications Warehouse

    VanGosen, B.S.

    2009-01-01

    In recent years, U.S. regulatory agencies have placed emphasis on identifying and regulating asbestos dust exposures in the mining environment, with a particular focus upon industrial mineral deposits in which asbestos occurs as an accessory mineral. Because asbestos minerals form in specific geologic environments, only certain predictable types of industrial mineral deposits can potentially host asbestos mineralization. By applying a basic knowledge of asbestos geology, the costly and time consuming efforts of asbestos monitoring and analyses can be directed towards those mineral deposit types most likely to contain asbestos mineralogy, while saving efforts on the mineral deposits that are unlikely to contain asbestos. While the vast majority of industrial mineral deposits in the Western United States are asbestos-free, there are several types that can, in some instances, host asbestos mineralization, or be closely associated with it. These industrial mineral deposits include a few types of aggregate, dimension, and decorative stone, and some deposits of chromite-nickel, magnesite, nepheline syenite, olivine, rare earth elements, talc, vermiculite, and wollastonite.

  12. Biogeochemical and Ecological Effects of Nitrogen Deposition in Western North America

    NASA Astrophysics Data System (ADS)

    Fenn, M. E.

    2003-12-01

    The unique geographic, demographic, climatic and edaphic conditions of the West determine N deposition rates and biogeochemical and ecological responses to N deposition. In the western United States large regions are exposed to low N deposition levels with interspersed hotspots of elevated N deposition near urban areas or large agricultural emissions sources. Nitrogen emissions also contribute to ozone formation and regional haze and visibility impairment, the latter an effect that is observed in remote sites including several high profile national parks and wilderness areas. Recent studies suggest that N enrichment impacts are generally more important in western terrestrial systems than soil acidification effects. In the Pacific Northwest, California and Colorado sensitive organisms such as lichens and phytoplankton demonstrate deleterious biological effects with N deposition levels as low as 3-8 kg ha-1 yr-1. Increased streamwater nitrate export has been reported from southern California forests and chaparral catchments, high elevation watersheds in the Colorado Front Range, and in the most exposed regions of the southwestern Sierra Nevada. Evidence suggests that in some regions N deposition alters plant community composition, decreases mycorrhizal diversity, and also increases biomass accumulation, carbon allocation patterns and fire frequency. Several factors predispose Western semiarid ecosystems to N saturation as will be demonstrated by the San Bernardino Mountains case study (southern California). Edaphic conditions generally favor high nitrification rates relative to N mineralization. Nitrate from nitrification and atmospheric deposition accumulates in soil and on plant surfaces during prolonged dry periods. Under conditions of chronic N deposition, the N cycle becomes highly open in nature as excess N is exported in runoff and as gaseous emissions from soil. Actively nitrifying soils and temporal asynchrony between the period of plant N demand and nitrate

  13. Mega debris flow deposits on the western Wilkes Land margin, East Antarctica

    USGS Publications Warehouse

    Donda, F.; O'Brien, P.E.; De Santis, L.; Rebesco, M.; Brancolini, Giuliano

    2007-01-01

    Multichannel seismic data collected off Western Wilkes Land (East Antarctica) reveal the occurrence of mega debris flow deposits on the lower slope and rise that were formed throughout the Miocene. Commonly, debris flow units are separated by thin deposits of well-stratified facies, interpreted as predominantly glaciomarine mixed contouritic and distal turbidite deposits. These units could act as weak layers and could have played a major role in the slope instability. High sedimentation rates, due to large amounts of sediment delivered from a temperate, wet-based ice sheet, constituted a key factor in the sediment failures. The main trigger mechanism would probably have been earthquakes enhanced by isostatic rebound following major ice sheet retreats.

  14. The economic potential of El-Gedida glauconite deposits, El-Bahariya Oasis, Western Desert, Egypt

    NASA Astrophysics Data System (ADS)

    El-Habaak, Galal; Askalany, Mohamed; Faraghaly, Mohamed; Abdel-Hakeem, Mahmoud

    2016-08-01

    The mining work at El-Gedida iron mine, El-Bahariya Oasis, in the Western Desert of Egypt extracts commercial iron ore deposits without attention paid to the large glauconite deposits overlying these iron ore deposits. For this reason, the present paper aims at evaluating and attracting the attention to these glauconite deposits as alternative potassium fertilizers. The study was achieved by investigating mineralogical, physical and chemical properties of the green deposits. Mineralogical and physical properties involved the determination of glauconite pellets content in different grain size fractions relative to impurities and the analysis of the percentage of clay matrix and grain size distribution. Different pre-treatment strategies and methods including comminution, sieving, magnetic separation, and X-ray diffraction were used for investigating those mineralogical and physical properties. On the other hand, chemical analyses included potassium content, heavy metal concentrations, and pH and salinity measurements. The major elements and trace elements were measured using ICP-OES and the pH was measured using a pH conductometer. Moreover, this study investigated the nature of grain boundaries and the effect of sieving on glauconite beneficiation. Results of this study suggest that El-Gedida glauconite deposits are mineralogically, physically and chemically suitable for exploitation and can be beneficiated for use as an alternative potassium fertilizer.

  15. Geodynamic setting of mineralization of Mississippi Valley-type deposits in world-class Sichuan-Yunnan-Guizhou Zn-Pb triangle, southwest China: Implications from age-dating studies in the past decade and the Sm-Nd age of Jinshachang deposit

    NASA Astrophysics Data System (ADS)

    Zhang, Changqing; Wu, Yue; Hou, Lin; Mao, Jingwen

    2015-05-01

    The Sichuan-Yunnan-Guizhou (S-Y-G) Zn-Pb triangle is a world-class metallogenic belt in southwestern China that contains hundreds of carbonate-hosted giant-to-small epigenetic Zn-Pb deposits. Here, we provide an overview of the ore geology, geochemistry and ore-forming fluids of the major Zn-Pb deposits in this area. These deposits are most likely Mississippi Valley-type (MVT) deposits that formed as a result of the regional migration of basinal brines along large fault systems and more minor secondary structures. The Sm-Nd age (201 ± 6.2 Ma) of ore-stage fluorite from the Jinshachang Zn-Pb deposit, within northeast Yunnan province, China, reveals this deposit formed during the Late Triassic, consistent with the majority of the published isotopic ages for other Zn-Pb deposits in the S-Y-G MVT triangle. These fluorite samples have initial 87Sr/86Sr ratios of 0.711385-0.711463 and εNd values of -8.4 to -8.7, confirming the basin-related nature of the mineralizing fluids. Published geochronological data combined with basic features of MVT deposits (e.g., geology, geochemistry, and ore-forming fluids) and the geological evolution of the study area has enabled us to develop a model for the Zn-Pb mineralization, where this word-class MVT belt has formed as a result of the regional-scale migration of basinal fluids coincident with tectonic activity along ore-controlling structures (e.g., thrust-fold systems). Both the fluid migration and the tectonic activity were probably triggered by the late Indosinian Orogeny, which in turn was a response to the closure of the Paleo-Tethys Ocean.

  16. Western Pacific atmospheric nutrient deposition fluxes, their impact on surface ocean productivity

    NASA Astrophysics Data System (ADS)

    Martino, M.; Hamilton, D.; Baker, A. R.; Jickells, T. D.; Bromley, T.; Nojiri, Y.; Quack, B.; Boyd, P. W.

    2014-07-01

    The atmospheric deposition of both macronutrients and micronutrients plays an important role in driving primary productivity, particularly in the low-latitude ocean. We report aerosol major ion measurements for five ship-based sampling campaigns in the western Pacific from ~25°N to 20°S and compare the results with those from Atlantic meridional transects (~50°N to 50°S) with aerosols collected and analyzed in the same laboratory, allowing full incomparability. We discuss sources of the main nutrient species (nitrogen (N), phosphorus (P), and iron (Fe)) in the aerosols and their stoichiometry. Striking north-south gradients are evident over both basins with the Northern Hemisphere more impacted by terrestrial dust sources and anthropogenic emissions and the North Atlantic apparently more impacted than the North Pacific. We estimate the atmospheric supply rates of these nutrients and the potential impact of the atmospheric deposition on the tropical western Pacific. Our results suggest that the atmospheric deposition is P deficient relative to the needs of the resident phytoplankton. These findings suggest that atmospheric supply of N, Fe, and P increases primary productivity utilizing some of the residual excess phosphorus (P*) in the surface waters to compensate for aerosol P deficiency. Regional primary productivity is further enhanced via the stimulation of nitrogen fixation fuelled by the residual atmospheric iron and P*. Our stoichiometric calculations reveal that a P* of 0.1 µmol L-1 can offset the P deficiency in atmospheric supply for many months. This study suggests that atmospheric deposition may sustain ~10% of primary production in both the western tropical Pacific.

  17. Mixtures of clays and sulfates within deposits in western Melas Chasma, Mars

    NASA Astrophysics Data System (ADS)

    Weitz, Catherine M.; Noe Dobrea, Eldar; Wray, James J.

    2015-05-01

    We have utilized several data sets from multiple spacecraft that have been acquired over a continuous observation campaign across the southwestern Melas Chasma region of Mars. The blocky deposit observed on the chasma floor and on portions of the southern wallrock consists of mixtures of light- and medium-toned materials that exhibit displacement structures consistent with transport down the wallrock and onto the chasma floor. CRISM visible and near-infrared reflectance spectra of the light-toned blocks suggest mixtures of nontronite, jarosite, Al-clays, hydrated silica, and/or an acid leached clay. The medium-toned blocks typically lack spectral features or exhibit signatures of polyhydrated sulfates. Bright layered mounds embayed by blocky deposit materials display spectra consistent with Ca-sulfates (gypsum and/or bassanite) that may have resulted from precipitation of less soluble Ca-rich minerals during ponding and evaporation of dilute fluids along the western chasma floor. Draping across some wallrock slopes is a light-toned deposit that sometimes overlies a blocky, layered, and spectrally bland medium-toned deposit. The light-toned deposit exhibits spectra consistent with mixtures of materials that may include jarosite, acid-leached clays, silica, poorly crystalline clays, and polyhydrated sulfates. Hesperian-age valleys dissect the medium-toned deposit along some wallrock slopes and may be partially filled in by light-toned deposits. The draping nature of these deposits can best be explained by airfall, either volcanic ash or atmospheric dust, with ice/snow accumulation perhaps controlling sedimentation along the wallrock. An examination of other regional hydrated deposits around southwestern Melas indicates similar draping deposits occur farther east and west along the wallrock, whereas layered sulfates to the southeast consist of monohydrated and polyhydrated sulfates that are similar to interior layered deposits found in many of the chasmata. Small opal

  18. Texture and depositional history of near-surface alluvial deposits in the central part of the western San Joaquin Valley, California

    USGS Publications Warehouse

    Laudon, Julie; Belitz, Kenneth

    1989-01-01

    Saline conditions and associated high levels of selenium and other soluble trace elements in soil, shallow ground water, and agricultural drain water of the western San Joaquin Valley, California, have prompted a study of the texture of near-surface alluvial deposits in the central part of the western valley. Texture is characterized by the percentage of coarse-grained sediment present within a specified subsurface depth interval and is used as a basis for mapping the upper 50 feet of deposits. Resulting quantitative descriptions of the deposits are used to interpret the late Quaternary history of the area. Three hydrogeologic units--Coast Range alluvium, flood-basin deposits, and Sierran sand--can be recognized in the upper 50 feet of deposits in the central part of the western San Joaquin Valley. The upper 30 feet of Coast Range alluvium and the adjacent 5 to 35 feet of flood-basin deposits are predominantly fine grained. These fine-grained Coast Range deposits are underlain by coarse-grained channel deposits. The fine-grained flood basin deposits are underlain by coarse-grained Sierran sand. The extent and orientation of channel deposits below 20 feet in the Coast Range alluvium indicate that streams draining the Coast Range may have been tributary to the axial stream that deposited the Sierran sand and that streamflow may have been to the southeast. The fining-upward stratigraphic sequence in the upper 50 feet of deposits and the headward retreat of tributary stream channels from the valley trough with time support a recent hypothesis of climatic control of alluviation in the western San Joaquin Valley.

  19. A new Burgess Shale-type deposit from the Ediacaran of western Mongolia

    PubMed Central

    Dornbos, Stephen Q.; Oji, Tatsuo; Kanayama, Akihiro; Gonchigdorj, Sersmaa

    2016-01-01

    Preservation of soft-bodied organisms is exceedingly rare in the fossil record. One way that such fossils are preserved is as carbonaceous compressions in fined-grained marine sedimentary rocks. These deposits of exceptional preservation are known as Burgess Shale-type (BST) deposits. During the Cambrian Period, BST deposits are more common and provide a crucial view of early animal evolution. The earliest definitive fossil evidence for macroscopic animal-grade organisms is found in the preceding Ediacaran Period. BST deposits from the Ediacaran are rarer and lack conclusive evidence for animals. Here we report the discovery of a new Ediacaran BST deposit with exceptional preservation of non-mineralizing macro-organisms in thinly bedded black shale from Zavkhan Province, western Mongolia. This fossil assemblage, here named the Zuun-Arts biota, currently consists of two new species of probable macroscopic multicellular benthic algae. One species, Chinggiskhaania bifurcata n. gen., n. sp., dominates the biota. The other species, Zuunartsphyton delicatum n. gen., n. sp., is known from three specimens. SEM-EDS analysis shows that the fossils are composed of aluminosilicate clay minerals and some carbon, a composition comparable to fossils from the Cambrian Burgess Shale biota. This discovery opens a new window through which to view late Precambrian life. PMID:26988136

  20. Geochemical discrimination of five pleistocene Lava-Dam outburst-flood deposits, western Grand Canyon, Arizona

    USGS Publications Warehouse

    Fenton, C.R.; Poreda, R.J.; Nash, B.P.; Webb, R.H.; Cerling, T.E.

    2004-01-01

    Pleistocene basaltic lava dams and outburst-flood deposits in the western Grand Canyon, Arizona, have been correlated by means of cosmogenic 3He (3Hec) ages and concentrations of SiO2, Na2O, K2O, and rare earth elements. These data indicate that basalt clasts and vitroclasts in a given outburst-flood deposit came from a common source, a lava dam. With these data, it is possible to distinguish individual dam-flood events and improve our understanding of the interrelations of volcanism and river processes. At least five lava dams on the Colorado River failed catastrophically between 100 and 525 ka; subsequent outburst floods emplaced basalt-rich deposits preserved on benches as high as 200 m above the current river and up to 53 km downstream of dam sites. Chemical data also distinguishes individual lava flows that were collectively mapped in the past as large long-lasting dam complexes. These chemical data, in combination with age constraints, increase our ability to correlate lava dams and outburst-flood deposits and increase our understanding of the longevity of lava dams. Bases of correlated lava dams and flood deposits approximate the elevation of the ancestral river during each flood event. Water surface profiles are reconstructed and can be used in future hydraulic models to estimate the magnitude of these large-scale floods.

  1. The boron isotope geochemistry of the neogene borate deposits of western Turkey

    NASA Astrophysics Data System (ADS)

    Palmer, M. R.; Helvaci, C.

    1997-08-01

    We have analyzed the boron isotope composition of 80 borate minerals (major minerals: borax, colemanite, and ulexite; minor minerals: veatchite-A, tunellite, kernite, terrugite, probertite, meyer-hofferite, inderite, inyoite, hydroboracite, howlite, and pandermite) from the main deposits (Kirka, Bigadiç, and Emet) and two smaller deposits (Kestelek and Sultançayir) in the western Turkish borate deposits. Forty-three samples were also analysed for their Sr isotope composition. The data span a wide range in δ11B values from -1.6%o to -25.3%o. The δ 11B values of the main borate minerals are largely controlled by their mineralogy and the pH of the brines from which they precipitated. An inverse correlation between the average δ 11B and 87Sr/86Sr ratios of colemanite in the different deposits suggests there is some variation in the sources of boron and Sr to the deposits. Emet has the highest contribution from aluminosilicates and Kirka the highest contribution from Eocene carbonates, with Bigadiç occupying an intermediate position. The δ11B values of the minor borate minerals distinguish between those which are primary precipitates from the original brines (or formed from primary borates without boron loss from the system) and those which formed from alteration of preexisting borate minerals with substantial loss of boron from the system.

  2. A new Burgess Shale-type deposit from the Ediacaran of western Mongolia

    NASA Astrophysics Data System (ADS)

    Dornbos, Stephen Q.; Oji, Tatsuo; Kanayama, Akihiro; Gonchigdorj, Sersmaa

    2016-03-01

    Preservation of soft-bodied organisms is exceedingly rare in the fossil record. One way that such fossils are preserved is as carbonaceous compressions in fined-grained marine sedimentary rocks. These deposits of exceptional preservation are known as Burgess Shale-type (BST) deposits. During the Cambrian Period, BST deposits are more common and provide a crucial view of early animal evolution. The earliest definitive fossil evidence for macroscopic animal-grade organisms is found in the preceding Ediacaran Period. BST deposits from the Ediacaran are rarer and lack conclusive evidence for animals. Here we report the discovery of a new Ediacaran BST deposit with exceptional preservation of non-mineralizing macro-organisms in thinly bedded black shale from Zavkhan Province, western Mongolia. This fossil assemblage, here named the Zuun-Arts biota, currently consists of two new species of probable macroscopic multicellular benthic algae. One species, Chinggiskhaania bifurcata n. gen., n. sp., dominates the biota. The other species, Zuunartsphyton delicatum n. gen., n. sp., is known from three specimens. SEM-EDS analysis shows that the fossils are composed of aluminosilicate clay minerals and some carbon, a composition comparable to fossils from the Cambrian Burgess Shale biota. This discovery opens a new window through which to view late Precambrian life.

  3. A new Burgess Shale-type deposit from the Ediacaran of western Mongolia.

    PubMed

    Dornbos, Stephen Q; Oji, Tatsuo; Kanayama, Akihiro; Gonchigdorj, Sersmaa

    2016-01-01

    Preservation of soft-bodied organisms is exceedingly rare in the fossil record. One way that such fossils are preserved is as carbonaceous compressions in fined-grained marine sedimentary rocks. These deposits of exceptional preservation are known as Burgess Shale-type (BST) deposits. During the Cambrian Period, BST deposits are more common and provide a crucial view of early animal evolution. The earliest definitive fossil evidence for macroscopic animal-grade organisms is found in the preceding Ediacaran Period. BST deposits from the Ediacaran are rarer and lack conclusive evidence for animals. Here we report the discovery of a new Ediacaran BST deposit with exceptional preservation of non-mineralizing macro-organisms in thinly bedded black shale from Zavkhan Province, western Mongolia. This fossil assemblage, here named the Zuun-Arts biota, currently consists of two new species of probable macroscopic multicellular benthic algae. One species, Chinggiskhaania bifurcata n. gen., n. sp., dominates the biota. The other species, Zuunartsphyton delicatum n. gen., n. sp., is known from three specimens. SEM-EDS analysis shows that the fossils are composed of aluminosilicate clay minerals and some carbon, a composition comparable to fossils from the Cambrian Burgess Shale biota. This discovery opens a new window through which to view late Precambrian life. PMID:26988136

  4. Structure and formation conditions of paleogene coal-bearing deposits of Western Kamchatka

    SciTech Connect

    Polyanskii, B.V.

    1995-03-01

    Peculiarities of lithofacial composition and cyclic structure of the Lower-Middle Paleogene volcano-terrigenous coal-bearing deposits of the Western Kamchatka marginal sedimentary basin are discussed. Unstable sedimentation under delta progradation environments is shown to be prevalent. Such conditions were favorable for coal formation of deltaic and alluvial-estuarine types. Against a background of the marine-coastal high rate (avalanche) sedimentation, short-lived conditions for dominantly allochthonous coal formation in the environment of humid, warm temperature climate and high changeable sedimentation rates were distinguished. The clastic material in the basin originates from two provenances, represented by Pre-Paleogene, mainly Cretaceous rocks. The Central Range supplied mainly coarse-grained graywacke material. The western continental denudation areas, consisting of sedimentary and igneous rocks (including granites), supplied fine-grained terrigenous graywacke-arkosic material.

  5. Geology and timing of mineralization at the Cangshang gold deposit, north-western Jiaodong Peninsula, China

    USGS Publications Warehouse

    Zhang, X.; Cawood, Peter A.; Wilde, S.A.; Liu, R.; Song, H.; Li, W.; Snee, L.W.

    2003-01-01

    The Cangshang gold deposit of the northwestern Jiaodong Peninsula contains reserves of greater than 50 tonnes (t) and is developed by the largest open pit gold mine in China. This deposit is a Jiaojia-style (i.e. disseminated-and-veinlet) deposit. It is controlled by the San-Cang fault zone, which trends ???040?? and dips 40-75??SE at the mine site. The main (no. 1) orebody lies between a hanging wall of Precambrian metamorphic rocks (mainly amphibolite) of the Fenzishan Group and a footwall composed of the Mesozoic Linglong granitoid. The ore zone is mainly composed of pyritized, sericitized and silicified granitoid, which has undergone variable degrees of cataclasis. SHRIMP U-Pb dating of zircon indicates that the protolith of the hanging wall amphibolite was formed at 2530 ?? 17 Ma and underwent metamorphism at 1852 ?? 37 Ma. The footwall granodiorite has been dated at 166 ?? 4 Ma, whereas zircons from the ore zone yield a younger age of 154 ?? 5 Ma. Cathodoluminescence images of zircons from the granodiorite and ore zone show oscillatory zonation indicative of an igneous origin for both and the ages of these zircons, therefore, are all interpreted to be representative of magmatic crystallization. Dating of sericite by 40Ar-39Ar has been used to directly determine the timing of formation of the Cangshang deposit, providing the first time absolute age on formation of the Jiaojia-style gold deposits. The well-defined age of 121.3 ?? 0.2 Ma provides the precise timing of gold mineralization at the Cangshang deposit. This age is consistent with those of Linglong-style (vein type) gold mineralization, also from the north-western Jiaodong Peninsula, at between 126 and 120 Ma. Therefore, our work indicates that both styles of gold deposits in the Jiaodong Peninsula were formed during the same mineralization event.

  6. Clasts petrography of post-glacial deposits in the Lubusz Elevation, western Poland

    NASA Astrophysics Data System (ADS)

    Lipka, Ewelina

    2010-05-01

    Clasts petrography of post-glacial deposits in the Lubusz Elevation, western Poland Ewelina Lipka Department of Geomorphology, Adam Mickiewicz University, Poznan, Poland This study presents petrographic composition of post-glacial deposits in the Lubusz Elevation. Also parent areas and possible general ice-flow directions of those deposits were determined on the basis of clasts petrography. This contribution concerns the Lubusz Elevation, located in western Poland. This area is situated within the range of the Poznan Phase, which is the second stage of the Weichselian Ice Sheet in Poland. The author aimed at revealing a spatial tendency in petrographic composition of post-glacial deposits that comprise the Poznan Phase marginal zone. This petrographic composition became also a basis to determine parent areas and possible general ice-flow directions of the analysed deposits. The data set was collected from post-glacial deposits of varied lithology (superficial glacial till and glaciofluvial deposits) across the Poznan Phase marginal zone (end moraine, hinterland and foreland). Gravels of 4-10 and 20-60 mm fractions of both glacial till and glaciofluvial deposits were petrographically analysed. Also indicator and statistical erratics were recognised within the 20-60 mm fraction. All analysed deposits, disregarding either place of their occurance (end moraine, hinterland or foreland) or lithology (glacial till or glaciofluvial deposits) were found to consist mainly of crystalline rocks. Among end moraine and hinterland deposits (apart from crystalline rocks) Palaeosoic limestones, Palaeosoic sandstones and flints are present in significant amounts. Foreland deposits consist mainly (beside crystalline rocks) of Palaeosoic sandstones and flints. More Palaeosoic sandstones and flints and less quartz grains were observed among 20-60 mm fraction gravels comparing to those of 4-10 mm fraction. Significant percentage of flints in all analysed samples was found remarkable. It

  7. Middle to Late Pleistocene coastal deposits of Eivissa (Western Mediterranean): Chronology and evolution.

    NASA Astrophysics Data System (ADS)

    Del Valle, Laura; Pomar, Francisco; Fornós, Joan J.; Gómez-Pujol, Lluís; Anechitei-Deacu, Valentina; Timar-Gabor, Alida

    2016-04-01

    This study deals with the sedimentary and stratigraphical description of Pleistocene deposits from seven coastal areas of Eivissa (Balearic Islands). Twenty two sedimentary facies have been described involving the succession of eolian, colluvial and edaphic environments. Carbonate sandstones, breccias and silty deposits are the main component of these sequences. Despite the extensive eolian systems outcropping along the coast of Eivissa, there are very few studies performed to chronological framework of these deposits. Luminescence measurements were carried out using an automated RisØ TL/OSL-DA-20 reader in the Luminescence Dating Laboratory of Babes-Bolyai University (Cluj-Napoca, Romania) under low intensity red light. OSL dating of nineteen eolian levels indicate that their deposition took place between the Middle and Late Pleistocene, establishing a paleoclimatic evolution of Eivissa Island since 755 ka to 70 Ka. Eolian activity in the Eivissa Island can be correlated with regression episodes which took place during cold periods associated with different isotopic stages, concretely the MIS 18, 16, 12, 10, 8, 6 and 4. Similar results have been obtained from many sites along the western Mediterranean Sea such as Mallorca (Pomar i Cuerda, 1979; Nielsen et al, 2004; Fornós et al, 2009), Sardinia (Andreucci et al, 2009; Pascucci et al, 2014), Liguria (Pappalardo et al., 2013). Keywords: Eolian dunes, Pleistocene, Climatic evolution, Eivissa. References - Andreucci, S.; Pascucci, V.; Murray, A. S.; Clemmensen, L. B. 2009. Late Pleistocene coastal evolution of San Giovanni di Sinis, west Sardinia (Western Mediterranean). Sedimentary Geology, 216: 104- 116 - Fornós, J.J.; Clemmensen, L.B.; Gómez-Pujol, L.; Murray, A. 2009. Late Pleistocene carbonate aeolianites on Mallorca, Western Mediterranean: a luminescence chronology. Quaternary Science reviews 28: 2697-2709. -Nielsen, K.A.; Clemmensen, L.B.; Fornós, J.J. 2004. Middle Pleistocene magnetostratigraphy and

  8. Methane in ground ice and frozen Quaternary deposits of Western Yamal

    NASA Astrophysics Data System (ADS)

    Vasiliev, A. A.; Streletskaya, I. D.; Melnikov, V. P.; Oblogov, G. E.

    2015-12-01

    The content and the genesis of methane in underground ice and frozen Quaternary sediments of Western Yamal is studied. The minimum concentration of methane in frozen Quaternary deposits was found for sand: 15-100 ppm V. The maximum concentration of methane reaches 3000 ppm V in marine clays. The concentration of methane in the ice wedges is 100-700 ppm V, and in the massive ground ice can be more than 10 000 ppm V. The high content of methane in the massive ground ice we explain by migration of methane from freezing deposits into ice body during its formation. The close connection between methane concentration and organic carbon content is found.

  9. Depositional sequences in a foreland basin (north-western domain of the continental Duero basin, Spain)

    NASA Astrophysics Data System (ADS)

    Herrero, Antonio; Alonso-Gavilán, Gaspar; Colmenero, Juan Ramón

    2010-01-01

    The Cenozoic record of the north-western domain of the Duero basin is articulated at the surface through a set of continental depositional sequences called, from base to top, the Vegaquemada sequence, the Candanedo sequence, and the Barrillos sequence. These depositional sequences were deposited in continental sedimentary environments. The deposition of the first sequence occurred through a fluvial system with floodplains cut by low-sinuosity channels. The Vegaquemada sequence was developed between the Middle Eocene and the Early Agenian. The second sequence was formed by a set of highly efficient transport alluvial fans that evolved laterally towards fluvial systems with low-sinuosity fluvial channels and an extensive floodplain, where several types of palaeosols were formed. This sequence developed between the Early Agenian and the Late Vallesian. The third unit-the Barrillos sequence (between the Late Vallesian and the Turolian/Ruscinian transition), was generated by a set of highly efficient transport alluvial fans dominated by low-sinuosity fluvial channels. In subsurface geology, seismic and well data are used to rebuild the stratigraphic architecture. The two basal depositional sequences can be identified with two seismic units: the Palaeogene Seismic Unit (PgSU) and the Neogene Seismic Unit (NgSU), respectively. In the present work, we obtained the isovelocity, isochron, and isobath maps for the top and base of the two Cenozoic units. The Palaeozoic (PzSU) and Mesozoic (MzSU) seismic units are found under these two units. Through study of the logs of the various boreholes, it was only possible to analyse the upper 700 m of the Candanedo Sequence (NgSU), without encompassing the total thickness of the unit. Several middle-order sequences were differentiated, in general showing a sequential fining-upwards evolutionary character. Additionally, for the boreholes analysed two main types of electrofacies were identified, both representing fluvial channels and

  10. Geological and geophysical characteristics of massive sulphide deposits: A case study of the Lirhanda massive sulphide deposit of Western Kenya

    NASA Astrophysics Data System (ADS)

    Dindi, E.; Maneno, J. B. J.

    2016-08-01

    An integrated geophysical ground survey was conducted on an airborne electromagnetic (EM) anomaly located in Kakamega forest of Western Kenya. The purpose of the study was to establish the existence of massive sulphides and identify suitable optimal geophysical method(s) for the investigation of similar anomalies. The study was also expected to provide information on the geological and geophysical characteristics of the deposit. Field work involved electromagnetic methods: Vertical Loop (VLEM), Horizontal Loop (HLEM), TURAM EM and potential field methods: gravity and magnetics. Geochemical sampling was carried out concurrently with the geophysical survey. All the geophysical methods used yielded good responses. Several conductors conforming to the strike of the geology were identified. TURAM EM provided a higher resolution of the conductors compared to VLEM and HLEM. The conductors were found to be associated with positive gravity anomalies supporting the presence of bodies of higher density than the horst rock. Only the western section (west of 625W) of the grid is associated with strong magnetic anomalies. East of 625W strong EM and gravity anomalies persist but magnetic anomalies are weak. This may reflect variation in the mineral composition of the conductors from magnetic to non-magnetic. Geochemical data indicates strong copper anomalies (upto 300 ppm) over sections of the grid and relatively strong zinc (upto 200 ppm) and lead (upto 100 ppm) anomalies. There is a positive correlation between the location of the conductors as predicted by TURAM EM and the copper and zinc anomalies. A test drill hole proposed on the basis of the geophysical results of this study struck massive sulphides at a depth of 30m still within the weathered rock zone. Unfortunately, the drilling was stopped before the sulphides could be penetrated. The drill core revealed massive sulphide rich in pyrite and pyrrhotite. An attempt has been made to compare characteristics of the

  11. Chapter F: Preliminary Bibliography of Lacustrine Diatomite Deposits in the Western United States and Related Topics

    USGS Publications Warehouse

    Bolm, Karen S.; Wallace, Alan R.; Moyle, Phillip R.; Bliss, James D.; Orris, Greta J.

    2003-01-01

    Introduction As part of the assessment of lacustrine diatomite resources in the Western United States (fig. 1), U.S. Geological Survey (USGS) project members conducted a review of literature relating to the formation, location, and nature of deposits in the study area. This preliminary bibliography consists of selected publications to identify, locate, and describe the deposits to be studied, to characterize common geologic factors about the deposits, and to better understand the factors that control their formation, preservation, or destruction. The bibliography also serves as a resource for other workers to research the topic. References included in the preliminary bibliography were gathered by searching existing bibliographic data bases and library collections. Project researchers also contributed references that they found during the course of their work. This bibliography should be considered a working document that will grow as research and literature searches continue. Clearly, many significant publications may be missing from this preliminary list; therefore, USGS staff members intend to issue a revised bibliography as project work progresses. To assure completeness, input from other researchers and industry is welcome. Although the focus of this bibliography is lacustrine diatomite deposits of the Western United States, additional references that provide a foundation of knowledge for the study of diatomites, diatoms, and diatom-related processes (ecology, geology, geochemistry) and for the uses and behavior of diatomite have also been included. An index of keywords has been added to this bibliography, designed to help the user locate reports by topic or by geographic location. The letter 'A' following a number indicates that the report referenced is an abstract.

  12. A characterisation of the coastal tufa deposits of south-west Western Australia

    NASA Astrophysics Data System (ADS)

    Forbes, Matt; Vogwill, Ryan; Onton, Kimberly

    2010-12-01

    Located in the south-west coastal zone of Western Australia are numerous tufa deposits, which are registered as Threatened Ecological Communities (TEC). The tufas occur in near-shore shallow bedrock settings and are associated with local groundwater discharge. Depositional facies, mineralogy, elemental chemistry and water quality were investigated for five key deposits. Two conceptual environmental models are identified. The first, the cascade to barrage pool model is associated with coastal waterfall zones, the second, a perched spring-line and barrage pool model is located predominantly in the supratidal zone. Tufa morphology, texture, mineral composition and elemental chemistry vary within and between sites. Both phytoclast and lithoclast (allochthonous), and phytoherm forms of tufa are identified depending on location within the facies. Calcite, and to a lesser extent, aragonite and Mg-calcite dominate tufa mineralogy, with diagenetic modifications apparent. Tufa water chemistry is generally Na-Cl-HCO 3 dominated; however, Na-Cl concentrations increase at sites situated within the supratidal zone. Currently the most likely potential threat posed to these deposits is increasing nutrient levels in spring waters from agricultural land use within the catchments. This could in the future impact on tufa development.

  13. Distribution and sedimentary characteristics of tsunami deposits along the Cascadia margin of western North America

    USGS Publications Warehouse

    Peters, R.; Jaffe, B.; Gelfenbaum, G.

    2007-01-01

    Tsunami deposits have been found at more than 60 sites along the Cascadia margin of Western North America, and here we review and synthesize their distribution and sedimentary characteristics based on the published record. Cascadia tsunami deposits are best preserved, and most easily identified, in low-energy coastal environments such as tidal marshes, back-barrier marshes and coastal lakes where they occur as anomalous layers of sand within peat and mud. They extend up to a kilometer inland in open coastal settings and several kilometers up river valleys. They are distinguished from other sediments by a combination of sedimentary character and stratigraphic context. Recurrence intervals range from 300-1000??years with an average of 500-600??years. The tsunami deposits have been used to help evaluate and mitigate tsunami hazards in Cascadia. They show that the Cascadia subduction zone is prone to great earthquakes that generate large tsunamis. The inclusion of tsunami deposits on inundation maps, used in conjunction with results from inundation models, allows a more accurate assessment of areas subject to tsunami inundation. The application of sediment transport models can help estimate tsunami flow velocity and wave height, parameters which are necessary to help establish evacuation routes and plan development in tsunami prone areas. ?? 2007.

  14. Emission, Dispersion, Transformation, and Deposition of Asian Particulates Over the Western Pacific Ocean

    SciTech Connect

    Turco, Richard P.

    2005-02-28

    In this project we developed and applied a coupled three-dimensional meteorology/chemistry/microphysics model to study the patterns of aerosol dispersion and deposition in the western Pacific area; carried out a series of detailed regional aerosol simulations to test the ability of models to treat emission, dispersion and removal processes prior to long-range transport; calculated and analyzed trajectories that originate in Asian dust source regions and reach the Pacific Basin; performed detailed simulations of regional and trans-Pacific transport, as well as the microphysical and chemical properties, of aerosols in the Asia-Pacific region to quantify processes that control the emission, dispersion and removal of particles; and assessed the contributions of regional-scale Asian particulate sources to the deposition of pollutants onto surface waters. The transport and deposition of aerosols and vapors were found to be strongly controlled by large and synoptic scale meteorology, convection, turbulence, and precipitation, as well as strong interactions between surface conditions and topographical features. The present analysis suggests that accurate representations of aerosol sources, transport and deposition can be obtained using a comprehensive modeling approach.

  15. Slope depositional processes along western Great Bahama Bank: A rapidly prograding carbonate platform

    SciTech Connect

    Wilber, R.J. ); Halley, R.B. ); Milliman, J.D. )

    1991-03-01

    The western margin of Great Bahama Bank has prograded rapidly into the Santaren Channel throughout Quaternary time. Platform growth is accomplished mainly by vigorous outbuilding of the slope - up to 500 m in the last 6-10 ka. Seismic stratigraphy and sediment and rock analysis reveal sharp contrasts in depositional facies and mechanisms of growth between the upper slope (50-160 m) and lower slope (160-600 m). The upper slope is steep (30-60{degree}) and rock with a thin (< 1 m) layer of coarse Halimeda sand. In situ sediment production, in combination with cementation by magnesium clacite, allows this interval to grow as a slowly accreting (meters/1,000 yr), lithified surface. Because of cementation, slope failure is rare but, in some areas, large blocks calved off the upper slope are found on the lower slope (mega-breccia). The lower slope is gentle (10-30{degree}) and consists of thick (up to 90 m) accumulations of fine bank-top sediment. Deposition occurs episodically via settling of sediment plumes swept off the bank during large storms. Lower slope deposits are absent where off-bank transport is barred by shelf-edge islands. In addition, hyperpycnal flows which cascade over the margin both sweep the upper slope and erode lower slope deposits near the depth of onlap. Slope failure in the uncemented lower slope deposits is primarily via slumping and possibly gravity flows. Lower slope deposition occurs only during sea level high stands when the rates of growth may be an order of magnitude higher than those of the upper slope which apparently experiences slow growth throughout most of a sea level cycle.

  16. A multi-proxy palaeoecological and palaeoclimatic record within full glacial lacustrine deposits, western Tennessee, USA

    USGS Publications Warehouse

    Grimley, D.A.; Daniel, L.; Kaplan, S.W.; Yansa, C.H.; Curry, B. Brandon; Oches, E.A.

    2009-01-01

    The Fulton Section, along the Mississippi River in western Tennessee, USA, is a 1km continuous exposure (~20m vertically) of Quaternary fluvial and lacustrine deposits, inset within Eocene sediments and buried by thick loess. Fossiliferous slackwater lake sediments record maximum aggradation during the last two major glaciations, with deposition between ca. 190-140 ka and 24-1814C ka BP, based on amino acid and radiocarbon chronology, respectively. During the onset of full glacial conditions (ca. 24-22 14C ka BP), a relatively permanent shallow lake environment is indicated by ostracods, aquatic molluscs, and both pollen and macrofossils of aquatic plants. By 21.8 14C ka BP, increasing emergent plants, amphibious gastropods (Pomatiopsis) and heavier ??18O compositions suggest marsh-like conditions in a periodically drying lake. The surrounding uplands consisted of Picea-Pinus woodlands mixed with cool-temperate hardwoods (e.g. Quercus, Populus, Carya), grasses and herbs. More open conditions ensued ca. 20 14C ka BP, with loess and slopewash gradually infilling the former lake by 18 14C ka BP. Modern analogue analyses of ostracods and palaeontological evidence imply a full glacial climate similar to today's mixed-boreal zone in central Minnesota, USA, about 98C cooler in mean annual temperature than present-day western Tennessee. Copyright ?? 2009 John Wiley & Sons, Ltd.

  17. Geometry of the neoproterozoic and paleozoic rift margin of western Laurentia: Implications for mineral deposit settings

    USGS Publications Warehouse

    Lund, K.

    2008-01-01

    The U.S. and Canadian Cordilleran miogeocline evolved during several phases of Cryogenian-Devonian intracontinental rifting that formed the western mangin of Laurentia. Recent field and dating studies across central Idaho and northern Nevada result in identification of two segments of the rift margin. Resulting interpretations of rift geometry in the northern U.S. Cordillera are compatible with interpretations of northwest- striking asymmetric extensional segments subdivided by northeast-striking transform and transfer segments. The new interpretation permits integration of miogeoclinal segments along the length of the western North American Cordillera. For the U.S. Cordillera, miogeoclinal segments include the St. Mary-Moyie transform, eastern Washington- eastern Idaho upper-plate margin, Snake River transfer, Nevada-Utah lower-plate margin, and Mina transfer. The rift is orthogonal to most older basement domains, but the location of the transform-transfer zones suggests control of them by basement domain boundaries. The zigzag geometry of reentrants and promontories along the rift is paralleled by salients and recesses in younger thrust belts and by segmentation of younger extensional domains. Likewise, transform transfer zones localized subsequent transcurrent structures and igneous activity. Sediment-hosted mineral deposits trace the same zigzag geometry along the margin. Sedimentary exhalative (sedex) Zn-Pb-Ag ??Au and barite mineral deposits formed in continental-slope rocks during the Late Devonian-Mississippian and to a lesser degree, during the Cambrian-Early Ordovician. Such deposits formed during episodes of renewed extension along miogeoclinal segments. Carbonate-hosted Mississippi Valley- type (MVT) Zn-Pb deposits formed in structurally reactivated continental shelf rocks during the Late Devonian-Mississippian and Mesozoic due to reactivation of preexisting structures. The distribution and abundance of sedex and MVT deposits are controlled by the

  18. Sichuan Earthquake in China

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Sichuan earthquake in China occurred on May 12, 2008, along faults within the mountains, but near and almost parallel the mountain front, northwest of the city of Chengdu. This major quake caused immediate and severe damage to many villages and cities in the area. Aftershocks pose a continuing danger, but another continuing hazard is the widespread occurrence of landslides that have formed new natural dams and consequently new lakes. These lakes are submerging roads and flooding previously developed lands. But an even greater concern is the possible rapid release of water as the lakes eventually overflow the new dams. The dams are generally composed of disintegrated rock debris that may easily erode, leading to greater release of water, which may then cause faster erosion and an even greater release of water. This possible 'positive feedback' between increasing erosion and increasing water release could result in catastrophic debris flows and/or flooding. The danger is well known to the Chinese earthquake response teams, which have been building spillways over some of the new natural dams.

    This ASTER image, acquired on June 1, 2008, shows two of the new large landslide dams and lakes upstream from the town of Chi-Kua-Kan at 32o12'N latitude and 104o50'E longitude. Vegetation is green, water is blue, and soil is grayish brown in this enhanced color view. New landslides appear bright off-white. The northern (top) lake is upstream from the southern lake. Close inspection shows a series of much smaller lakes in an elongated 'S' pattern along the original stream path. Note especially the large landslides that created the dams. Some other landslides in this area, such as the large one in the northeast corner of the image, occur only on the mountain slopes, so do not block streams, and do not form lakes.

  19. North-Atlantic millennial-timescale variability imprint on Western European loess deposits: a modeling study

    NASA Astrophysics Data System (ADS)

    Sima, A.; Rousseau, D.; Kageyama, M.; Ramstein, G.; Schulz, M.; Balkanski, Y.; Antoine, P.; Dulac, F.; Hatte, C.

    2008-12-01

    We test if the dust cycle response to the North-Atlantic abrupt climate changes, the Dansgaard-Oeschger (DO) and Heinrich (H) events, could have led to the recording of these events in the Western European loess deposits. The LMDZ AGCM is used to simulate a reference glacial state "DOS", assimilated to a DO stadial, a cold perturbation "HE", resembling a H event, and a warm perturbation "DOI", assimilated to a DO interstadial. The reference state corresponds to the 40-kyr BP context, in the middle of the typical glacial period (75-15 kyr BP). The two perturbations are obtained by applying cold, respectively warm anomalies of up to 2°C to the North-Atlantic surface temperatures in the latitudinal band 30°- 63°N. The simulated climates are compared from the point of view of dust emission, with a focus on the English Channel and the south of the North Sea (ECSNS), important dust sources for the Western European loess deposits. When only considering the changes in wind, precipitation, soil moisture and snow cover over the ECSNS and loess deposit areas, the differences of dust emission flux between the simulations are small, in contradiction with the observed stadial-interstadial loess sedimentation rate variations. However, when including the vegetation effect of inhibiting the eolian erosion, the three climates are clearly differentiated, the dust flux for DOI becoming less than half of that for DOS and HE. This shows that vegetation changes have played a key role in the stadial-interstadial dust cycle variations.

  20. Large-scale Crustal Features, Epithermal Gold Deposits, and the Yellowstone Hotspot, Western U.S.

    NASA Astrophysics Data System (ADS)

    Ponce, D. A.; Glen, J. M.

    2001-12-01

    Aeromagnetic and filtered magnetic maps of the western U.S. reveal at least 3 and up to 6 narrow, arcuate anomalies that form a radial pattern, the geometry of which suggests a unifying process. The most notable of these anomalies is the northern Nevada rift (NNRe), first identified as a high-amplitude, linear aeromagnetic anomaly extending from the Nevada-Oregon boarder for several hundred kilometers to the south-southeast. The NNRe anomaly is associated with a mid-Miocene mafic dike swarm, presumably emplaced along a narrow rift corridor and represents the mid-Miocene stress direction (Zoback, 1978; Zoback and others, 1994). Other similar, though less prominent geophysical anomalies occur to the west of the NNRe. With the aid of filtering and gradient analysis these anomalies, along with the NNRe appear to extend northward into Oregon and verge towards a common point. Numerous other geologic lineations, when extrapolated intersect at virtually the same location, suggesting that all these features radiate from a single point located along the Idaho-Oregon boarder at lat 44 oN (Glen and Ponce, 2000). A possible explanation for this pattern is a point stress at the base of the lithosphere related to the impact of the Yellowstone hotspot. Because the northern Nevada rift has been shown to correlate with mid-Miocene epithermal gold deposits along its trend (John and Wallace, 2000; John and others, 2000), we investigate the association of epithermal gold deposits to other similar arcuate features in northern Nevada. Mid-Miocene and younger epithermal gold-silver deposits also occur along two prominent aeromagnetic anomalies west of the northern Nevada rift and to three less prominent arcuate magnetic features. We speculate that mid-Miocene epithermal deposits formed along deep fractures associated with mid-Miocene rift-related magmatism, ultimately related to the inception of the Yellowstone hotspot, and that younger deposits preferentially followed these pre

  1. Geological characteristics and ore-forming process of the gold deposits in the western Qinling region, China

    NASA Astrophysics Data System (ADS)

    Liu, Jiajun; Liu, Chonghao; Carranza, Emmanuel John M.; Li, Yujie; Mao, Zhihao; Wang, Jianping; Wang, Yinhong; Zhang, Jing; Zhai, Degao; Zhang, Huafeng; Shan, Liang; Zhu, Laimin; Lu, Rukui

    2015-05-01

    The western Qinling, belonging to the western part of the Qinling-Dabie-Sulu orogen between the North China Block and South China Block, is one of the most important gold regions in China. Isotopic dates suggest that the Mesozoic granitoids in the western Qinling region emplaced during the Middle-Late Triassic, and the deposits formed during the Late Triassic. Almost all gold deposits in the western Qinling region are classified as orogenic, Carlin-type, and Carlin-like gold deposits, and they are the products of Qinling Orogenesis caused by the final collision between the North China Block and the South China Block. The early subduction of the Mian-Lue oceanic crust and the latter collision between South Qinling Terrane and the South China Block along the Mian-Lue suture generated lithosphere-scale thermal anomalies to drive orogen-scale hydrothermal systems. The collision-related magmatism also provided heat source for regional ore-forming fluids in the Carlin-like gold deposits. Orogenic gold deposits such as Huachanggou, Liziyuan, and Baguamiao lie between the Shang-Dan and Mian-Lue sutures and are confined to WNW-trending brittle-ductile shear zones in Devonian and Carboniferous greenschist-facies metasedimentary rocks that were highly-deformed and regionally-metamorphosed. These deposits are typical orogenic gold deposits and formed within a Late Triassic age. The deposits show a close relationship between Au and Ag. Ores contain mainly microscopic gold, and minor electrum and visible gold, along with pyrite. The ore-forming fluids were main metamorphic fluids. Intensive tectonic movements caused by orogenesis created fluid-migrating channels for precipitation locations. Although some orogenic gold deposits occur adjacent to granitoids, mineralization is not synchronous with magmatism; that is, the granitoids have no genetic relations to orogenic gold deposits. As ore-forming fluids converged into dilated fractures during the extension stage of orogenesis

  2. Modeling study of North-Atlantic millennial-timescale variability imprint on Western European loess deposits

    NASA Astrophysics Data System (ADS)

    Sima, A.; Rousseau, D.-D.; Kageyama, M.; Ramstein, G.; Schultz, M.; Balkanski, Y.; Antoine, P.; Dulac, F.; Hatté, C.

    2009-04-01

    Studies on loess sequences of Western Europe have shown (i) that the loess sedimentation pattern over the last glaciation (approximately 100 to 15 thousand years before present (kyr BP)) has been very similar throughout the European loess belt, indicating a common climate control, and (ii) that the rapid environmental changes on the continent are correlated with the North-Atlantic millennial-timescale variations, the so-called Dansgaard-Oeschger (DO) and Heinrich (H) events. Here we test, by means of numerical modelling, if, and by which mechanisms, the dust cycle response to the environmental changes induced by the DO and H events could have led to the recording of these events in the loess deposits of the Western Europe. The LMDZ atmosphere general circulation model, in a version with a stretched grid enhancing the resolution over Western Europe to 60km, is used to simulate (a) a reference glacial state, assimilated to a DO stadial (DOS), (b) a cold perturbation over the North Atlantic, resembling a H event, and (c) a warm perturbation, assimilated to a DO interstadial (DOI). The reference state corresponds to the 40-kyr BP context, in the middle of the typical glacial period (approximately 75 to 15 kyr BP). The subsequent perturbations are obtained by applying cold or warm anomalies of up to 2°C in absolute value to the North-Atlantic sea-surface temperatures in the latitudinal band 30° - 63°N. The three simulated climate states are compared from the point of view of the initial driver of the dust cycle, the dust emission. A detailed analysis is provided for the English Channel and the south of the North Sea (ECSNS), important deflation areas in glacial times, and a source for the Western European loess deposits. In our experiments, the impact of altering the North-Atlantic surface conditions is weak over the ECSNS and loess areas (roughly, the latitudinal band 48° - 53°N) with respect to wind and precipitation. When only considering these factors, and the

  3. Supratidal beach deposits in Giralia Bay (Exmouth Gulf, Western Australia) - a record for past tropical cyclones?

    NASA Astrophysics Data System (ADS)

    May, Simon Matthias; Gelhausen, Henrik; Brill, Dominik; Callow, Nik; Engel, Max; Scheffers, Anja; Joannes-Boyau, Renaud; Leopold, Matthias; Opitz, Stephan; Brückner, Helmut

    2016-04-01

    Past coastal flooding events related to tropical cyclones (TCs) and tsunamis may be inferred from geomorphic and sedimentary archives, i.e. in the form of particular landforms (beach ridges, washover fans), deposits (washover sediments in lagoons) or erosional features. In Giralia Bay, southern Exmouth Gulf (Western Australia), sandy ridge sequences in supratidal elevations form the landward margin of extensive mudflats. The formation of these ridges, as in other mudflats of NW Australia, is assumed to be mainly driven by TCs, although their relation to depositional processes and inundation levels during spring tide conditions, exceptional precipitation and discharge events, and storm surges needs to be clarified. Based on a simple process monitoring setup using a time-lapse camera and pressure gauges, geomorphological mapping by means of unmanned aerial vehicle survey and structure-from-motion techniques, as well as sedimentological and geochronological investigations, this study aims at (i) establishing the chronostratigraphy and reconstructing the formation of the supratidal beach deposits; (ii) identifying the most important driving processes involved in their formation; and (iii) understanding their significance for recording past TC activity. Sediment trenches cross the youngest, most seaward part of the ridge sequence. At the base of the sedimentary succession, sandy units are interbedded with mud layers, reflecting depositional conditions similar to the present distal mudflat. In the upper part of the ridges, mud intercalations recede, and sand layers of varying grain size distribution and mineralogical content dominate. Younger sediment layers clearly attach to older ones documenting the stepwise accretion of the ridges onto the mudflat. Muddy intercalations in the upper part of the succession are interpreted to represent deposition in locally restricted swales. Monitoring covered the time period between August 2013 and 2015 and capture an exceptional

  4. Triassic and Jurassic-Cretaceous deposits in the Western Chukotka: geodynamic implications, provenance studies and deformation

    NASA Astrophysics Data System (ADS)

    Tuchkova, M.

    2012-04-01

    Studied region is situated in western Chukotka, in Northeast Russia. We examine the part of Chukotka microplate, the key element in the evolution of the Amerasian basin. The Triassic of Chukotka is represented by up to 5 km of deposits. Triassic terrigeneous deposits consist of three different complexes: Lower-Middle Triassic, Upper Triassic Carnian, and Norian. All the complexes are represented by rhythmic intercalation of sandstones, siltstones and mudstones. Clastic material was carried by large rivers, possessing large reservoir on neighbouring continent. Progradation of delta system in deeper regions is observed. During the Triassic, sedimentation was represented by continental slope progradation. Petrographic study of mineral composition has established the sandstones as graywackes and lithic arenites, according to Pettijohn classification (1981). Sandstones with clasts of rock fragments of lower metamorphic grade rocks dominate at the base of Triassic deposits, sandstones with fragments of higher grade metamorphic rocks dominate in the Later Triassic deposits. This different shows that the Triassic represents an unroofing sequence sours of erosional processes that produced the clastic material eroded more deeply buried rocks through time. Detrital zircons from Triassic sedimentary rocks were collected for constain its paleogeographic links to source terranes. Zircons populations from these three samples are very similar, and youngest zircon ages show peaks at 236-255 Ma. Besides, we are dating the 9 samples for K-Ar and Rb-Sr methods. Data are similar and show 200-204 Ma, and we suppose that this isotopic data indicate the age of first stage of deformation in Chukotka's basin. The Jurassic-Cretaceous of Chukotka is represented by up to 3 km of deposits. The sedimentary complexes are enriched by organic matter, and fresh clastic materials. Fragments of shales, sometimes laminated or cleaved are their indicator constituents. Sandstones are arkosic. The

  5. A mid-Holocene candidate tsunami deposit from the NW Cape (Western Australia)

    NASA Astrophysics Data System (ADS)

    May, Simon Matthias; Falvard, Simon; Norpoth, Maike; Pint, Anna; Brill, Dominik; Engel, Max; Scheffers, Anja; Dierick, Manuel; Paris, Raphaël; Squire, Peter; Brückner, Helmut

    2016-03-01

    Although extreme-wave events are frequent along the northwestern coast of Western Australia and tsunamis in 1994 and 2006 induced considerable coastal flooding locally, robust stratigraphical evidence of prehistoric tropical cyclones and tsunamis from this area is lacking. Based on the analyses of X-ray computed microtomography (μCT) of oriented sediment cores, multi-proxy sediment and microfaunal analyses, optically stimulated luminescence (OSL) and 14C-AMS dating, this study presents detailed investigations on an allochthonous sand layer of marine origin found in a back-barrier depression on the NW Cape Range peninsula. The event layer consists of material from the adjacent beach and dune, fines and thins inland, and was traced up to ~ 400 m onshore. Although a cyclone-induced origin cannot entirely be ruled out, the particular architecture and fabric of the sediment, rip-up clasts and three subunits point to deposition by a tsunami. As such, it represents the first stratigraphical evidence of a prehistoric, mid-Holocene tsunami in NW Western Australia. It was OSL-dated to 5400-4300 years ago, thus postdating the regional mid-Holocene sea-level highstand.

  6. Increasing eolian dust deposition in the western United States linked to human activity

    NASA Astrophysics Data System (ADS)

    Neff, J. C.; Ballantyne, A. P.; Farmer, G. L.; Mahowald, N. M.; Conroy, J. L.; Landry, C. C.; Overpeck, J. T.; Painter, T. H.; Lawrence, C. R.; Reynolds, R. L.

    2008-03-01

    Mineral aerosols from dust are an important influence on climate and on marine and terrestrial biogeochemical cycles. These aerosols are generated from wind erosion of surface soils. The amount of dust emission can therefore be affected by human activities that alter surface sediments. However, changes in regional- and global-scale dust fluxes following the rapid expansion of human populations and settlements over the past two centuries are not well understood. Here we determine the accumulation rates and geochemical properties of alpine lake sediments from the western interior United States for the past 5,000 years. We find that dust load levels increased by 500% above the late Holocene average following the increased western settlement of the United States during the nineteenth century. We suggest that the increased dust deposition is caused by the expansion of livestock grazing in the early twentieth century. The larger dust flux, which persists into the early twenty-first century, results in a more than fivefold increase in inputs of K, Mg, Ca, N and P to the alpine ecosystems, with implications for surface-water alkalinity, aquatic productivity and terrestrial nutrient cycling.

  7. Spectral Mapping of Interior Layered Deposits of Western Candor Chasma by CRISM

    NASA Astrophysics Data System (ADS)

    Murchie, S.; Roach, L.; Milliken, R.; Seelos, F.; Wiseman, S.; Humm, D.; Mustard, J.; Bibring, J.; CRISM Team

    2007-12-01

    Western Candor Chasma contains a 3 km-thick sequence of interior layered deposits (ILDs) that may have been emplaced by sedimentary deposition subsequent to formation of Valles Marineris. Proposed genetic mechanisms include subaerial fluvial deposition or volcanism, accumulation of airfall dust, lacustrine evaporite precipitation, hydrovolcanism, or alternatively deep erosion of the chasma wall materials. Observations by the Mars Express/OMEGA spectrometer showed that the ILDs contain both monohydrated and polyhydrated sulfates in close spatial association with fine-grained ferric oxides having distinctive visible-infrared absorptions (Gendrin et al. 2005a,b). In general, OMEGA data also suggest that monohydrated sulfates are associated with steeper slopes and higher albedos than are polyhydrated sulfates (Mangold 2006). CRISM has observed the ILDs in western Candor using both its 200 m/pixel global mapping mode and targeted observations at 20 or 40 m/pixel. CRISM data show spatial heterogeneity in spectral properties to the spatial resolution limit of the instrument. Both monohydrated sulfates (indicated by 2130- and 2400-nm absorptions) and polyhydrated sulfates (indicated by 1450-, 1940-, and 2420-nm absorptions) are evident at all elevations in the ILDs. Polyhydrate signatures occur on intermediate-albedo, relatively intact exposures of stratified material and are rare, but not absent, in nearby erosional debris. Typically the polyhydrate outcrops are low-sloped and form erosion-resistant cap rocks. The monohydrated sulfate also occurs in intermediate- to high-albedo outcrops, but is more commonly distributed as dark, erosional debris on ledges and in depressions that has been modified by wind to form dunes. Only in rare cases can the dark debris be associated with a discrete, dark source layer. The erosional debris exhibits enhancements in sulfate absorptions as well as in 530-, 660-, and 860- to 900-nm absorptions due to ferric iron minerals; different debris

  8. The boron isotope geochemistry of the Kirka borate deposit, western Turkey

    NASA Astrophysics Data System (ADS)

    Palmer, M. R.; Helvaci, C.

    1995-09-01

    We have measured the boron isotope composition of seventeen samples of borate minerals (colemanite, ulexite, and borax) and the 87Sr/ 86Sr ratio in thirteen borate samples from the Kirka borate deposit in western Anatolia, Turkey. These Neogene deposits were formed by evaporation of playa lakes fed by geothermal springs. The δ 11B values range from -14.9% o in colemanite to -1.6% o in borax. To a first approximation the relative differences in the δ 11B values of the borate minerals are consistent with their basic boron atomic configuration, but the magnitude of the boron isotope fractionation between the three minerals precludes their simultaneous precipitation from a brine with the same boron isotope composition and pH. Rather the data are consistent with precipitation of colemanite from a brine with lower pH than that required for ulexite precipitation, which in turn requires a lower pH than is needed for borax precipitation. The boron isotope data also suggest that the borate minerals did not maintain boron isotopic equilibrium with the brine after they precipitated. Rayleigh fractionation models indicate that during borax precipitation the δ 11B value of the brine was slightly heavier than during precipitation of ulexite and colemanite.

  9. Mineralogical characteristics of the superlarge Quaternary bauxite deposits in Jingxi and Debao counties, western Guangxi, China

    NASA Astrophysics Data System (ADS)

    Liu, Xuefei; Wang, Qingfei; Zhang, Qizuan; Feng, Yuewen; Cai, Shuhui

    2012-06-01

    In recent decades, more than 0.5 billion tons of ores scattered in the Quaternary laterite in western Guangxi, China have been explored. The ores were derived from a bauxite horizon in Permian via physical break-up and re-sediment process. Utilizing various test methods, i.e., XRD, DTA, TG/DTG, SEM/EDS and EPMA, the mineralogical characteristics of the Quaternary bauxite ores in Jingxi and Debao counties were investigated. XRD was used together with TG/DTG to obtain relatively accurate ore mineral abundance. Diaspore is the major phase, whereas hematite, kaolinite, anatase, chamosite, gibbsite, goethite, illite and rutile are minor. Diaspore is characterized by a small particle size, low degrees of crystallinity and complex chemical composition. Both gibbsite and goethite have a varied particle size, and goethite crystals contain high Al substitution and Si. It is clarified that diaspore, chamosite and anatase were formed in a mildly reduced and alkaline depositional environment in Permian, while gibbsite, hematite, goethite and part kaolinite were precipitated from Al3+-, Si4+- and Fe3+-enriched solutions within an Quaternary oxidized environment. The ions Al3+, Si4+ and Fe3+ are mostly released from chamosite in its dissolution process. The different physicochemical conditions between the Permian depositional and the Quaternary weathering periods resulted in a complex mineral assemblage in the Quaternary bauxite.

  10. Linked sequence stratigraphy and tectonics in the Sichuan continental foreland basin, Upper Triassic Xujiahe Formation, southwest China

    NASA Astrophysics Data System (ADS)

    Li, Yingjiao; Shao, Longyi; Eriksson, Kenneth A.; Tong, Xin; Gao, Caixia; Chen, Zhongshu

    2014-07-01

    Intracontinental subduction of the South China Block below the North China Block in the Late Triassic resulted in formation of the transpressional Sichuan foreland basin on the South China Block. The Upper Triassic Xujiahe Formation was deposited in this basin and consists of an eastward-tapering wedge of predominantly continental siliciclastic sedimentary rocks that are up to 3.5 km thick in the western foredeep depocenter and thin onto the forebulge and into backbulge depocenters. Five facies associations (A-E) make up the Xujiahe Formation and these are interpreted, respectively, as alluvial fan, transverse and longitudinal braided river, meandering river, overbank or shallow lacustrine, and deltaic deposits. This study establishes a sequence stratigraphic framework for the Xujiahe Formation which is subdivided into four sequences (SQ1, 2, 3 and 4). Sequence boundaries are recognized on the basis of facies-tract dislocations and associated fluvial rejuvenation and incision, and systems tracts are identified based on their constituent facies associations and changes in architectural style and sediment body geometries. Typical sequences consist of early to late transgressive systems tract deposits related to a progressive increase in accommodation and represented by Facies Associations A, B and C that grade upwards into Facies Association D. Regionally extensive and vertically stacked coal seams define maximum accommodation and are overlain by early highstand systems tract deposits represented by Facies Associations D, E and C. Late highstand systems tract deposits are rare because of erosion below sequence boundaries. Sequence development in the Xujiahe Formation is attributed to active and quiescent phases of thrust-loading events and is closely related to the tectonic evolution of the basin. The Sichuan Basin experienced three periods of thrust loading and lithospheric flexure (SQ1, lower SQ2 and SQ3), two periods of stress relaxation and basin widening (upper

  11. Shallow-water marl-limestone alternations in the Late Jurassic of western France: Cycles, storm event deposits or both?

    NASA Astrophysics Data System (ADS)

    Colombié, Claude; Schnyder, Johann; Carcel, Damien

    2012-10-01

    The contribution of event deposits to various basin fills can be very significant, higher than 90% in some cases. Events may lead to the formation of marl-limestone alternations, which can also result from cyclic changes in sea level or climate, for example. The marl-limestone alternations of the Late Jurassic of western France contain abundant coarse-grained accumulations that resemble storm deposits described in other western European successions. The detailed analysis of facies evolution and hierarchical, high-frequency stacking pattern of depositional sequences of the Phare de Chassiron section (Ile d'Oléron, western France) allows the controls on marl-limestone formation to be defined. This section contains nearshore and shallow-marine mud deposits that were exposed to high-energy events. Elementary, small-, and medium-scale depositional sequences are defined. The stacking-pattern and the duration of these sequences suggest an orbital control on sedimentation. Precession (20 ka) cycles notably controlled the formation of elementary sequences that correspond to marl-limestone alternations. The deposition of marly or carbonate mud occurred in this storm-dominated system because of muddy sea beds, the gentle slope of the shelf, and the great amount of particles in suspension, which reduced water energy resulting from storms. Sediment supply was also sufficient to limit bioturbation and favour the preservation of numerous storm deposits. The production of carbonate mud was localised on positive structures and partly controlled by Milankovitch-scale sea-level cycles. Transport by storms of carbonate mud to the adjacent marly depressions during high carbonate production periods led to the formation of calcareous beds. Marl-limestone alternations in the Late Jurassic of western France therefore result from the combined effects of cyclic changes in carbonate production and high-energy, episodic events.

  12. Geology and geochemistry of telluride-bearing Au deposits in the Pingyi area, Western Shandong, China

    NASA Astrophysics Data System (ADS)

    Hu, H.-B.; Mao, J.-W.; Niu, S.-Y.; Li, Y.-F.; Li, M.-W.

    2006-07-01

    Telluride-bearing gold deposits of the Pingyi area, western Shandong, China, are located on the southeastern margin of the North China Craton. There are two main types of deposits: (i) mineralized cryptoexplosive breccia, e.g., Guilaizhuang; and (ii) stratified, finely-disseminated mineralization hosted in carbonate rocks, e.g., Lifanggou and Mofanggou deposits. In Guilaizhuang, the cryptoexplosive breccia is formed within rocks of the Tongshi complex and Ordovician dolomite. The mineralization is controlled by an E-W-trending listric fault. Stratified orebodies of the Lifanggou and Mofanggou deposits are placed along a NE-trending, secondary detachment zone. They are hosted within dolomitic limestone, micrite and dolomite of the Early-Middle Cambrian Changqing Group. The mineralization in the ore districts is considered to be related to the Early Jurassic Tongshi magmatic complex that formed in a continental arc setting on the margin of the North China Craton. The host rocks are porphyritic and consist predominantly of medium- to fine-grained diorite and pyroxene (hornblende)-bearing monzonite. SHRIMP U-Pb zircon dating of diorites give a 206Pb/238U weighted mean age of 175.7 ± 3.8 Ma. This is interpreted as representing the crystallization age of the Tongshi magmatic complex. Considering the contact relationships between the magmatic and host sedimentary rocks, as well as the genetic link with the deposits, we conclude that this age is relevant also for the formation of mineralization in the Pingyi area. We hence consider that the deposits formed in the Jurassic. The principal gold minerals are native gold, electrum and calaverite. Wall-rock alteration comprises pyritization, fluoritization, silicification, carbonatization and chloritization. Fluid inclusion studies indicate that all the analyzed inclusions are of two-phase vapor-liquid NaCl-H2O type. Homogenization temperatures of the fluid inclusions vary from 103 °C to 250 °C, and the ice melting

  13. Rhinocerotidae from the Upper Miocene deposits of the Western Pannonian Basin (Hungary): implications for migration routes and biogeography

    NASA Astrophysics Data System (ADS)

    Pandolfi, Luca; Gasparik, Mihály; Magyar, Imre

    2016-02-01

    Although the rhinoceros remains have high biochronological significance, they are poorly known or scarcely documented in the uppermost Miocene deposits of Europe. Several specimens collected from the Upper Miocene (around 7.0 Ma, Turolian) deposits of Kávás (Pannonian Basin, Western Hungary), previously determined as Rhinoceros sp., are revised and described in this paper. The postcranial remains of these specimens belong to "Dihoplus" megarhinus (de Christol) on the basis of the morphological and morphometric characters of humerus, radii, metacarpal and metatarsal elements. An overview of rhinoceros remains from several uppermost Miocene localities and the revision of the rhinoceros material from the Pannonian Basin suggest that "D." megarhinus spread during the latest Miocene from the Pannonian Basin towards Italy. The occurrences of this species in Western Hungary and Italy during the latest Miocene further imply that Rhinocerotini species were biogeographically segregated between Western, Southern and Central Europe.

  14. Late Quaternary Depositional History and Anthropogenic Impacts of Western Long Island Sound, New York

    NASA Astrophysics Data System (ADS)

    McHugh, C. M.; Cormier, M.; Marchese, P.; Zheng, Y.; Stewart, G.; Acosta, V.; Bowman, A.; Cortes, A.; Leon, L.; Rosa, M.; Semple, D.; Thaker, N.; Vargas, W.; Williams, L.

    2006-12-01

    In June 2006, we surveyed the seafloor of western Long Island Sound with the R/V HUGH SHARP and collected multibeam bathymetry, chirp subbottom profiling, side-scan sonar imagery, and sediment samples (25 gravity cores, 11 multicores, and 10 grabs). In addition, 36 CTD hydrocast stations measured O, pH, alkalinity, trace metals, nutrients, Polonium-210, Lead-210, Thorium-234, organic carbon, and pigments. Continuous weather measurements, and water column properties using both CTD casts and a towed Scanfish were also carried out. Biological sampling included benthic grabs and plankton nets. The National Science Foundation under the "Opportunities to Enhance Diversity in the Geosciences" Program funded this one-week survey. Nine students from underrepresented groups in the geosciences and five P.I.'s participated in the field program. The major scientific objectives were to study the deglaciation of the Laurentide Ice Sheet and Holocene transgression of sea level to document age, sedimentation processes, and climate, and the impact of anthropogenic activities in the sediments, biota, and waters of the estuary. A deep (35 m) and narrow (< 1km) channel incised into bedrock characterizes the East River section of western Long Island Sound. In contrast, thick sedimentary deposits characterize the eastern part of the study area, 20 to 45 km east of New York City. Subbottom penetration reached in some instances 40 m, but is limited to less than 5 m where sediments are gas-charged. Four seismic sequences are imaged in the chirp records that we interpret to span the Last Glacial Maximum to Present: strong irregular erosional surfaces beneath parallel seismic reflectors are interpreted as glacial erosional surface and/or moraines, and as Glacial lake Connecticut sediments ~25 m thick, respectively. A thin veneer (<1 m) of acoustically transparent sediment is interpreted as recent deposits. It overlays a roughly 15 m thick unit interpreted as Holocene transgressive marine

  15. A few Issues about Wenchuan earthquake of 2008, Sichuan, China

    NASA Astrophysics Data System (ADS)

    Cao, J.; Liu, S.; Lu, Z.; Fu, Y.

    2008-12-01

    A devastating earthquake of magnitude 8.0, named Wenchuan earthquake, struck China's Sichuan province on May 12, 2008. The rupture occurred over a length of about 300 km along the northeast-striking Longmen Shan thrust belt. The earthquake resulted in huge casualties and property losses at Longmen Shan region of Sichuan Province, the Southern Shaanxi and Southern Gansu, more than 80,000 people were killed. Longmen Shan is the convergent margin of the eastern Tibetan plateau and Yangtze block. However the area has numerous geological features not typical of active convergent mountain belts. After the earthquake, lots of opinions have been expressed. Basing on field investigation and analysis, we put forward the following opinions: (1) the causative structure of the earthquake may be Pengguan fault, not the Beichuan-Yingxiu fault (central fault)£»(2) the uplift of the Longmen Shan and the earthquakes in Longmen Shan may be controlled by the bilateral stresses from the Songpan -Ganzi block on the west side and Sichuan basin on the east side; (3) by calculating the balance between the accumulation and dissipation of the compressed strain energy, we may make out an estimation of the rhythm of strong Earthquake in Longmen Shan; (4) By analyzing the pressure data measured at oil or gas producing wells, we may monitor the changes of the earth stress in deep; (5) Earthquakes in Longmen Shan may be favorable to the forming of the fractured reservoir and hydrocarbon accumulation in Western Sichuan depression. The work was supported by NSFC under grant No.40739907

  16. Nitrogen deposition to lakes in national parks of the western Great Lakes region: Isotopic signatures, watershed retention, and algal shifts

    NASA Astrophysics Data System (ADS)

    Hobbs, William O.; Lafrancois, Brenda Moraska; Stottlemyer, Robert; Toczydlowski, David; Engstrom, Daniel R.; Edlund, Mark B.; Almendinger, James E.; Strock, Kristin E.; VanderMeulen, David; Elias, Joan E.; Saros, Jasmine E.

    2016-03-01

    Atmospheric deposition is a primary source of reactive nitrogen (Nr) to undisturbed watersheds of the Great Lakes region of the U.S., raising concerns over whether enhanced delivery over recent decades has affected lake ecosystems. The National Atmospheric Deposition Program (NADP) has been measuring Nr deposition in this region for over 35 years. Here we explore the relationships among NADP-measured Nr deposition, nitrogen stable isotopes (δ15N) in lake sediments, and the response of algal communities in 28 lakes situated in national parks of the western Great Lakes region of the U.S. We find that 36% of the lakes preserve a sediment δ15N record that is statistically correlated with some form of Nr deposition (total dissolved inorganic N, nitrate, or ammonium). Furthermore, measured long-term (since 1982) nitrogen biogeochemistry and inferred critical nitrogen loads suggest that watershed nitrogen retention and climate strongly affect whether sediment δ15N is related to Nr deposition in lake sediment records. Measurements of algal change over the last ~ 150 years suggest that Nr deposition, in-lake nutrient cycling, and watershed inputs are important factors affecting diatom community composition, in addition to direct climatic effects on lake physical limnology. The findings suggest that bulk sediment δ15N does reflect Nr deposition in some instances. In addition, this study highlights the interactive effects of Nr deposition and climate variability.

  17. Radiostratigraphic study of the deposits of the Maikop Group, Western Azerbaijan

    NASA Astrophysics Data System (ADS)

    Efendieva, M.; Babaev, R.; Johnson, C.; Feyzullayev, A.; Aliev, Ch.

    2012-11-01

    This work presents the results of biostratigraphic study of natural outcrops of the Maikop Group, which were first carried together with detailed radiometric studies in the Ganja oil and gas-bearing region, Western Azerbaijan. The paleontological research method included determination of the genus or species (depending on the preservation) of microfaunistic remains (foraminifera, ostracods, fish remains). The radiometric research method included measurements of the integral radioactivity in the field, the sampling, as well as laboratory radionuclide (spectral) analysis. As a result of our research, the stratigraphic control of variation in the radioactivity of rocks of the Maikop Group of the Ganja oil and gas-bearing region has been established. The radioactivity of Oligocene rocks is predominantly determined by potassium content. The radioactivity of the Miocene part of the section of the Maikop Group is determined by uranium-potassium contents. Within the Ganja oil and gas-bearing region, deposits of the Kotsakhurian regional stage, which are usually referred to "barren" formations or anoxic "fish facies", contain a significant number of species of benthic foraminiferal fauna.

  18. Pliocene-Pleistocene continental deposits in western Kentucky: A new look at regional stratigraphy and depositional history

    SciTech Connect

    Phillips, B.E. )

    1992-01-01

    Pliocene and Pleistocene age sediments of the northernmost Mississippi Embayment consist of a thick sequence of continental deposits which rest unconformably on Cretaceous through Eocene strata. The continental deposits have been tentatively correlated to the Pliocene Mounds Gravel and Pleistocene Henry and Equality Formations of southern Illinois. These sediments have previously been interpreted as representing alluvial fan and fluvial deposits. The continental deposits are generally divided into three lithofacies: (1) silt/clay dominated; (2) sand dominated, and (3) gravel dominated. A subsurface study utilizing approximately 300 soil borings has shown that (1) the continental deposits, particularly the gravel facies, exhibit significant local changes in thickness, (2) the upper portion of the sequence consists predominantly of finer-grained silt/clay lithofacies, and (3) sand and gravel lithofacies within the upper sequence often occur at predictable horizons. These observations indicate a paleovalley fill with distinct depositional episodes. As a result of Pleistocene base level fluctuations, stream systems became deeply entrenched in the Pliocene alluvial fan and older sediments. Fan deposits were initially transported and redeposited in a braided fluvial system. As valley alluviation continued and gradients decreased, the braided fluvial system evolved into a meandering system. During Woodfordian time, slackwater lakes created by glacial outwash dams produced extensive lacustrine deposits. At least two major episodes of lacustrine sedimentation are apparent. Significant fluctuations of lake level are recognized in the subsurface by local erosional surfaces overlain by coarser-grained sediments deposited in basinward-migrating channel and shoreline facies.

  19. Inorganic nitrogenous air pollutants, atmospheric nitrogen deposition and their potential ecological impacts in remote areas of western North America (Invited)

    NASA Astrophysics Data System (ADS)

    Bytnerowicz, A.; Fenn, M. E.; Fraczek, W.; Johnson, R.; Allen, E. B.

    2013-12-01

    Dry deposition of gaseous inorganic nitrogenous (N) air pollutants plays an important role in total atmospheric N deposition and its ecological effects in the arid and semi-arid ecosystems. Passive samplers and denuder/ filter pack systems have been used for determining ambient concentrations of ammonia (NH3), nitric oxide (NO), nitrogen dioxide (NO2), and nitric acid vapor (HNO3) in the topographically complex remote areas of the western United States and Canada. Concentrations of the measured pollutants varied significantly between the monitoring areas. Highest NH3, NO2 and HNO3 levels occurred in southern California areas downwind of the Los Angeles Basin and in the western Sierra Nevada impacted by emissions from the California Central Valley and the San Francisco Bay area. Strong spatial gradients of N pollutants were also present in southeastern Alaska due to cruise ship emissions and in the Athabasca Oil Sands Region in Canada affected by oil exploitation. Distribution of these pollutants has been depicted by maps generated by several geostatistical methodologies within the ArcGIS Geostatistical Analyst (ESRI, USA). Such maps help to understand spatial and temporal changes of air pollutants caused by various anthropogenic activities and locally-generated vs. long range-transported air pollutants. Pollution distribution maps for individual N species and gaseous inorganic reactive nitrogen (Nr) have been developed for the southern portion of the Sierra Nevada, Lake Tahoe Basin, San Bernardino Mountains, Joshua Tree National Park and the Athabasca Oil Sands Region. The N air pollution data have been utilized for estimates of dry and total N deposition by a GIS-based inferential method specifically developed for understanding potential ecological impacts in arid and semi-arid areas. The method is based on spatial and temporal distribution of concentrations of major drivers of N dry deposition, their surface deposition velocities and stomatal conductance values

  20. Depositional settings, correlation, and age carboniferous rocks in the western Brooks Range, Alaska

    USGS Publications Warehouse

    Dumoulin, J.A.; Harris, A.G.; Blome, C.D.; Young, L.E.

    2004-01-01

    The Kuna Formation (Lisburne Group) in northwest Alaska hosts the Red Dog and other Zn-Pb-Ag massive sulfide deposits in the Red Dog district. New studies of the sedimentology and paleontology of the Lisburne Group constrain the setting, age, and thermal history of these deposits. In the western and west-central Brooks Range, the Lisburne Group includes both deep- and shallow-water sedimentary facies and local volcanic rocks that are exposed in a series of thrust sheets or allochthons. Deep-water facies in the Red Dog area (i.e., the Kuna Formation and related rocks) are found chiefly in the Endicott Mountains and structurally higher Picnic Creek allochthons. In the Red Dog plate of the Endicott Mountains allochthon, the Kuna consists of at least 122 m of thinly interbedded calcareous shale, calcareous spiculite, and bioclastic supportstone (Kivalina unit) overlain by 30 to 240 m of siliceous shale, mudstone, calcareous radiolarite, and calcareous lithic turbidite (Ikalukrok unit). The Ikalukrok unit in the Red Dog plate hosts all massive sulfide deposits in the area. It is notably carbonaceous, is generally finely laminated, and contains siliceous sponge spicules and radiolarians. The Kuna Formation in the Key Creek plate of the Endicott Mountains allochthon (60-110 m) resembles the Ikalukrok unit but is unmineralized and has thinner carbonate layers that are mainly organic-rich dolostone. Correlative strata in the Picnic Creek allochthon include less shale and mudstone and more carbonate (mostly calcareous spiculite). Conodonts and radiolarians indicate an age range of Osagean to early Chesterian (late Early to Late Mississippian) for the Kuna in the Red Dog area. Sedimentologic, faunal, and geochemical data imply that most of the Kuna formed in slope and basin settings characterized by anoxic or dysoxic bottom water and by local high productivity. Shallow-water facies of th e Lisburne Group in the Red Dog area are present locally in the Endicott Mountains

  1. Critical nitrogen deposition loads in high-elevation lakes of the western US inferred from paleolimnological records

    USGS Publications Warehouse

    Saros, J.E.; Clow, D.W.; Blett, T.; Wolfe, A.P.

    2011-01-01

    Critical loads of nitrogen (N) from atmospheric deposition were determined for alpine lake ecosystems in the western US using fossil diatom assemblages in lake sediment cores. Changes in diatom species over the last century were indicative of N enrichment in two areas, the eastern Sierra Nevada, starting between 1960 and 1965, and the Greater Yellowstone Ecosystem, starting in 1980. In contrast, no changes in diatom community structure were apparent in lakes of Glacier National Park. To determine critical N loads that elicited these community changes, we modeled wet nitrogen deposition rates for the period in which diatom shifts first occurred in each area using deposition data spanning from 1980 to 2007. We determined a critical load of 1.4 kg N ha-1 year-1 wet N deposition to elicit key nutrient enrichment effects on diatom communities in both the eastern Sierra Nevada and the Greater Yellowstone Ecosystem. ?? 2010 Springer Science+Business Media B.V.

  2. Volatile element isotopes of submarine hydrothermal mineral deposits in the Western Pacific

    NASA Astrophysics Data System (ADS)

    Ooki, Mitsuhiro; Kagoshima, Takanori; Takahata, Naoto; Ishibashi, Jun-ichiro; Lan, Tefang; Guo, Zhengfu; Sano, Yuji

    2016-06-01

    The abundance and isotopic compositions of volatile elements trapped in fluid inclusions of submarine hydrothermal mineral deposits in Western Pacific subduction zones (Okinawa Trough, Izu-Bonin arc, Mariana Trough, and Lau Basin) and in Kuroko ores in northeastern Japan are presented. The helium isotopic compositions corrected for air contribution of the Okinawa and Mariana troughs, ranging 4.49-7.68 Ra are lower than those of the Izu-Bonin and Lau Basin, 7.62-8.91 Ra. This characteristic might reflect the differences in regional tectonic setting. The Okinawa and Mariana troughs are related to back-arc spreading with strong graben sedimentary signature, whereas the Izu-Bonin arc is associated with island arc magmatism. The arc contribution to the Lau Basin volcanism is significantly strong, even though it is assigned to back-arc spreading. Nitrogen isotopes can also be explained by a similar hypothesis, whereas argon and carbon isotopes cannot be used to discriminate tectonic setting. δ13C-CO2/3He and δ15N-N2/36Ar diagrams elucidate the source of carbon and nitrogen. The MOR-type mantle contributions to carbon are mostly smaller in the Okinawa and Mariana troughs (ranging 0.06-8.9% with the average of 2.4%) than in the Izu-Bonin and Lau Basin (2.1-25% with the average of 7.7%). The sedimentary contributions to nitrogen are larger in the Okinawa and Mariana troughs (11-65% with the average of 35%) than in the Izu-Bonin and Lau Basin (4-24% with the average of 15%), and the Kuroko samples agree well with the latter. Carbon and nitrogen fluxes are again higher in Okinawa trough than in Izu-Bonin arc.

  3. Hydrothermal fluids circulation and travertine deposition in an active tectonic setting: Insights from the Kamara geothermal area (western Anatolia, Turkey)

    NASA Astrophysics Data System (ADS)

    Brogi, Andrea; Alçiçek, M. Cihat; Yalçıner, Cahit Çağlar; Capezzuoli, Enrico; Liotta, Domenico; Meccheri, Marco; Rimondi, Valentina; Ruggieri, Giovanni; Gandin, Anna; Boschi, Chiara; Büyüksaraç, Aydin; Alçiçek, Hülya; Bülbül, Ali; Baykara, Mehmet Oruç; Shen, Chuan-Chou

    2016-06-01

    Coexistence of thermal springs, travertine deposits and tectonic activity is a recurring feature for most geothermal areas. Although such a certainty, their relationships are debated mainly addressing on the role of the tectonic activity in triggering and controlling fluids flow and travertine deposition. In this paper, we present the results of an integrated study carried out in a geothermal area located in western Anatolia (Turkey), nearby the well-known Pamukkale area (Denizli Basin). Our study focused on the relationships among hydrothermal fluids circulation, travertine deposition and tectonic activity, with particular emphasis on the role of faults in controlling fluids upwelling, thermal springs location and deposition of travertine masses. New field mapping and structural/kinematics analyses allowed us to recognize two main faults systems (NW- and NE-trending), framed in the Neogene-Quaternary extensional tectonic evolution of western Anatolia. A geo-radar (GPR) prospection was also provided in a key-area, permitting us to reconstruct a buried fault zone and its relationships with the development of a fissure-ridge travertine deposit (Kamara fissure-ridge). The integration among structural and geophysical studies, fluids inclusion, geochemical, isotopic data and 230 Th/238 U radiometric age determination on travertine deposits, depict the characteristics of the geothermal fluids and their pathway, up to the surface. Hydrological and seismological data have been also taken in account to investigate the relation between local seismicity and fluid upwelling. As a main conclusion we found strict relationships among tectonic activity, earthquakes occurrence, and variation of the physical/chemical features of the hydrothermal fluids, presently exploited at depth, or flowing out in thermal springs. In the same way, we underline the tectonic role in controlling the travertine deposition, making travertine (mainly banded travertine) a useful proxy to reconstruct the

  4. Geomorphology and regional stratigraphic model of Cenozoic deposits from "Continental to Marine" of Western Peninsular Malaysia and Strait of Malacca.

    NASA Astrophysics Data System (ADS)

    Menier, David; Mansor, Yazid; Sautter, Benjamin; Pubellier, Manuel; Estournes, Guilhem; Meng Choong, Chee; Ghosh Deva, Prasad; Proust, Jean-Noel; Goubert, Evelyne

    2014-05-01

    Coastal basins have been greatly influenced worldwide by their geological heritage (lithology, structural control) and eustatic sea-level fluctuations. Along the western side of Peninsular Malaysia, both the structures of the tertiary-quaternary basement and the geomorphology are poorly known. The coast is characterized landward by an absence of tertiary deposits on the alluvial and coastal plains and seaward by numerous deeply incised valleys although the incision potential is low. Offshore, in the Strait of Malacca, the thickness of sediments increases drastically, particularly at the apex of some N-S elongated basins (> 2 Km), and in the central part of the Strait of Malacca. Onshore, the geomorphology of the Western Peninsular Malaysia is controlled mostly by climatic effects on an old (Indosinian) orogen affected by transtensional brittle tectonics during the Tertiary. We investigate the effects of Tertiary extension and associated vertical motions on the Cenozoic geomorphology and stratigraphy. The study is based on a combined morphobathymetric approach of based on GEBCO data, supported by low and recent high resolution offshore seismic data, and DTM data from ASTER and SRTM. The main results are the followings: (1) the structural control appears to be responsible of the positioning and preservation of the Tertiary deposits; while the Quaternary (marine) deposits thinner, drowned the western Malaysia Peninsular coast, independently of the geomorphological and structural context; (2) The offshore Tertiary deposits seem disconnected from the modern drainage network, suggesting probable uplift during the late Tertiary period, which reactivated NW-SE trending faults and fractures; (3) The orientation, the shape and the depth of the ancient and modern incised valleys (Perak, Kerian , Kinta rivers) are controlled by the structural context and lithological contrast; (4) Finally, from a landward to a seaward directions, the Cenozoic deposits seems to have transited

  5. Geologic Setting of the May 12, 2008, Sichuan Earhquake

    NASA Astrophysics Data System (ADS)

    Burchfiel, B. C.; Royden, L. H.

    2008-12-01

    The May 12, 2008, Sichuan earthquake was located in the Longmen Shan, mountains that form the eastern margin of the Tibetan plateau and border the western side of the Sichuan basin. The region of the Longmen Shan consists of very complex structures that vary greatly along strike. Geologically, the Longmen Shan lie along the western margin of the Yangtze craton and was first deformed in late Triassic-early Jurassic (Indosinian) time when the margin was telescoped by large scale eastward thrusting and development of an adjacent Mesozoic foredeep. These units can be followed from their join with the Qinling Mountains in the north, south into central Yunnan. Although there are suggestions of younger Mesozoic deformation, the next major deformation that can be documented is late Cenozoic (beginning ~12 Ma) with the formation of diverse structures. South of the Sichuan basin folds and thrust faults form a multiply deformed area that involves Precambrian basement rocks and Phanerozoic sedimentary rocks with a modified dome and basin interference pattern. These folds and thrust fault project northward into the southern Sichuan basin where most of them end within the basin, but the Longchuan anticline on the east and several folds on the west continue north; the Longchuan anticline curves west into the middle of the Longmen Shan and the western structures form the eastern margin of the NE-trending Longmen Shan. At this latitude the structures involve only Mesozoic rocks above a decollement that underlies the Chengdu plain, but ramps down to the west beneath Precambrian cored structures that form the core of the Longmen Shan. These basement involved structures have a modified fault propagation fold geometry. Northward, the margin of the Tibetan plateau curves to the west along the N-S trending Min Shan formed by active east-vergent steep thrust faults. These structures may be localized by crustal anisotropy between the Xue Shan plateau and Song Pan Ganze flysch basin. A

  6. Holocene hillslope processes and deposits in two U-shaped mountain valleys in western Norway

    NASA Astrophysics Data System (ADS)

    Laute, K.; Beylich, A. A.

    2012-04-01

    This doctoral research project is integrated in the Norwegian Research Council (NFR) funded SedyMONT-Norway Project within the ESF EUROCORES TOPO-EUROPE SedyMONT (Timescales of sediment dynamics, climate and topographic change in mountain landscapes) Programme. Research is carried out within two steep, U-shaped and glacier-connected tributary valleys (Erdalen and Bødalen) on the western side of the Jostedalsbreen ice cap in western Norway. Contemporary denudative processes in both valley systems include rock and boulder falls, avalanches, slush flows, debris flows, creep processes, wash- and chemical denudation and fluvial transport of solutes, suspended sediments and bedload. The main aims of this research project which are approached within a Holocene to contemporary timescale are: (i) to investigate the spatio-temporal variability of Holocene hillslope development, (ii) to analyse more specificly the morphometric influences and geomorphic consequences of the Little Ice Age (LIA) glacier advance on selected hillslope systems within defined headwater areas in both valleys, (iii) to study morphometric and meteorological controls of contemporary denudative slope processes as well as (iv) to quantify the rates of sediment delivery from headwater areas and its changes over time. A process-based approach is applied using a variety of different methods and techniques. Focus is on different temporal (Holocene to contemporary) and spatial (selected hillslope systems, headwater areas and entire valley system) scales. The applied methods include orthophoto- and topographical map interpretation, GIS and DEM computing, geomorphological fieldmapping and hillslope profile surveying complemented by relative dating techniques (lichenometry and dendrochronology), geophysical investigations and terrestrial laser scanning (LIDAR). For monitoring contemporary rates of slope processes a designed monitoring programme (running since 2009) with a wide spectrum of instrumentation; e

  7. Electrical and geochemical properties of tufa deposits as related to mineral composition in the South Western Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Gomaa, Mohamed M.; Abou El-Anwar, Esmat A.

    2015-06-01

    The geochemical, petrographical, and electrical properties of rocks are essential to the investigation of the properties of minerals. In this paper we will try to present a study of the A. C. electrical properties of carbonate rock samples and their relation to petrographical and geochemical properties. Samples were collected from four formations from the Bir Dungul area, in the South Western Desert, Egypt. The electrical properties of the samples were measured using a non-polarizing electrode, at room temperature (~28 °C), and at a relative atmospheric humidity of (~45%), in the frequency range from 42 Hz to 5 MHz. The changes in the electrical properties were argued to the change in mineral composition. Generally, the electrical properties of rocks are changed due to many factors e.g., grain size, mineral composition, grain shape and inter-granular relations between grains. The dielectric constant of samples decreases with frequency, and increases with conductor concentration. Also, the conductivity increases with an increase of continuous conductor paths between electrodes. The petrographical and geochemical studies reveal that the deposition of the tufa deposits occurred in shallow lakes accompanied by a high water table, an alkaline spring recharge and significant vegetation cover. Diagenetically, tufa deposits were subjected to early and late diagenesis. Petrography and geochemistry studies indicated that the area of tufa deposits was deposited under the control of bacterial activity. Geochemically, the Sr content indicates that the tufa deposits formed from dissolved bicarbonate under the control of microbes and bacterial activity.

  8. Paleotopographic control of landslides in lacustrine deposits (Trièves plateau, French western Alps)

    NASA Astrophysics Data System (ADS)

    Bièvre, Grégory; Kniess, Ulrich; Jongmans, Denis; Pathier, Erwan; Schwartz, Stéphane; van Westen, Cees J.; Villemin, Thierry; Zumbo, Vilma

    2011-01-01

    Paleotopography in Quaternary sedimentary environments can be an important factor that controls landslide movement. This study investigates the relation between paleotopography and landslide activity in two adjacent landslides in glaciolacustrine sediments located in the Trièves area (French western Alps). Although both are in slopes underlain by the same lacustrine deposits, the Avignonet and Harmalière landslides exhibit major differences in morphology and displacement rates. Through a combination of geological mapping, airborne light detection and ranging (LiDAR) data, aerial photographs, global positioning system (GPS), and seismic noise measurements, a three-dimensional impression was made of both landslides. The analysis reveals that the difference in kinematics between the two mass movements can be traced back to at least 50 years ago. The results show that the Harmalière slide, which failed catastrophically in 1981, is still much more active than the Avignonet landslide. The fear was that the Avignonet landslide might develop in a similar catastrophic manner, threatening a number of houses constructed on the landslide. A geophysical survey based on ambient noise measurements allowed us to map the base of the lacustrine clays, and the results indicate the presence of a N-S ridge of hard sediments (Jurassic bedrock and/or compact alluvial layers) on the eastern side of the Avignonet landslide. This ridge disappears when approaching the Harmalière landslide and makes a place to what can be interpreted as a NW-SE oriented paleovalley of the river Drac. We proposed that the ridge acts as a buttress that could mechanically prevent the Avignonet landslide from evolving as fast as the Harmalière. Furthermore, the NW-SE paleovalley located under the Harmalière landslide corresponds to the motion direction of the slide. Therefore, the different behaviour of the two landslides is partly controlled by the paleotopographic setting of Lake Trièves during the last

  9. Mineralogical and geochemical characteristics of the Archaean LCT pegmatite deposit Cattlin Creek, Ravensthorpe, Western Australia

    NASA Astrophysics Data System (ADS)

    Bauer, Matthias; Dittrich, Thomas; Seifert, Thomas; Schulz, Bernhard

    2014-05-01

    The LCT (lithium-cesium-tantalum) pegmatite Cattlin Creek is located about 550 km ESE of Perth, Western Australia. The complex-type, rare-element pegmatite is hosted in metamorphic rocks of the Archaean Ravensthorpe greenstone belt, which constitutes of the southern edge of the Southern Cross Terranes of the Yilgarn Craton. The deposit is currently mined for both lithium and tantalum by Galaxy Resources Limited since 2010. The pegmatitic melt intruded in a weak structural zone of crossing thrust faults and formed several pegmatite sills, of which the surface nearest mineralized pegmatite body is up to 21 m thick. The Cattlin Creek pegmatite is characterized by an extreme fractionation that resulted in the enrichment of rare elements like Li, Cs, Rb, Sn and Ta, as well as the formation of a vertical zonation expressed by distinct mineral assemblages. The border zone comprises a fine-grained mineral assemblage consisting of albite, quartz, muscovite that merges into a medium-grained wall zone and pegmatitic-textured intermediate zones. Those zones are manifested by the occurrence of megacrystic spodumene crystals with grain sizes ranging from a couple of centimeters up to several metres. The core zone represents the most fractionated part of the pegmatite and consists of lepidolite, cleavelandite, and quartz. It also exhibits the highest concentrations of Cs (0.5 wt.%), Li (0.4 wt.%), Rb (3 wt.%), Ta (0.3 wt.%) and F (4 wt.%). This zone was probably formed in the very last crystallization stage of the pegmatite and its minerals replaced earlier crystallized mineral assemblages. Moreover, the core zone hosts subordinate extremely Cs-enriched (up to 13 wt.% Cs2O) mineral species of beryl. The chemical composition of this beryl resamples that of the extreme rare beryl-variety pezzotaite. Other observed subordinate, minor and accessory minerals comprise tourmaline, garnet, cassiterite, apatite, (mangano-) columbite, tantalite, microlite (Bi-bearing), gahnite, fluorite

  10. Nahcolite and halite deposition through time during the saline mineral phase of Eocene Lake Uinta, Piceance Basin, western Colorado

    USGS Publications Warehouse

    Johnson, Ronald C.; Brownfield, Michael E.

    2013-01-01

    Halite and the sodium bicarbonate mineral nahcolite were deposited during the saline phase of Eocene Lake Uinta in the Piceance Basin, western Colorado. Variations in the area of saline mineral deposition through time were interpreted from studies of core and outcrop. Saline minerals were extensively leached by groundwater, so the original extent of saline deposition was estimated from the distribution of empty vugs and collapse breccias. Vugs and breccias strongly influence groundwater movement, so determining where leaching has occurred is an important consideration for in-situ oil shale extraction methods currently being developed. Lake Uinta formed when two smaller fresh water lakes, one in the Uinta Basin of eastern Utah and the other in the Piceance Basin of western Colorado, expanded and coalesced across the Douglas Creek arch, an area of comparatively low subsidence rates. Salinity increased shortly after this expansion, but saline mineral deposition did not begin until later, after a period of prolonged infilling created broad lake-margin shelves and a comparatively small deep central lake area. These shelves probably played a critical role in brine evolution. A progression from disseminated nahcolite and nahcolite aggregates to bedded nahcolite and ultimately to bedded nahcolite and halite was deposited in this deep lake area during the early stages of saline deposition along with rich oil shale that commonly shows signs of slumping and lateral transport. The area of saline mineral and rich oil shale deposition subsequently expanded, in part due to infilling of the compact deep area, and in part because of an increase in water flow into Lake Uinta, possibly due to outflow from Lake Gosiute to the north. Finally, as Lake Uinta in the Piceance Basin was progressively filled from north to south by volcano-clastic sediment, the saline depocenter was pushed progressively southward, eventually covering much of the areas that had previously been marginal shelves

  11. Mass-movement deposits in the lacustrine Eocene Green River Formation, Piceance Basin, western Colorado

    USGS Publications Warehouse

    Johnson, Ronald C.; Birdwell, Justin E.; Brownfield, Michael E.; Mercier, Tracey J.

    2015-01-01

    The Eocene Green River Formation was deposited in two large Eocene saline lakes, Lake Uinta in the Uinta and Piceance Basins and Lake Gosiute in the Greater Green River Basin. Here we will discuss mass-movement deposits in just the Piceance Basin part of Lake Uinta.

  12. Magmatism and Epithermal Gold-Silver Deposits of the Southern Ancestral Cascade Arc, Western Nevada and Eastern California

    USGS Publications Warehouse

    John, David A.; du Bray, Edward A.; Henry, Christopher D., (compiler); Vikre, Peter

    2015-01-01

    Many epithermal gold-silver deposits are temporally and spatially associated with late Oligocene to Pliocene magmatism of the southern ancestral Cascade arc in western Nevada and eastern California. These deposits, which include both quartz-adularia (low- and intermediate-sulfidation; Comstock Lode, Tonopah, Bodie) and quartz-alunite (high-sulfidation; Goldfield, Paradise Peak) types, were major producers of gold and silver. Ancestral Cascade arc magmatism preceded that of the modern High Cascades arc and reflects subduction of the Farallon plate beneath North America. Ancestral arc magmatism began about 45 Ma, continued until about 3 Ma, and extended from near the Canada-United States border in Washington southward to about 250 km southeast of Reno, Nevada. The ancestral arc was split into northern and southern segments across an inferred tear in the subducting slab between Mount Shasta and Lassen Peak in northern California. The southern segment extends between 42°N in northern California and 37°N in western Nevada and was active from about 30 to 3 Ma. It is bounded on the east by the northeast edge of the Walker Lane. Ancestral arc volcanism represents an abrupt change in composition and style of magmatism relative to that in central Nevada. Large volume, caldera-forming, silicic ignimbrites associated with the 37 to 19 Ma ignimbrite flareup are dominant in central Nevada, whereas volcanic centers of the ancestral arc in western Nevada consist of andesitic stratovolcanoes and dacitic to rhyolitic lava domes that mostly formed between 25 and 4 Ma. Both ancestral arc and ignimbrite flareup magmatism resulted from rollback of the shallowly dipping slab that began about 45 Ma in northeast Nevada and migrated south-southwest with time. Most southern segment ancestral arc rocks have oxidized, high potassium, calc-alkaline compositions with silica contents ranging continuously from about 55 to 77 wt%. Most lavas are porphyritic and contain coarse plagioclase

  13. Rujevac Sb-Pb-Zn-As polymetallic deposit, Boranja orefield, Western Serbia: native arsenic and arsenic mineralization

    NASA Astrophysics Data System (ADS)

    Radosavljević, Slobodan A.; Stojanović, Jovica N.; Radosavljević-Mihajlović, Ana S.; Vuković, Nikola S.

    2014-02-01

    Rujevac is a low-temperature hydrothermal polymetallic Sb-Pb-Zn-As vein-type ore deposit, hosted within a volcanogenic-sedimentary zone situated in the Rujevac-Crvene Stene-Brezovica Diabase-Chert Formation (DCF) of the Podrinje Metallogenic District (PMD), Serbia. It is located several kilometers SE from the Boranja contact aureole, which is an integral part of the PMD in Western Serbia. Genetically related to the Tertiary granodioritic magma, the mineral assemblages are characterized by specific features. The mineral association of this deposit consists of sulfides, Pb-Sb(As) sulfosalts, native metals, oxides, hydroxides and gangue minerals. Chemical composition of the ore is very complex, where contents of valuable metals range as follows: Sb (0.17-24.31 wt.%), Zn (0.21-6.29 wt.%), Pb (0.15-6.33 wt.%), As (0.06-1.28 wt.%), Cd (25-747 ppm), Ag (7-408 ppm), Hg (13-473 ppm), and Tl (<1-29 ppm). Electron Probe Microanalyses (EPMA) of native arsenic from both the Rujevac and Stragari deposits showed contents of As up to 98.8 and 97.1 wt.%, with impurity contents of Sb up to 1.3 and 6.6 wt.%, and Tl up to 2 and 1.3 wt.%, respectively. Rhombohedral unit-cell parameters for native arsenic from Rujevac and Stragari deposits amount to: a = 3.760(2), c = 10.555(3) Å, V = 129.23(7) Å3 and a = 3.763(1), c = 10.560(5) Å, V = 129.48(8) Å3, respectively. Mineral assemblages, deposition order and genesis of the Rujevac polymetallic deposit were also discussed in detail. Native arsenic mineralization here has been additionally compared with similar well-known global deposits.

  14. Rujevac Sb-Pb-Zn-As polymetallic deposit, Boranja orefield, Western Serbia: native arsenic and arsenic mineralization

    NASA Astrophysics Data System (ADS)

    Radosavljević, Slobodan A.; Stojanović, Jovica N.; Radosavljević-Mihajlović, Ana S.; Vuković, Nikola S.

    2013-05-01

    Rujevac is a low-temperature hydrothermal polymetallic Sb-Pb-Zn-As vein-type ore deposit, hosted within a volcanogenic-sedimentary zone situated in the Rujevac-Crvene Stene-Brezovica Diabase-Chert Formation (DCF) of the Podrinje Metallogenic District (PMD), Serbia. It is located several kilometers SE from the Boranja contact aureole, which is an integral part of the PMD in Western Serbia. Genetically related to the Tertiary granodioritic magma, the mineral assemblages are characterized by specific features. The mineral association of this deposit consists of sulfides, Pb-Sb(As) sulfosalts, native metals, oxides, hydroxides and gangue minerals. Chemical composition of the ore is very complex, where contents of valuable metals range as follows: Sb (0.17-24.31 wt.%), Zn (0.21-6.29 wt.%), Pb (0.15-6.33 wt.%), As (0.06-1.28 wt.%), Cd (25-747 ppm), Ag (7-408 ppm), Hg (13-473 ppm), and Tl (<1-29 ppm). Electron Probe Microanalyses (EPMA) of native arsenic from both the Rujevac and Stragari deposits showed contents of As up to 98.8 and 97.1 wt.%, with impurity contents of Sb up to 1.3 and 6.6 wt.%, and Tl up to 2 and 1.3 wt.%, respectively. Rhombohedral unit-cell parameters for native arsenic from Rujevac and Stragari deposits amount to: a = 3.760(2), c = 10.555(3) Å, V = 129.23(7) Å3 and a = 3.763(1), c = 10.560(5) Å, V = 129.48(8) Å3, respectively. Mineral assemblages, deposition order and genesis of the Rujevac polymetallic deposit were also discussed in detail. Native arsenic mineralization here has been additionally compared with similar well-known global deposits.

  15. High Elevation Lakes of the Western US: Are we Studying Systems Recovering from Excess Atmospheric Deposition of Acids and Nutrients?

    NASA Astrophysics Data System (ADS)

    Sickman, J. O.

    2011-12-01

    Instrumental records and monitoring of high elevation lakes began in most areas of the western US in the early 1980s. Much effort has been devoted to detecting changes in these aquatic ecosystems resulting from increased atmospheric deposition of acids and nutrients. However, there is growing evidence that thresholds for atmospheric pollutants were crossed much earlier in the 20th Century and that some of the subsequent hydrochemical and ecological changes observed in these lakes may be the result of recovery from earlier atmospheric forcing. We examine responses of high elevation lakes to atmospheric deposition on annual to century timescales using data from a 29-year study of Emerald Lake (Sequoia National Park) and paleolimnological analyses of other high elevation lakes incorporating diatom species analyses and geochemical proxies for fossil-fuel burning. At Emerald Lake, we have observed multiple transitions between nitrogen and phosphorus limitation of phytoplankton, the earliest of which occurred in the beginning of the 1980s and may be the result of reduction in N deposition due to the Clean Air Act. Critical loads analyses incorporating diatom species in lake sediments suggest that thresholds for N deposition were crossed in the period of 1950-1980 in the Rocky Mountains and likely much earlier, 1900-1920, in the Sierra Nevada. Diatom species composition is strongly controlled by acid neutralizing capacity (ANC) in the Sierra Nevada and we have observed a pronounced decline and recovery of ANC over the period of 1920-1980 in some Sierra Nevada lakes that coincides with the abundance of spheroidal carbonaceous particles (i.e., a diagnostic tracer of fossil fuel combustion) preserved in lake sediments; these patterns appear to be driven by increased emissions of oxidized N and S in the mid-20th Century and reductions in acid precursor levels caused by the Clean Air Act in the 1970s. Thus, when interpreting observational records from western high elevation

  16. A late quaternary record of eolian silt deposition in a maar lake, St. Michael Island, western Alaska

    USGS Publications Warehouse

    Muhs, D.R.; Ager, T.A.; Been, J.; Bradbury, J.P.; Dean, W.E.

    2003-01-01

    Recent stratigraphic studies in central Alaska have yielded the unexpected finding that there is little evidence for full-glacial (late Wisconsin) loess deposition. Because the loess record of western Alaska is poorly exposed and not well known, we analyzed a core from Zagoskin Lake, a maar lake on St. Michael Island, to determine if a full-glacial eolian record could be found in that region. Particle size and geochemical data indicate that the mineral fraction of the lake sediments is not derived from the local basalt and is probably eolian. Silt deposition took place from at least the latter part of the mid-Wisconsin interstadial period through the Holocene, based on radiocarbon dating. Based on the locations of likely loess sources, eolian silt in western Alaska was probably deflated by northeasterly winds from glaciofluvial sediments. If last-glacial winds that deposited loess were indeed from the northeast, this reconstruction is in conflict with a model-derived reconstruction of paleowinds in Alaska. Mass accumulation rates in Zagoskin Lake were higher during the Pleistocene than during the Holocene. In addition, more eolian sediment is recorded in the lake sediments than as loess on the adjacent landscape. The thinner loess record on land may be due to the sparse, herb tundra vegetation that dominated the landscape in full-glacial time. Herb tundra would have been an inefficient loess trap compared to forest or even shrub tundra due to its low roughness height. The lack of abundant, full-glacial, eolian silt deposition in the loess stratigraphic record of central Alaska may be due, therefore, to a mimimal ability of the landscape to trap loess, rather than a lack of available eolian sediment. ?? 2003 University of Washington. Published by Elsevier Inc. All rights reserved.

  17. Tectonic control of Cretaceous gravity deposits and submarine Valleys in the subalpine basin, French western Alps

    SciTech Connect

    Philippe, J.; Beaudoin, B.; Fries, G.; Parize, O.

    1988-08-01

    The Late Jurassic-Early Cretaceous series of the French subalpine basin is characterized by alternating limestones and marls with numerous, thick gravity-flow deposits (carbonate debris flows and slumps, siliciclastic grain flows, turbidites). These gravity deposits originate from platforms and slopes and come through the basin via several parallel canyons and submarine valleys. Some carbonate (Berriasian) and siliciclastic (Aptian) deep-sea fans are built at the canyon mouth during intense activity of the canyons and reworking of the sediments. The tectonic control of the gravity deposits is demonstrated by the position and filling of the submarine valleys all along the Cretaceous. The submarine valleys correspond systematically to the lower part of extensional tilted blocks; the gravity deposits come along the main syn-sedimentary normal faults delimiting these tilted blocks. The gravity deposits go from one tilted block to another through some synsedimentary passes which are induced by slight folding, perhaps related to an early diapirism at some nodes of extensional faults. The canyon-like valleys are due to very strong erosion when a submarine valley cuts of the higher part of a tilted block. The gravity deposits are stacked atop each other and progressively fill the valleys. Thus the cutting and filling of the submarine valleys and canyons on occasions during the Early Cretaceous are explained by a permanent synsedimentary activity. These Jurassic and Cretaceous extensional structures are later reactivated by inversion during Tertiary compressional movements.

  18. Atmospherically deposited PBDEs, pesticides, PCBs, and PAHs in western U.S. National Park fish: concentrations and consumption guidelines.

    PubMed

    Ackerman, Luke K; Schwindt, Adam R; Simonich, Staci L Massey; Koch, Dan C; Blett, Tamara F; Schreck, Carl B; Kent, Michael L; Landers, Dixon H

    2008-04-01

    Concentrations of polybrominated diphenyl ethers (PBDEs), pesticides, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons were measured in 136 fish from 14 remote lakes in 8 western U.S. National Parks/Preserves between 2003 and 2005 and compared to human and wildlife contaminant health thresholds. A sensitive (median detection limit--18 pg/g wet weight), efficient (61% recovery at 8 ng/g), reproducible (4.1% relative standard deviation (RSD)), and accurate (7% deviation from standard reference material (SRM)) analytical method was developed and validated for these analyses. Concentrations of PCBs, hexachlorobenzene, hexachlorocyclohexanes, DDTs, and chlordanes in western U.S. fish were comparable to or lower than mountain fish recently collected from Europe, Canada, and Asia. Dieldrin and PBDE concentrations were higher than recent measurements in mountain fish and Pacific Ocean salmon. Concentrations of most contaminants in western U.S. fish were 1-6 orders of magnitude below calculated recreational fishing contaminant health thresholds. However, lake average contaminant concentrations in fish exceeded subsistence fishing cancer thresholds in 8 of 14 lakes and wildlife contaminant health thresholds for piscivorous birds in 1 of 14 lakes. These results indicate that atmospherically deposited organic contaminants can accumulate in high elevation fish, reaching concentrations relevant to human and wildlife health. PMID:18504962

  19. Atmospherically Deposited PBDEs, Pesticides, PCBs, and PAHs in Western US National Park Fish: Concentrations and Consumption Guidelines

    PubMed Central

    Ackerman, Luke K.; Schwindt, Adam R.; Simonich, Staci L.; Koch, Dan C.; Blett, Tamara F.; Schreck, Carl B.; Kent, Michael L.; Landers, Dixon H.

    2014-01-01

    Concentrations of polybrominated diphenyl ethers (PBDEs), pesticides, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons were measured in 136 fish from 14 remote lakes in 8 western US National Parks/Preserves between 2003 and 2005 and compared to human and wildlife contaminant health thresholds. A sensitive (median detection limit −18 pg/g wet weight), efficient (61% recovery at 8 ng/g), reproducible (4.1 %RSD), and accurate (7 % deviation from SRM) analytical method was developed and validated for these analyses. Concentrations of PCBs, hexachlorobenzene, hexachlorocyclohexanes, DDTs and chlordanes in western US fish were comparable to or lower than mountain fish recently collected from Europe, Canada, and Asia. Dieldrin and PBDE concentrations were higher than recent measurements in mountain fish and Pacific Ocean salmon. Concentrations of most contaminants in western US fish were 1–6 orders of magnitude below calculated recreational fishing contaminant health thresholds. However, contaminant concentrations exceeded subsistence fishing cancer screening values in 8 of 14 lakes. Average contaminant concentrations in fish exceeded wildlife contaminant health thresholds for piscivorous mammals in 5 lakes, and piscivorous birds in all 14 lakes. These results indicate that atmospherically deposited organic contaminants can accumulate in high elevation fish, reaching concentrations relevant to human and wildlife health. PMID:18504962

  20. Atmospherically deposited PBDEs, pesticides, PCBs, and PAHs in western U.S. National Park fish: Concentrations and consumption guidelines

    USGS Publications Warehouse

    Ackerman, L.K.; Schwindt, A.R.; Simonich, S.L.M.; Koch, D.C.; Blett, T.F.; Schreck, C.B.; Kent, M.L.; Landers, D.H.

    2008-01-01

    Concentrations of polybrominated diphenyl ethers (PBDEs), pesticides, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons were measured in 136 fish from 14 remote lakes in 8 western U.S. National Parks/Preserves between 2003 and 2005 and compared to human and wildlife contaminant health thresholds. A sensitive (median detection limit, -18 pg/g wet weight), efficient (61% recovery at 8 ng/g), reproducible (4.1% relative standard deviation (RSD)), and accurate (7% deviation from standard reference material (SRM)) analytical method was developed and validated for these analyses. Concentrations of PCBs, hexachlorobenzene, hexachlorocyclohexanes, DDTs, and chlordanes in western U.S. fish were comparable to or lower than mountain fish recently collected from Europe, Canada, and Asia. Dieldrin and PBDE concentrations were higher than recent measurements in mountain fish and Pacific Ocean salmon. Concentrations of most contaminants in western U.S. fish were 1-6 orders of magnitude below calculated recreational fishing contaminant health thresholds. However, lake average contaminant concentrations in fish exceeded subsistence fishing cancer thresholds in 8 of 14 lakes and wildlife contaminant health thresholds for piscivorous birds in 1of 14 lakes. These results indicate that atmospherically deposited organic contaminants can accumulate in high elevation fish, reaching concentrations relevant to human and wildlife health. ?? 2008 American Chemical Society.

  1. Use of passive samplers and surrogate surfaces to investigate sources of mercury deposited to the western United States

    NASA Astrophysics Data System (ADS)

    Wright, G.; Gustin, M. S.; Weiss-Penzias, P. S.

    2012-12-01

    The Western Airborne Contaminants Assessment Project (WACAP) showed that fish in eight National Parks of the western U.S. had mercury(Hg) concentrations that exceeded the threshold for fish eating wildlife (www.nature.nps.gov/air/Studies/air_toxics/wacap.cfm). These observations led to the development of this study focused on investigating air gaseous oxidized mercury (GOM) concentrations and potential dry deposition using developed passive samplers and surrogate surfaces. The primary question was whether local, regional or global sources are responsible for the mercury measured in fish in these Western parks. To investigate this, passive samplers and surrogate surface samplers were deployed from the coast of California to the eastern edge of Nevada. Sampling sites were located from west to east at Point Reyes National Seashore, CA; Elkhorn Slough, CA, Lick Observatory, CA; Chews Ridge, CA; Chalk Mountain, CA; Yosemite National Park, CA; Sequoia & Kings Canyon National Park, CA; and Great Basin National Park, NV. Ancillary data (meteorology and ozone concentrations) collected by the parks will be applied to better understand potential sources. Air mercury concentrations were also measured at select locations using a Tekran® 2537a/1130mercury air measurement system for 4-6 weeks. Air GOM concentrations and potential deposition were measured simultaneously as a function of elevation at Yosemite and Great Basin National Park, using the passive samplers and surrogate surfaces during sampling intensives, allowing us to better understand potential sources of mercury to park ecosystems. Data collection began in August of 2010 and was completed in June 2012. Analyses of the data thus far has shown the lowest relative concentrations and potential GOM deposition were observed at the low elevation coastal sites, Elkhorn Slough and Point Reyes National Seashore. Highest values of potential deposition were recorded at Lick Observatory, a high elevation coastal site, while

  2. [Emergy evaluation and dynamic measurement analysis of agro-ecosystems in Sichuan Province of Southwest China].

    PubMed

    Zhang, Ying-Cong; Du, Shou-Hu

    2012-03-01

    Agro-ecosystem is the most basic system for human beings survival, while the analysis of the structure and function of the system is the key to solve the problems of agro-ecological environment. In this paper, emergy theory and related economic measurement methods including data envelopment analysis, cointegration test, and error correction model were applied to quantitatively analyze the operation dynamics, environmental loading, operation efficiency, and input-output relation of the agro-ecosystems in Sichuan Province and its 21 cities in 1997-2009. In the study period, Sichuan Province was in the transition period from traditional agriculture to modern agriculture. The agricultural mechanization level of the Province improved constantly, resources utilization efficiency enhanced continually, overall structural dominant degree was better, but the over-reliance on economic emergy input caused the sustainability of the system weakened gradually. The development status of the agro-ecosystems in the Province varied among regions. Chengdu Plain and Western Sichuan Highland were either in overexploited or in underutilized, while the hilly areas were full of vitality and development potential, tended to be the important areas for the future development of Sichuan agriculture. Generally, the operation efficiency of the agro-ecosystems in the Province was relatively low, with the situation differed in different regions due to the lower technical efficiency or improper scale. There was a long-term equilibrium between the economic emergy indices and output emergy, but the short-term emergy input didn't reach the ideal output. PMID:22720632

  3. Map showing occurrences of spring-deposited travertine in the conterminous Western United States

    USGS Publications Warehouse

    Feth, J.H.; Barnes, Ivan

    1979-01-01

    Extinct travertine terraces occur hundreds of meters above present levels of spring activity and have potentials for interpretation of ancient hydrologic systems, rates of downcutting, or rates of tectonic uplift that remain virtually unexploited. The abundance and size of extinct travertine deposits suggest that in many places, such as pinnacles at the southwest end of the Searles Lake basin, California, spring activity was once more widespread and copious than it is now. Travertine of Eocene age has been reported, and a scattering of later Tertiary occurrences is known. But where age has been inferred, the inferred ages are predominantly Pleistocene or younger. So travertine seems to be a geologically transient phenomenon, subject either to removal by erosion or to burial and disappearance. Many travertine deposits are known to be on or close to faults. Their occurrence in otherwise structurally featureless alluvial valleys may, therefore, suggest the possibility of a hidden fault. From the Front Range to the Pacific, more than 300 travertime deposits have been identified. The map shows that the deposits are widely dispersed. However, there are apparent groupings on the Wasatch Fault and associated tectonic areas trending northward in Utah and southern Idaho, and also near the great fault zone that marks the eastern boundary of the Sierra Nevada, California. (Lantz-PTT)

  4. The Chahnaly low sulfidation epithermal gold deposit, western Makran volcanic arc, southeastern Iran

    USGS Publications Warehouse

    Sholeh, Ali; Rastad, Ebrahim; Huston, David L.; Gemmell, J. Bruce; Taylor, Ryan D.

    2016-01-01

    The Chahnaly Au deposit formed during the early stages of magmatism. LA-ICP-MS zircon U-Pb geochronology of host andesite and 40Ar/39Ar dating of two samples of gold-associated adularia show that the ore-stage adularia (19.83 ± 0.10 and 19.2 ± 0.5 Ma) is younger, by as much as 1.5 million years, than the volcanic host rock (20.32 ± 0.4 Ma). Therefore, either hydrothermal activity continued well after volcanism or a second magmatic event rejuvenated hydrothermal activity. This second magmatic event may be related to eruption of porphyritic andesite at ~20.32 ± 0.40 Ma, which is within error of ~19.83 ± 0.10 Ma adularia. The new LA-ICP-MS zircon U-Pb host rock and vein adularia 40Ar/39Ar ages suggest that early Miocene magmatism and mineralization in the Bazman area is of a similar age to that of the Saindak porphyry and Tanjeel porphyry center of the giant Reko Diq deposit. This confirms the existence of early Miocene arc magmatism and mineralization along the Iranian part of the Makran volcanic arc. Ore, alteration mineralogy, and alteration patterns indicate that the Chahnaly deposit is a typical low-sulfidation epithermal Au deposit, located in a poorly explored part of the Makran volcanic arc in Iran.                   

  5. Combined effect of tectonism, eustasy, and sediment supply on the depositional-sequence history of the western offshore, South Africa

    SciTech Connect

    Jungslager, E.H.A. )

    1991-03-01

    Interpreted seismic profiles and maps of depositional systems tracts highlight variations in basin-fill architecture and their inferred causes along western offshore South Africa. Sequence-stratigraphic concepts developed by Exxon were used to interpret 10,000 km of seismic data and logs from 31 exploration boreholes within an area of 90,000 km{sup 2}. Lower frequency second-order supercycles (5-10 Ma) are attributed to changes in the rate of subsidence and are expressed either by predominantly progradational or aggradational depositional supersequence. In addition to these long-duration, basin-wide stratigraphic packages, component depositional sequences that formed in response to third order (1-5 Ma) and higher frequency cycles vary with structural setting within the depobasin, namely depocenter, basin flanks, shelf-edge, and slope systems. High-order sequences are attributed to eustatically driven, high-frequency, base-level changes and/or localized tectonic events (i.e. slope failure, gravity faulting). Variations in the areal distribution of lowstand and shelf-margin systems tracts document lateral shifting sediment supplies and the presence of entrenched feeder-canyons linked to incised valley systems on the shelf. Many canyons, however, terminate updip and may be related to slope failure and headward erosion. The tentative correlation of regionally developed unconformities of the west coast based on microfaunal dating of a limited number of marine condensed sections points to a remarkable correspondence with the Exxon global sea-level chart.

  6. Precipitation source inferred from stable isotopic composition of Pleistocene groundwater and carbonate deposits in the western desert of Egypt.

    SciTech Connect

    Sultan, M.; Sturchio, N.; Hassan, F. A.; Abdel, M.; Hamdan, R.; Mahmood, A. M.; Alfy, Z. E.; Stein, T.; Environmental Research; Univ. Coll. London; Cairo Univ.; Ain Shams Univ.; Egyptian Geological survey and Mining Authority; Washington Univ.

    1997-01-01

    An Atlantic source of precipitation can be inferred from stable isotopic data (H and O) for fossil groundwaters and uranium-series-dated carbonate spring deposits from oases in the Western Desert of Egypt. In the context of available stable isotopic data for fossil groundwaters throughout North Africa, the observed isotopic depletions ({delta}D -72 to -81{per_thousand}; {delta}{sup 18}O -10.6 to -11.5{per_thousand}) of fossil ({ge}32,000 yr B.P.) groundwaters from the Nubian aquifer are best explained by progressive condensation of water vapor from paleowesterly wet oceanic air masses that traveled across North Africa and operated at least as far back as 450,000 yr before the present. The values of {delta}{sup 18}O (17.1 to 25.9{per_thousand}) for 45,000- to >450,000-yr-old tufas and vein-filling calcite deposits from the Kharga and Farafra Oases are consistent with deposition from groundwaters having oxygen isotopic compositions similar to those of fossil groundwaters sampled recently at these locations.

  7. Control on the erosional and depositional dynamics inferred from grain size variation along the Pisco river, Western Peru.

    NASA Astrophysics Data System (ADS)

    Camille, Litty; Robert, Duller; Fritz, Schlunegger

    2015-04-01

    The Pisco Valley situated on the western side of the Andes represents an ideal laboratory for exploring potential controls on the accumulation and subsequent erosion of sediment because it hosts several well-preserved cut-and-fill terrace sequences. In this study we infer that a climatic change in combination with eustatic sea level drop have been the main drivers of erosion of the valley flanks and subsequent sedimentation of the Quaternary terrace deposits. We mostly focused on the sediments of the well preserved 40 ka-old terrace level (Minchin pluvial period) and compare them with the modern bed material to explore relationships between longitudinal and temporal variations of grain size downstream fining, water budgets and sediment transport dynamics recorded by the modern and the terrace deposits. To this extent, grain size data were collected from digital images taken at five different sites along the channel. We measured the b-axis of the particles on digital images, which yielded in a total of ca. 2500 grain size measurements per site for the modern material and ca. 4000 per site for the terrace deposits. The results reveal a higher downstream fining rate for the modern material than for the terrace deposits for the D50 and D84 but the inverse for the D96. For the modern sediments, the fining rate is 0.7 mm/km for the D50 while the equivalent percentile of the terrace deposits has a lower fining rate of 0.3 mm/km. The modern deposits are better sorted and have finer grains than the ancient sediments. The results of hydrological calculations suggest that the water discharge required to transport the D50 of the Pisco River during modern and Minchin times and to evacuate the supplied material has been nearly identical whereas the water discharge required to transport supplied material is higher during the Minchin time than today if the D96 is taken as threshold value. We propose a scenario where eustatic sea level drop initiated the beginning of the

  8. Morphology and geology of an interior layered deposit in the western Tithonium Chasma, Mars

    NASA Astrophysics Data System (ADS)

    Baioni, Davide

    2013-12-01

    This paper describes a morphologic and morphometric survey of a 3.1 km-high, domeshaped upland in western Tithonium Chasma (TC) which coincides with areas containing abundant surface signatures of the sulphate mineral kiersite, as identified by the OMEGA image spectrometer. The morphologic features of the dome were investigated through an integrated analysis of the available Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment (HiRISE), Mars Orbiter Camera, and Context Camera data, while the morphometric characteristics of the structure were measured using a topographic map (25-m contour interval) built from high-resolution stereo camera (HRSC) and Mars Orbiter Laser Altimeter (MOLA) data.

  9. Black Carbon Deposition on Glaciers and in the Seasonal Snowpack in Western Washington's Mountainous Regions

    NASA Astrophysics Data System (ADS)

    Delaney, I.; Kaspari, S.; Larrabee, M.

    2012-12-01

    Black carbon deposition on snow and ice darkens the surface of glaciers and snowpack, reducing albedo. Radiation absorbed by black carbon in snow can accelerate snowmelt and change the timing of runoff. This is particularly important in Washington State, as glaciers and seasonal snowpack have shrunk considerably in recent years and are integral to the region's water resources. However, little data exists regarding the concentration of black carbon in Washington snow, which is necessary to determine if enough black carbon is present to substantially accelerate snowmelt. From the winter through the summer of 2012, we collected snow samples from the snow surface, snow pits and snow cores (< 5 m depth, in many cases capturing the entire annual snowpack). Study sites include the Nisqually and Emmons glaciers on Mt. Rainier, Blewett Pass in the central Cascades, N. Klawatti, Noisy and Sandalee glaciers in the North Cascades and Blue Glacier on Mt. Olympus. Samples were analyzed for black carbon using a Single Particle Soot Photometer (SP2), and select samples were also analyzed for black carbon using a Sunset Lab OC-EC Aerosol Analyzer to compare with the SP2 method. We use the resultant data set to examine how snow accumulation, dry deposition, and proximity to emission sources (such as the Puget Sound metropolitan area) affect black carbon concentration in snow and ice. The results of this research provide insight in to 1) regional scale variation in black carbon deposition, 2) temporal trends in black carbon deposition, and 3) the persistence of black carbon in the snowpack throughout the season.

  10. Effects of African dust deposition on phytoplankton in the western tropical Atlantic Ocean off Barbados

    NASA Astrophysics Data System (ADS)

    Chien, Chia-Te; Mackey, Katherine R. M.; Dutkiewicz, Stephanie; Mahowald, Natalie M.; Prospero, Joseph M.; Paytan, Adina

    2016-05-01

    Bioassay incubation experiments conducted with nutrients and local atmospheric aerosol amendments indicate that phosphorus (P) availability limited phytoplankton growth in the low-nutrient low-chlorophyll (LNLC) ocean off Barbados. Atmospheric deposition provides a relatively large influx of new nutrients and trace metals to the surface ocean in this region in comparison to other nutrient sources. However, the impact on native phytoplankton is muted due to the high ratio of nitrogen (N) to P (NO3:SRP > 40) and the low P solubility of these aerosols. Atmospheric deposition induces P limitation in this LNLC region by adding more N and iron (Fe) relative to P. This favors the growth of Prochlorococcus, a genus characterized by low P requirements and highly efficient P acquisition mechanisms. A global three-dimensional marine ecosystem model that includes species-specific phytoplankton elemental quotas/stoichiometry and the atmospheric deposition of N, P, and Fe supports this conclusion. Future increases in aerosol N loading may therefore influence phytoplankton community structure in other LNLC areas, thereby affecting the biological pump and associated carbon sequestration.

  11. Mineralogy and sedimentology of the Miocene Göcenoluk borate deposit, Kırka district, western Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    García-Veigas, Javier; Helvacı, Cahit

    2013-05-01

    The Miocene boratiferous district of Kırka, in western Anatolia (Turkey), is the most important Na-borate (borax) resource in the world. Two separate deposits in the Kırka district are located near the villages of Sarıkaya and Göcenoluk (Eskişehir Province). Borax is intensively exploited in open-pit mines in the Sarıkaya deposit while only small quarries of colemanite are known in the Göcenoluk deposit. Recent exploratory drilling in the Göcenoluk area intersected a thick succession of dolostones, tuffs and three borate-bearing units (Lower, Intermediate and Upper Borate Units). In them, the most abundant borate mineral is ulexite (Ca-Na-borate) passing at depth to probertite. Borax (Na-borate) is only present in the Intermediate Borate Unit. Minor amounts of colemanite (Ca-borate) and hydroboracite (Ca-Mg-borate) occur at the base, and/or top, of each mineralized unit. Pyroclastic layers within the borate units show intense alteration by alkaline, boron-bearing waters and formation of diagenetic clay minerals (smectites), zeolites (analcime) and borosilicates (searlesite). The Göcenoluk succession is interpreted as a shallow, ephemeral, alkaline lake deposit in which carbonates formed as stromatolites and travertines. Borate precipitation in the Göcenoluk area took place interstitially within muddy and carbonate sediments in a lateral progression from marginal Ca-borates towards Na-Ca-borates and rarely to Na-borates in the center of the lake. Authigenic silicate mineral distribution shows parallel changes toward the center of the lake that reflect increasing pH gradient.

  12. Eolian depositional phases during the past 50 ka and inferred climate variability for the Pampean Sand Sea, western Pampas, Argentina

    NASA Astrophysics Data System (ADS)

    Tripaldi, Alfonsina; Forman, Steven L.

    2016-05-01

    The Pampean Sand Sea, which occurs from the Argentinian Pampas to the eastern Andean piedmont, hosts presently stabilized dune fields spanning the late Quaternary. This study integrates previous results and presents new geomorphic, stratigraphic, sedimentological, and chronologic data for nineteen >2 m-thick eolian successions for the San Luis paleo-dune field, western Pampas, to better constrain the depositional history. Six eolian depositional phases are identified spanning the past 50 ka, interposed with paleosols and/or bounded by erosive surfaces. Age control was from 61 OSL ages of small aliquots of quartz grains from eolian stratigraphic units. The inferred timing of eolian phases are at ca. 70 ± 10 yr, 190 ± 20 yr, 12 to 1 ka, 22 to 17 ka, 29 to 24 ka, and 40 to 32 ka. A maximum span for periods of pedogenesis at ca. 12 to 17 ka, 22 to 24 ka, and 29 to 32 ka was provided by bounding OSL ages, which broadly overlap with high stands of pluvial lakes and glacier advances in the central Andes. We infer that the added precipitation may reflect expansion of the Southern Hemisphere monsoon, associated with Northern Hemisphere Heinrich events, leading to episodes of significantly wetter conditions (>350 mm MAP) to at least 35° S. Most of the Holocene (12 ka to 0.8 ka) was characterized by sand sheet deposit under drier than present conditions (100-450 mm MAP), associated with Monte-type vegetation (shrub steppe). The latest two eolian depositional phases, occurred at ca. 190 and 70 yr ago, during the historic period with European settlement and are related to anthropogenic landscape disturbance, though the youngest phase was concomitant with 1930s drought. Wet conditions dominated since ca. AD 1970 with new lakes and rivers forming across this eolian terrain; an incongruous environmental response in reference to drier conditions for most of the Holocene.

  13. Depositional patterns and hydrocarbon occurrence in middle to upper Miocene strata in part of the western Niger Delta Basin, Nigeria

    NASA Astrophysics Data System (ADS)

    Agyingi, C. M.; Agagu, O. K.; Fozao, K. F.; Njoh, O. A.; Ngalla, N.

    2013-04-01

    The relation of depositional patterns to hydrocarbon occurrence in middle to upper Miocene strata of part of the western Niger Delta Basin is postulated from the study of electrical logs, radiometric logs, lithologic logs, bottom hole temperatures, intervals of hydrocarbon occurrence and paleontological data. Alternating sands and shales of the Agbada Formation were deposited in the area (up to 720 m, middle Miocene and 510 m, upper Miocene) mainly as regressive off lap sequences in a paralic environment with depo-centers located in the south of the study area. Three deltaic facies can be recognized based on the relative amounts of shale and sand including, proximal delta front facies (>70% sand), distal delta front facies (30-70% sand) and prodelta facies (<30% sand). The upper Miocene is generally sandier than the middle Miocene as a result of south-westerly progradation of delta front facies from middle to upper Miocene. Geothermal gradients in the area range from 2.5 °C/100 m to 4.4 °C/100 m. Isothermal maps show that some middle to upper Miocene shales could have undergone catagenesis to become mature source rocks. Three depositional zones (A, B, C) corresponding to dominant depositional facies i.e., proximal delta, distal delta and prodelta respectively, have been delineated from sand percentage maps. There is a progression of these zones from A through B to C in a generally south-westerly direction (the direction of delta progradation). Data for hydrocarbon intervals reveal the predominance of hydrocarbons in Zone C due to high entrapment potentials and to a lesser extent in Zone B. Zone A is barren as a result of poor entrapment potentials. The juxtaposition of distal delta front sands and prodelta mud could have initiated growth faults which constitute the major types of traps in the basin.

  14. Frozen subduction in the Yangtze block: insights from the deep seismic profiling and gravity anomaly in east Sichuan fold belt

    NASA Astrophysics Data System (ADS)

    Xiong, Xiaosong; Gao, Rui; Wang, Haiyan; Zhang, Jisheng; Guo, Lianghui

    2016-04-01

    The Sichuan basin is the main part of the middle-upper Yangtze block, which has been experienced a long-term tectonic evolution since Archean. The Yangtze block was regarded as a stable block until the collision with the Cathaysia block in late Neoproterozoic. A new deep seismic reflection profile conducted in the eastern Sichuan fold belt (ESFB) discovered a serials of south-dipping reflectors shown from lower crust to the mantle imply a frozen subduction zone within the Yangtze block. In order to prove the speculation, we also obtain the middle-lower crustal gravity anomalies by removing the gravity anomalies induced by the sedimentary rocks and the mantle beneath the Moho, which shows the mid-lower crustal structure of the Sichuan basin can be divided into eastern and western parts. Combined with the geochronology and Aeromagnetic anomalies, we speculated the Yangtze block was amalgamated by the West Sichuan and East Sichuan blocks separated by the Huayin-Chongqing line. The frozen subduction zone subsequently shifted to a shear zone accommodated the lower crustal shortening when the decollement at the base of the Nanhua system functioned in the upper plate.

  15. Mineral-petrographic features of hydrocarbon reservoirs of the Tevlinsko-Russkinskoe oil deposit (Western Siberia)

    NASA Astrophysics Data System (ADS)

    Sitdikova, Elina; Izotov, Victor

    2010-05-01

    The Tevlinsko-Russkinskoe oil field is located in the central part of the West Siberian lowland. It concerns a group of multistory deposits and is one of the perspective deposits in the West Siberian oil and gas province. The young Sortym formation and the Jurassic sediments offer the best prospects. Layers are consisted of sand-clay deposits of Mesozoic-Cainozoic sedimentary cover and rocks of the pre-Jurassic basement. Core material of base drill holes of the Tevlinsko-Russkinskoe oil field was studied in order to obtain detailed lithological and mineralogical characteristics of rocks features. These drill holes found out main productive horizons. Sandstones of productive horizons of Jurassic petroliferous complex are of a homogeneous and monotonous structure. In the studied samples of core material massive structures prevail. Mineral composite of clastic component of sandstones is polymictic and it is represented by quartz, orthoclase, microcline, plagioclases, biotite, strongly changed dark-coloured minerals, fragments of effusive rocks and quartzite of different degrees of recrystallization. Cluster formation - grains accretion into separated quartzite-like parts - is typical for these rocks. Process of cluster formation is accompanied by change of sandstone structure. This results in reservoir quality alteration and extension of porosity and permeability properties. In the studied rocks-reservoirs of Jurassic oil complex processes of cluster formation were lasting during period of diagenesis and were followed by repartition of cement mass. We carried out electron microscopic research of reservoirs structure to analyze void space structure. Electron microscopic studies were spent on the scanning electron microscope of XL-30 system (Phillips company). The conducted research testifies that reservoirs can be considered a mesoporous-nanoporous medium. Its' studying is of a great importance for realization of questions of Tevlinsko-Russkinskoe oil field working out.

  16. A quantitative micropaleontologic method for shallow marine peleoclimatology: Application to Pliocene deposits of the western North Atlantic Ocean

    USGS Publications Warehouse

    Cronin, T. M.; Dowsett, H.J.

    1990-01-01

    A transfer function was developed to estimate summer and winter paleotemperatures for arctic to tropical regions of the western North Atlantic Ocean using fossil ostracode assemblages. Q-mode factor analysis was run on ostracode assemblages from 100 modern bottom sediment samples from continental shelves of North America, Greenland and the Caribbean using 59 ostracode taxa. Seven factors accounting for 80% of the variance define assemblages that correspond to frigid, subfrigid, cold temperate, mild temperate, warm temperate, subtropical and tropical climatic zones. Multiple regression of the factor matrix against observed February and August bottom temperatures yielded an astracode transfer function with an accuracy of about ??2??C. The transfer function was used to reconstruct middle Pliocene (3.5-3.0 Ma) shallow marine climates of the western North Atlantic during the marine transgression that deposited the Yorktown Formation (Virginia and North Carolina), the Duplin Formation (South and North Carolina) and the Pinecrest beds (Florida). Middle Pliocene paleowater temperatures in Virginia averaged 19??C in August and 13.5??C in February, about 5??C to 8??C warmer than at comparable depths off Virginia today. August and February water temperatures in North Carolina were 23??C and 13.4??C, in South Carolina about 23??C and 13.5??C and in southern Florida about 24.6??C and 15.4??C. Marine climates north of 35??N were warmer than today; south of 35??N, they were about the same or slightly cooler. Thermal gradients along the coast were generally not as steep as they are today. The North Atlantic transfer function can be applied to other shallow marine Pliocene and Pleistocene deposits of eastern North America. ?? 1990 Elsevier Science Publishers B.V.

  17. The Paddy's Flat Gold District (Murchison, Western Australia), insight on a rheologically and structurally control lode gold deposit

    NASA Astrophysics Data System (ADS)

    Thebaud, N.; Hollingsworth, D.; Gonzalez-Alvarez, I.

    2007-12-01

    In the North-West of the world class gold producer Yilgarn craton lies the Murchison Goldfield (Western Australia). Several rich deposits mined since the turn of the 19th century suggest that this late-Archaean terrane is highly prospective for gold exploration. Located in the northern part of the Murchison goldfield, the Paddy's Flat District recorded a production of ~2 Moz. The Paddy's Flat Gold District area is located on an N-S trending, steeply east dipping shear on the north western limb of an upright isoclinal fold known as the Polelle syncline. It is hosted in a strained and metamorphosed volcanic and minor sedimentary sequence. Mineralisation within the Paddy's Flat District is not limited to a particular rock type and it is associated with a wide range of lithologies including: (i) intermediate to felsic extrusive volcanics, (ii) intrusive porphyrytic microgranite, (iii) ultramafic volcanic assemblage and (iv) iron rich banded chert. Instead, the mineralisation is highly structurally controled by the Paddy's Flat shear zone which provided fluid-pathways for the mineralising fluid. Regardless of the lithological composition, the mineral assemblage associated with the gold mineralisation consists of quartz, carbonate (ankerite, siderite), sulphides (pyrite, arsenopyrite), fuchsite and sericite assemblage suggesting the introduction of an oxidizing fluid rich in Au, S, As and K ± SiO2. At Paddys Flat the mineralisation is spatially associated with rheologicaly competent units or with domains located at the boundary between rheologically distinct lithologies within the main shear. The fluid pathways provided by the shear zone and the rheological contrast are suggested to be key parameters in the formation of economic lode gold deposit in the Paddy's Flat district.

  18. Cretaceous combined structure in eastern Sichuan Basin, China

    NASA Astrophysics Data System (ADS)

    Wang, P.; Liu, S.

    2009-12-01

    Eastern Sichuan Basin is confined by two thin-skinned fold-thrust belt, NW-trending Southern Daba Shan (Shan=Mountain) (SDB) in the northeast and NNE- or NE-trending Western XueFeng Shan (WXF) in the southeast, which constitute two convergent salients convex to the inner basin respectively. Although many factors can lead to the formation of fold-thrust belt salients, the eastern Sichuan salients would be attributed to the combined structure (firstly nominated by Chinese geologist, Li Siguang), which means the interaction of two structural belts in the same period. By field surveying and geological map interpreting, we found that WXF deformation began in Late Jurassic along the eastern side of structral belt, where the synclines cored by Upper-Middle Jurassic rock. The initial time of SDB deformation remains poorly determined, however our palaeocurrent data of Lower Cretaceous rock in adjecent foreland basin indicate the provenance from northeast or east. Hence we considered the two fold-thrust belt started interactive in Late Jurassic and mainly combined during Cretaceous. In Early Cretaceous, the front belt of WXF salient arrived near KaiXian where NEE-trending arc-shape folds converged with the NWW-trending arc-shape folds of SDB.The two salients shaped like an westward "open mouth", east of which EW-trending folds of two structural belts juxtaposed. Particularly in the middle belt of WXF (FengJie - WuFeng) the earlier NEE-trending folds were refolded by later NNE-trending folds. We interpret the NEE-trending folds as the front belt of earlier (maybe Late Jurassic) WXF salient. When the two combined fold belts propagated westward together, the original NNE-trending front belt of WXF constrained by the front belt of SDB and formed the curved fold trend lines convex to NNW. Then as WXF deformation continued but SDB gradually terminated, the consequent NNE-trending folds could not be curved and would superpose on the earlier NEE-trending folds.In Late Cretaceous

  19. Miocene and early Pliocene epithermal gold-silver deposits in the northern Great Basin, western United States: Characteristics, distribution, and relationship to Magmatism

    USGS Publications Warehouse

    John, D.A.

    2001-01-01

    Numerous important Miocene and early Pliocene epithermal Au-Ag deposits are present in the northern Great Basin. Most deposits are spatially and temporally related to two magmatic assemblages: bimodal basalt-rhyolite and western andesite. These magmatic assemblages are petrogenetic suites that reflect variations in tectonic environment of magma generation. The bimodal assemblage is a K-rich tholeiitic series formed during continental rifting. Rocks in the bimodal assemblage consist mostly of basalt to andesite and rhyolite compositions that generally contain anhydrous and reduced mineral assemblages (e.g., quartz + fayalite rhyolites). Eruptive forms include mafic lava flows, dikes, cinder and/or spatter cones, shield volcanoes, silicic flows, domes, and ash-flow calderas. Fe-Ti oxide barometry indicates oxygen fugacities between the magnetite-wustite and fayalite-magnetite-quartz oxygen buffers for this magmatic assemblage. The western andesite assemblage is a high K calc-alkaline series that formed a continental-margin are related to subduction of oceanic crust beneath the western coast of North America. In the northern Great Basin, most of the western andesite assemblage was erupted in the Walker Lane belt, a zone of transtension and strike-slip faulting. The western andesite assemblage consists of stratovolcanoes, dome fields, and subvolcanic plutons, mostly of andesite and dacite composition. Biotite and hornblende phenocrysts are abundant in these rocks. Oxygen fugacities of the western andesite assemblage magmas were between the nickel-nickel oxide and hematite-magnetite buffers, about two to four orders of magnitude greater than magmas of the bimodal assemblage. Numerous low-sulfidation Au-Ag deposits in the bimodal assemblage include deposits in the Midas (Ken Snyder), Sleeper, DeLamar, Mule Canyon, Buckhorn, National, Hog Ranch, Ivanhoe, and Jarbidge districts; high-sulfidation gold and porphyry copper-gold deposits are absent. Both high- and low

  20. Early Depositional History of the Eocene Izu-Bonin Mariana Arc, Western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Waldman, R.; Marsaglia, K. M.; Tepley, F. J., III

    2015-12-01

    Expedition 351 of the International Ocean Discovery Program cored an Eocene section at Site U1438 in the Philippine Sea that provides insight into the early history of the Izu-Bonin arc. Subduction here is hypothesized to have initiated spontaneously, leaving a characteristic depositional sequence of post-subduction-initiation localized extension and volcanism. We conducted detailed macroscopic and microscopic study of the cores of the lowermost 100m of volcaniclastic and sedimentary rocks (Unit IV) directly overlying subduction initiation igneous basement, to identify depositional facies and trends. We subdivided Unit IV into three subunits based on lithologic characteristics. Transitions between the subunits are relatively abrupt, occurring within the length of a single core. The lowermost subunit (IVA) consists of 4 meters of laminated pelagic claystone with thin beds of graded volcaniclastic siltstone, and fine-grained tuff laminae composed of plagioclase feldspar and green-brown amphibole. The middle subunit (IVB) comprises 51 meters of texturally variable, thick-bedded, coarse-grained gravity flow deposits. These are composed of volcaniclastic sandstone and conglomerate containing glassy and tachylitic volcanic grains as well as sedimentary lithic fragments, along with traces of shallow-water carbonate bioclasts. Subunit IVB sediments are poorer in feldspar than IVA and contain only trace amphibole. They show variable grain rounding and an upsection increase in vitric components. Tachylite grains range from sub-angular to well rounded throughout, and other volcanic grain types show upward increases in angularity and vesicularity. The abrupt transition from pelagic sediments in subunit IVA to shallow-water-sourced gravity flows in subunit IVB suggests a rapid emergence of shallow-water to subaerial volcanic center early in the arc's development. The upper part of subunit IVB also contains igneous intrusions, providing possible evidence for more proximal

  1. Diagenesis of upper Devonian platform deposits in Emanual Range, Canning basin, western Australia

    SciTech Connect

    Pedone, V.A.; Meyers, W.J.

    1988-02-01

    The Emanuel Range consists of 600 m of peritidal and subtidal carbonate platform deposits of the Pillara Limestone (Givetian-lower Frasnian). Diagenesis of the lower 75 m contrasts markedly with the upper 520 m, principally in the occurrence of extensive dolomite. Formation of extensive secondary porosity by tectonic fracturing, in-situ brecciation, and dissolution of calcitic fossils was enhanced in previously dolomitized strata, exhibiting only minor occurrences in nondolomitized rocks. Formation of secondary porosity occurred over an extended period, marked by a succession of calcite cements, generally following a sequence from slightly ferroan, luminescently zoned cements to nonferroan, nonluminescent cement. Beckite chalcedony and hematite/goethite postdate but are associated with the final calcite cement. The post-dolomite diagenetic sequence suggests initial cementation under reducing burial conditions to final cementation under strongly oxidizing conditions. Fluids moving through the extensive Late carboniferous karst system in the platform may be the diagenetic agent for the later calcites, chalcedony, and iron oxides.

  2. Stratigraphy and reservoir quality of the turbidite deposits, western sag, Bohai bay, China P.R.

    NASA Astrophysics Data System (ADS)

    Rotimi, Oluwatosin J.; Ako, Bankole D.; Zhenli, Wang

    2014-11-01

    Stratigraphic and subtle reservoirs such as pinchouts, sand lenses and unconformities have been discovered in Bohai basin. These reservoirs occur in sub-basins and sag structures called depressions. A prolific depression is the Liaohe depression that has been filled with rapidly changing mixed alluvial fan deposit of the Cenozoic age. Attempts made at recovering residual hydrocarbon from the subtle reservoir have necessitated the re-evaluation of available data to characterize and model the prolific Shahejie Formation turbidite deposit occurring as pinchouts and sand lenses for hydrocarbon assessment, reservoir quality and possible recovery through enhanced methods. Methods employed covered well logs analysis, clustering analysis for electrofacies and fuzzy logic analysis to predict missing log sections. Stratigraphic and structural analysis was done on SEGY 3D seismic volume after seismic to well tie. Stochastic simulation was done on both discrete and continuous upscaled data. This made it possible to correctly locate and laterally track identified reservoir formation on seismic data. Petrophysical parameters such as porosity and permeability were modeled with result of clustering analysis. Result shows that electrofacies converged on 2 rock classes. The area is characterized by the presence of interbeded sand-shale blanket formations serving as reservoir and seal bodies. The reservoir quality of the formations as seen on the petrophysical analysis done is replicated in simulation volume results. Reservoir rocks have porosity between 0.1 and 0.25, permeability between 1 and 2mD and hydrocarbon saturation as high as 89%. Lithofacies are observed to be laterally inconsistent, sub-parallel to dipping and occurring as porous and permeable continuous beds or pinchouts hosting hydrocarbon. The stochastic stratigraphic model depicts rock units in associations that are synsedimentary. The prevalent configuration gotten from the model gave an insight into exploring and

  3. Palynostratigraphy and depositional environment of Vastan Lignite Mine (Early Eocene), Gujarat, western India

    NASA Astrophysics Data System (ADS)

    Rao, M. R.; Sahni, Ashok; Rana, R. S.; Verma, Poonam

    2013-04-01

    Early Eocene sedimentary successions of south Asia, are marked by the development of extensive fossil-bearing, lignite-rich sediments prior to the collision of India with Asia and provide data on contemporary equatorial faunal and vegetational assemblages. One such productive locality in western India is the Vastan Lignite Mine representing approximately a 54-52 Ma sequence dated by the presence of benthic zone marker species, Nummulites burdigalensis burdigalensis. The present study on Vastan Lignite Mine succession is based on the spore-pollen and dinoflagellate cyst assemblages and documents contemporary vegetational changes. 86 genera and 105 species belonging to algal remains (including dinoflagellate cysts), fungal remains, pteridophytic spores and angiospermous pollen grains have been recorded. On the basis of first appearance, acme and decline of palynotaxa, three cenozones have been recognized and broadly reflect changing palaeodepositional environments. These are in ascending stratigraphic order (i) Proxapertites Spp. Cenozone, (ii) Operculodinium centrocarpum Cenozone and (iii) Spinizonocolpites Spp. Cenozone. The basal sequence is lagoonal, palm-dominated and overlain by more open marine conditions with dinoflagellate cysts and at the top, mangrove elements are dominant. The succession has also provided a unique record of fish, lizards, snakes, and mammals.

  4. Mass transport deposits as witness of Holocene seismic activity on the Ligurian margin, Western Mediterranean (ASTARTE project)

    NASA Astrophysics Data System (ADS)

    Samalens, Kevin; Cattaneo, Antonio; Migeon, Sébastien

    2016-04-01

    The Ligurian Margin (Western Mediterranean) is at the transition between the Southern Alpes and the Liguro-Provençal margin and it is one of the most seismic areas of France. Several historic earthquakes have been indexed; the strongest, on February 23rd, 1887, occurred offshore Menton and Imperia and also caused a tsunami wave. Its equivalent magnitude has been estimated between 6 and 6.5. In addition, a moderate recurrent seismicity shakes the margin. The aim of this study is to understand the link between seismic activity and slope destabilization, and to identify the sedimentary deposits resulting from mass transport or turbidity currents. During Malisar (Geoazur laboratory), Prisme 2 and Prisme 3 (Ifremer) cruises, bathymetry, seafloor imagery (SAR), geophysics data (CHIRP SYSIF and high resolution seismics), and sediment cores have been acquired on the continental slope, focussing on canyons and submarine landslides, and in the basin. These data record numerous mass transport deposits (slump, debrites) in the different physiographic areas of the margin. To search for evidences of past Ligurian margin seismicity during the Holocene, we focused on the northeast part of the margin, the Finale area. We identified and sampled acoustically transparent Mass Transport Deposits up to 20-m thick in the bottom of three coaleshing canyons: Noli, Pora and Centa canyons from W to E in the area offshore Finale Ligure. We also recovered an MTD in the collecting deeper canyon system. MTDs in cores appear as sediment with different degrees of deformation (tilted blocks, slump, debrites) and are topped by hemipelagites. The radiocarbon age of the top of MTDs can be considered synchronous and centered around 4900 yr BP. Mass wasting occurring over more than 50 km of the Ligurian margin could indicate that an earthquake stroke the Finale area sector at that time.

  5. The Bi'r Tawilah deposit, central western Saudi Arabia: Supergene enrichment of a Pan-African epithermal gold mineralization

    NASA Astrophysics Data System (ADS)

    Surour, Adel A.; Harbi, Hesham M.; Ahmed, Ahmed H.

    2014-01-01

    The Bi'r Tawilah gold deposit in central western Saudi Arabia represents a Pan-African example of gold mineralization in which both hypogene and supergene ores are recorded. The sulphidic gold ore is hosted in intermediate to felsic intrusions that occur along the N-S trending thrust-fault zone within the so-called “Nabitah orogenic zone”. There are four rock units present (from oldest to youngest): serpentinites and related listwaenites, diorites, granitic rocks and porphyries. Hydrothermal alteration consists of chloritization, sericitization, carbonatization and silicification and affects all rock types. Chloritization of biotite results in abundant rutile, whereas sulphidization coincides with carbonatization. The Bi'r Tawilah ore is confined to NW-trending shears (Riedel fractures) related to N-S slip of the pre-existing Tawilah thrust due to activation within the Najd fault system. Samples from the boreholes show macro- and microscopic evidence of shearing such as micro-shear planes and strain shadows of pyrite. Sulphides and gold are present in most rock types. Paragenetically, the sulphides consist of abundant pyrite and relatively lesser amounts of arsenopyrite, in addition to very minor chalcopyrite, sphalerite and galena. In all boreholes, it was noticed that the abundance of arsenopyrite increases with depth. The elevated silver content of electrum (∼13-22 wt%) at Bi'r Tawilah is typical of gold deposits and low-sulphidation epithermal deposits. The early mineralization stage took place in proximity to hydrothermally altered intermediate to felsic intrusions. The aerially restricted hydrothermal alteration by carbon-aqueous fluids led to ore remobilization in which gold amounts up to 4.3 g/t. Finally, gold enrichment (up to 5.4 g/t) resulted from supergene alteration that took place during weathering above the water table at a depth of ∼20-25 m.

  6. Invisible gold in arsenian pyrite and arsenopyrite from a multistage Archaean gold deposit: Sunrise Dam, Eastern Goldfields Province, Western Australia

    NASA Astrophysics Data System (ADS)

    Sung, Y.-H.; Brugger, J.; Ciobanu, C. L.; Pring, A.; Skinner, W.; Nugus, M.

    2009-10-01

    The Sunrise Dam gold mine (11.1 Moz Au) is the largest deposit in the Archaean Laverton Greenstone Belt (Eastern Goldfields Province, Yilgarn Craton, Western Australia). The deposit is characterized by multiple events of fluid flow leading to repeated alteration and mineralization next to a major crustal-scale structure. The Au content of arsenian pyrite and arsenopyrite from four mineralizing stages (D1, D3, D4a, and D4b) and from different structural and lithostratigraphic environments was measured using in situ laser ablation inductively coupled plasma mass spectrometry. Pyrite contains up to 3,067 ppm Au ( n = 224), whereas arsenopyrite contains up to 5,767 ppm ( n = 19). Gold in arsenopyrite (D4a stage) was coprecipitated and remained as “invisible gold” (nanoparticles and/or lattice-bound) during subsequent deformation events. In contrast, gold in pyrite is present not only as “invisible gold” but also as micrometer-size inclusions of native gold, electrum, and Au(Ag)-tellurides. Pristine D1 and D3 arsenian pyrite contains relatively low Au concentrations (≤26 ppm). The highest Au concentrations occur in D4a arsenian-rich pyrite that has recrystallized from D3 pyrite. Textures show that this recrystallization proceeded via a coupled dissolution-reprecipitation process, and this process may have contributed to upgrading Au grades during D4a. In contrast, Au in D4b pyrite shows grain-scale redistribution of “invisible” gold resulting in the formation of micrometer-scale inclusions of Au minerals. The speciation of Au at Sunrise Dam and the exceptional size of the deposit at province scale result from multiple fluid flow and multiple Au-precipitating mechanisms within a single plumbing system.

  7. Geologic history and palynologic dating of Paleocene deposits, western Rock Springs uplift, Sweetwater County, Wyoming

    USGS Publications Warehouse

    Kirschbaum, M.A.; Nelson, S.N.

    1988-01-01

    During the latest Cretaceous or earliest Paleocene, a northwest-southeast trending anticline developed in the area of the present Rock springs uplift in southwestern Wyoming. This ancestral structure was eroded to a surface of fairly low relief on which a paleosol developed. The surface was formed on the Upper Cretaceous Almond Formation throughout the study area. In the early middle Paleocene (P3 palynomorph zone), topographic lows on the erosion surface were infilled by alluvial deposits that accumulated in channel, floodplain, and backswamp environments. An organic-rich facies contains numerous coal beds and is middle to late Paleocene in age (P3 to P5 zones). The assemblage of pollen that defines the late middle Paleocene (P4 zone) is absent from the area suggesting a hiatus, although no lithologic break was observed at this boundary. The younger organic-poor facies begins in the late Paleocene (P5 zone) and continues to the top of the studied sequence. This change in facies has been used to map the contact between the Fort Union Formation of Paleocene age in this area, and the Wasatch Formation which was though to be of Eocene age. This study demonstrates that, as currently mapped, the lower part of the Wasatch Formation is Paleocene in age. Stratigraphically higher parts of the Wasatch, which presumably contain rocks of latest Paleocene (P6 zone) and earliest Eocene age, were not studied. -Authors

  8. Identification of a late Quaternary alluvial-aeolian sedimentary sequence in the Sichuan Basin, China

    NASA Astrophysics Data System (ADS)

    Feng, Jin-Liang; Ju, Jian-Ting; Chen, Feng; Hu, Zhao-Guo; Zhao, Xiang; Gao, Shao-Peng

    2016-03-01

    The late Quaternary sedimentary sequence in the northwestern part of the Sichuan Basin consists of five lithological units and with increasing depth include the: Chengdu Clay; Brown Clay; Red Clay; Sandy Silt; and basal Muddy Gravel. The genesis, provenance and age of the sediments, as well as the possible presence of hiatuses within this sequence are debated. Measurements of grain-size, magnetic susceptibility, quartz content, quartz δ18O values, element composition, and Sr-Nd isotopic concentrations of samples from a typical sedimentary sequence in the area provides new insights into the genesis and history of the sequence. The new data confirm that the sediments in study site are alluvial-aeolian in origin, with basal alluvial deposits overlain by aeolian deposits. Like the uppermost Chengdu Clay, the underlying Brown Clay and Red Clay are aeolian in origin. In contrast, the Silty Sand, like the basal Muddy Gravel, is an alluvial deposit and not an aeolian deposit as previously thought. Moreover, the succession of the aeolian deposits very likely contains two significant sedimentary hiatuses. Sedimentological analysis demonstrates that the source materials for the aeolian deposits in the northwestern part of the Sichuan Basin and those on the eastern Tibetan Plateau are different. Furthermore, the loess deposits on the eastern Tibetan Plateau are derived from heterogeneous local sources.

  9. Deposition, Diagenetic, or Bacterial Origin of Magnetite in Sediment Drifts From the Western Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Dulgar, S. E.; Brachfeld, S.; Ishman, S.; Ferré, E. C.

    2007-05-01

    A 607 meter sediment core from the western Antarctic Peninsula was collected during Ocean Drilling Program (ODP) Leg 178 at Site 1096. An abrupt shift, first recognized during the construction of the geomagnetic reversal stratigraphy, is observed in the magnetic mineral assemblage in core 1096A at 18 meters below seafloor (mbsf). This magnetic shift led us to question the fidelity of the geomagnetic reversal record. We evaluated the magnetic mineral assemblage using rock magnetic and electron microscopy techniques. Magnetic susceptibility showed variable concentration of magnetic material with depth, but not an abrupt change in concentration at 18 mbsf. Hysteresis data reveal a grain size shift at 18 mbsf. Magnetic particle size measurements show that with increasing depth the magnetic grain size increases. One possible explanation for the grain size shift is the presence of bacterial magnetite above 18 mbsf. However, TEM analysis did not conclusively prove the presence of magnetosomes. TEM images show grains in the 20-60 nm size range, but these grains were not in chains and they do not have the typical morphologies associated with bacterial magnetite. It is possible that these ultra fine grains are authigenic. Dissolution of these ultra fine magnetic particles could cause the grain size shift, with the smaller grains dissolving below18 mbsf. Temperature dependent FORC analyses are in progress to further characterize the particle size distribution above and below 18 mbsf. Curie temperature analyses indicate that magnetite is present above and below 18 mbsf. A magnetic iron sulfide with a Curie temperature of 350° C is present above 18 mbsf. X-ray microanalysis results agree with Curie temperature analyses, and show the presence of both Ti-poor iron oxides and iron sulfides in the magnetic extract. The presence of magnetic iron sulfides above 18 mbsf suggests iron-sulfur diagenesis is occurring with pyrrhotite preserved above 18 mbsf, and non-magnetic pyrite

  10. A Study of Finding Safer Aquifer in the Arsenic Contaminated Holocene Deposit; South-Western Bangladesh

    NASA Astrophysics Data System (ADS)

    Rahman, M.; Mano, A.; Udo, K.; Ishibashi, Y.

    2009-12-01

    The depositional pattern, geochemistry and mineralogy of the Arsenic (As) contaminated sediments along with the chemistry of groundwaters extracted from the Holocene deposit of an As hotspot, Kalaroa, Southwestern Bangladesh have been investigated in this study. These were done to elucidate a unified view that could explain the accumulation and distribution of As on the sediment surface and its subsequent release into the groundwater. Such view of As distribution mainly helped to find out eventually the possible existence of any safer aquifer that could provide adequate potable water to that targeted community. Two key geochemical parameters, the reaction rate Kr and the partition coefficient, Kd were found to be very promising in explaining the As release mechanism. Showing the realistic natural biotite dissolution process, the in-situ Kr that was derived by applying inverse mass balance model (2.72 × 10-16 /sec), was found to be slower by only three orders of magnitude than that was determined with the laboratory study (3.19×10-13 /sec). A parametric predictor equation, that can calculate the partition coefficient Kd based on the aquifer sediment’s minerals such as Fe and Al contents along with pore-water pH was developed in this study. Another Kd model based on the diffuse double layer surface complexation theory has also been developed to compare the appropriateness of the parametric Kd model. These two models were compared with the in-situ based field Kd data and were found in a good agreement. Integrating those two essential geochemical parameters (Kd and Kr), a 1D-Finite Difference numerical model was applied to observe and evaluate the As pollution scenario for the studied Holocene aquifer. The simulation showed very promising results introducing the idea that the deeper aquifer’s groundwaters would be remained safe against being contaminated with high As in future, due to the presence of a number of encouraging factors. The most significant among

  11. Evaporite deposition in a shallow perennial lake, Qaidam basin, western China

    SciTech Connect

    Schubel, K.A.; Lowenstein, T.K. ); Spencer, R.J. ); Pengxi, Z. )

    1991-03-01

    Evaporites accumulate in ephemeral saline-pans, shallow perennial lakes or lagoons, and deep perennial systems. Continuous brine trench exposures of Holocene evaporites from the Qaidam basin provide criteria for the recognition of shallow perennial lake sediments. Based on Landsat photographs, lateral extent of beds (at least 7 km), and sequence thicknesses (maximum 2.5 m), the paleolake is interpreted to have been less than 2.5 m deep and at least 120 km{sup 2} in area. Sediments consist of laminated siliciclastic mud overlain by mud-halite couplets (mm- to cm-scale layers), which represent one vertical shallowing- and concentrating-upwards sequence. The basal laminite marks the onset of deposition in this shallow perennial paleolake. Syndepositional halite textures and fabrics in the overlying mud-halite couplets include cumulates, rafts, and chevrons, draped by mud laminae, and halite layers truncated by horizontal dissolution surfaces (increasing in frequency upwards). Paleolake brines, determined from fluid inclusion melting temperatures, are Na-Mg-Cl-rich and evolve from 0.84 m Mg{sup 2} to 1.52 m Mg{sup 2+} (near the surface). Combinations of the following criteria may be used for the recognition of shallow, nonstratified, perennial lake sediments: lateral continuity of layers; muds undisrupted by subaerial exposure; vertical bottom-growth of halite; halite layers conformably overlain by mud; halite layers truncated by nonuniformly spaced horizontal dissolution surfaces; erosional scours and channels filled with cross-laminated gypsum, halite, and siliciclastic sand and mud; and salinity fluctuations over small stratigraphic intervals within an overall concentrating-upwards sequence.

  12. Precious metal-bearing epithermal deposits in western Patagonia (NE Lago Fontana region), Argentina

    NASA Astrophysics Data System (ADS)

    Lanfranchini, Mabel Elena; Etcheverry, Ricardo Oscar; de Barrio, Raúl Ernesto; Recio Hernández, Clemente

    2013-04-01

    Precious metal-bearing quartz veins occur at the northeastern sector of the Lago Fontana region in southwestern Argentina, within the context of the Andean continental magmatic arc environment. The deposits and their associated alteration zones are spatially related to a Cretaceous calc-alkaline magmatism represented by silicic dikes and hypabyssal intrusions, and hosted by a Late Jurassic to Cretaceous volcano-sedimentary sequence. The veins and related veinlets crop out discontinuously, in general terms in a NW-SE belt. The primary vein mineral assemblage is composed mostly of pyrite ± galena ± chalcopyrite > hematite ± arsenopyrite in silica gangue minerals. Chemical analyses of grab samples from selected quartz veins show as much as 5.7 ppm Au and 224 ppm Ag, as well as elevated Pb, Cu, and Zn. Hydrothermal fluids caused an innermost silicification and adularia-sericite alteration assemblage, and an external propylitic halo. Sulfur isotope values measured for sulfides (δSS from -1.90 to +1.56‰), and oxygen and hydrogen isotopes measured on quartz crystals and extracted primary fluid inclusion waters (δOO = -2.85 to +5.40‰; δDO = -106.0 to -103.4‰) indicate that mineralization probably formed from magmatic fluids, which were mixed with meteoric waters. Also, fluid inclusion data from quartz veins point out that these fluids had low salinity (1.7-4.2 wt% NaCl equiv.), and temperatures of homogenization between 180 and 325 °C. Mineralogical, petrographic and geochemical features for mineralized surface exposures indicate a typical adularia-sericite, low sulfidation epithermal system in the Lago Fontana area that represents a promising target for further exploration programs.

  13. Lithostratigraphy and depositional environments of the Vaqueros Formation in Hondo field, Capitan field, and the western Santa Ynez Mountains, California

    SciTech Connect

    Rigsby, C.A. ); Miles, G.A. ); Schwartz, D.E. )

    1991-02-01

    The Santa Ynez Mountains and the adjacent offshore areas are situated on the northwest edge of the western Transverse Range province. Oligocene-lower Miocene strata in this province record complex interactions among local and regional eustatics and local and regional tectonics and shed light on the sedimentary and tectonic history of this poorly understood region. Correlation of lithofacies units in Oligocene-lower Miocene Vaqueros Formation outcrops the Santa Ynez Mountains with Vaqueros cores from the Hondo and Capital fields leads to the delineation of three major facies tracts within the offshore and coastal areas: fan-delta conglomerates, shoreline sandstones and conglomerates, and inner shelf sandstones. Vaqueros strata at both Hondo and Capital fields are part of the inner shelf sandstone facies tract. Outcrops of the inner shelf facies typically consist of amalgamated packets of locally burrowed, cross-bedded, gravelly sandstones. In outcrop, bioturbation is most common near the tops of the cross-bed sets. In Hondo field a thinner, more basinward portion of this facies is characterized by bioturbated medium- to coarse-grained sandstones. Both in outcrops and at Hondo the base of the Vaqueros is marked by a sharp grain-size change and by a change from interbedded fluvial/deltaic strata below (the Alegria/Sespe formations) to inner shelf strata above (the Vaqueros Formation). The inner shelf facies tract represented by these three localities, fines, thins, and becomes more pervasively bioturbated in the present-day offshore direction suggesting a similar shoreline polarity however, the Oligocene-early Miocene paleogeography is more complex. Facies tracts present in outcrop in the western Santa Ynez Mountains become thinner and coarser in the present-day westerly direction and record deposition on a topographically and geomorphically complex shoreline.

  14. Magnetostratigraphic age and monsoonal evolution recorded by the thickest Quaternary loess deposit of the Lanzhou region, western Chinese Loess Plateau

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Li, Jijun; Guo, Benhong; Ma, Zhenhua; Li, Xiaomiao; Ye, Xiyan; Yu, Hao; Liu, Jia; Yang, Cheng; Zhang, Shengda; Song, Chunhui; Hui, Zhengchuang; Peng, Tingjiang

    2016-05-01

    The loess-paleosol sequences of the Chinese Loess Plateau (CLP) are major paleoclimatic archives which document the evolution of the East Asian Monsoon (EAM) and changes in the Northern Hemisphere ice sheets during the Quaternary glacial-interglacial cycles. However, the mechanisms regulating the trend of EAM variations on a tectonic scale are unclear. The loess deposits of the western CLP, which have a close relationship with tectonics and climate, are much better-suited to exploring these mechanisms than those of the central CLP. However, studies of long-term EAM evolution from the western CLP have been hindered by the lack of long, accurately-dated sequences with high sediment accumulation rates. Here, we address this problem via high resolution magnetostratigraphic, magnetic susceptibility and grain-size analyses of a 416.2 m-long drill core located at Xijin Village, near Lanzhou. Paleomagnetic dating indicates that the basal age of the Xijin loess is ∼2.2 Ma. The χ and grain-size records reveal that the East Asian Summer Monsoon (EASM) and East Asian Winter Monsoon (EAWM) strengthened synchronously at ∼1.24 Ma. Subsequently, during interglacial periods, the EASM began to penetrate, and then dominate, in the Lanzhou region. This was followed by two stepwise uptrends, commencing at ∼0.87 and ∼0.62 Ma, which resulted in an increasingly moist interglacial climate in the region. We suggest that the uplift of the Tibetan Plateau was largely responsible for these three stepwise enhancements of the EASM. Overall, however, the long-term trend of strengthening in EAWM in the area may have been primarily caused by long-term global cooling from the Late Pliocene onwards.

  15. High energy environment offshore deposits in the western Gulf of Corinth, Greece

    NASA Astrophysics Data System (ADS)

    Beckers, Arnaud; Mortier, Clément; Beck, Christian; Hubert-Ferrari, Aurélia; Reyss, Jean-Louis; Tripsanas, Efthymios; Sakellariou, Dimitris; De Batist, Marc; De Rycker, Koen; Bascou, Pascale; Strivay, David

    2013-04-01

    indicates a high energy environment origin like storm or tsunami. In the Trizonia Sub-Basin, one core located in the center of the Basin shows three clear granulometric peaks at 11, 27 and 53 cm under the seafloor. The coarser fraction of the third one is characterized by numerous organic matter elements. Higher resolution granulometry measurements and other textural parameters (Anisotropy of Magnetic Susceptibility) are needed to understand which processes are responsible for the transport and the deposition of these coarser layers, and to discuss an earthquake-induced origin.

  16. U-Th-Pb ion microprobe analysis of monazite from the Paleoproterozoic Karrat rare earth element (REE) deposit, western Greenland

    NASA Astrophysics Data System (ADS)

    Mott, A.; Grove, M.; Bird, D. K.

    2012-12-01

    The Karrat rare earth element (REE) deposit is located at 72°N on the Niaqornakavsak peninsula of Qeqertarssuq Island on the western coast of Greenland. Metasomatic alteration of an amphibolite host rock by carbonatite derived fluids resulted in REE mineralization in the Karrat Isfjord area. REE in the mineralization are primarily found in bastnasite, allanite, and monazite. In-situ analysis of monazite was conducted on samples obtained from three sites of mineralization: (1) the primary deposit at Niaqornakavsak consisting of a single distinct ~30m thick unit; (2) at Umiamako Nuna 7 km to the east of Niaqornakavsak where the majority of REE mineralization occurs within the first 20m of the surface; and (3) a 6m thick REE-rich vein 100m below the surface at Umiamako Nuna. Formation ages for monazite at Niaqornakavsak, Umiamako Nuna (surface), and Umiamako Nuna (vein) have been calculated using 207Pb/206Pb, 206Pb/238U, and 208Pb/232Th isotope ratios. Multiple isotope ratios were examined to determine the ideal method of monazite analysis based on the inherent issues of low U content of monazite, difficulties measuring 204Pb, common Pb corrections, and peak interferences resulting from high concentrations of REE. 208Pb/232Th analysis resulted in the best precision and smallest spread of values. Energy filtering was applied to 208Pb/232Th analyses in an effort to reduce interferences at several peaks. Although all three isotope ratio analyses result in a Paleoproterozoic age similar to the timing of convergence of the North Atlantic craton, Rae craton, and Aasiat domain as well as the emplacement of the Prøven Igneous Complex in Greenland (1.95-1.80Ga), the values range between 1.7-1.9Ga depending on the isotope ratio.

  17. Multistage amphiboles from the Galinge iron skarn deposit in Qiman Tagh, western China: evidence of igneous rocks replacement

    NASA Astrophysics Data System (ADS)

    Yu, M.; Feng, C.-Y.; Zhu, Y.-F.; Mao, J.-W.; Zhao, Y.-M.; Li, D.-X.

    2016-08-01

    Amphiboles from the Galinge skarn deposit, the largest iron (Fe) polymetallic skarn deposit in the Qiman Tagh metallogenic belt (western China), were formed by multistage fluid-rock interactions. Mineral analysis of the various amphiboles suggest that they were formed by the replacement of mafic to intermediate igneous rocks. The two alteration phases have formed three generations of compositionally distinct amphiboles: Amp-I: Ferro-edenitic hornblende (FE); Amp-II: Deep bluish-green magnesian-hastingsite (MH); Amp-III: Light greenish-beige ferro-actinolite (FA). The Amp-I preserves the primary igneous amphibole composition, and was subsequently replaced by Amp-II. The amphibole Cl content markedly increases from the FE (0.176 - 0.582 wt.%) to the MH (0.894 - 3.161 wt.%), and abruptly drops in the FA (0.017 - 0.039 wt.%). The Cl-rich MH contains the lowest concentration of Si [5.64 - 6.28 atoms per formula unit (apfu)], and the highest (K + Na) values (0.72 - 1.06 apfu) in the amphibole A-site with a high K/(K + Na) of 0.491 to 0.429. Both Mg and Fe contents of the MH and FA vary widely, possibly due to the interactions of magma-derived hydrothermal fluids with the basaltic / andesitic host rocks. Formation of the Cl-rich MH may have been associated with the early high-temperature and high-saline hydrothermal fluids, meanwhile the Cl-poor FA may have formed from later low-temperature and low-saline hydrothermal fluids. The MH plays an important role for consuming Cl carried by hydrothermal fluids. The Cl-rich fluids may have mobilized some elements, such as Fe, Al, Mg, Ca and Ti from the host rocks. Considerable amounts of Ti, Al, Mg and Fe were incorporated into the sphene and Fe-Ti oxides that coexist with the MH.

  18. Comparison of Mercury Mass Loading in Streams to Wet and Dry Atmospheric Deposition in Watersheds of the Western US: Evidence for Non-Atmospheric Mercury Sources

    NASA Astrophysics Data System (ADS)

    Domagalski, J. L.; Majewski, M. S.; Alpers, C. N.; Eckley, C.

    2015-12-01

    Many streams in the western United States (US) are listed as impaired by mercury (Hg), and it is important to understand the magnitudes of the various sources in order to implement management strategies. Atmospheric deposition of Hg and can be a major source of aquatic contamination, along with mine wastes, and other sources. Prior studies in the eastern US have shown that streams deliver less than 50% of the atmospherically deposited Hg on an annual basis. In this study, we compared annual stream Hg loads for 20 watersheds in the western US to measured wet and modeled dry deposition. Land use varies from undisturbed to mixed (agricultural, urban, forested, mining). Data from the Mercury Deposition Network was used to estimate Hg input from precipitation. Dry deposition was not directly measured, but can be modeled using the Community Multi-scale Air Quality model. At an undeveloped watershed in the Rocky Mountains, the ratio of stream Hg load to atmospheric deposition was 0.2 during a year of average precipitation. In contrast, at the Carson River in Nevada, with known Hg contamination from historical silver mining with Hg amalgamation, stream export exceeded atmospheric deposition by a factor of 60, and at a small Sierran watershed with gold mining, the ratio was 70. Larger watersheds with mixed land uses, tend to have lower ratios of stream export relative to atmospheric deposition suggesting storage of Hg. The Sacramento River was the largest watershed for which Hg riverine loads were available with an average ratio of stream Hg export to atmospheric deposition of 0.10. Although Hg was used in upstream historical mining operations, the downstream river Hg load is partially mitigated by reservoirs, which trap sediment. This study represents the first compilation of riverine Hg loads in comparison to atmospheric deposition on a regional scale; the approach may be useful in assessing the relative importance of atmospheric and non-atmospheric Hg sources.

  19. Geologic and geochemical insights into the formation of the Taiyangshan porphyry copper–molybdenum deposit, Western Qinling Orogenic Belt, China

    USGS Publications Warehouse

    Kun-Feng Qiu; Taylor, Ryan D.; Yao-Hui Song; Hao-Cheng Yu; Kai-Rui Song; Nan Li

    2016-01-01

    Taiyangshan is a poorly studied copper–molybdenum deposit located in the Triassic Western Qinling collisional belt of northwest China. The intrusions exposed in the vicinity of the Taiyangshan deposit record episodic magmatism over 20–30 million years. Pre-mineralization quartz diorite porphyries, which host some of the deposit, were emplaced at 226.6 ± 6.2 Ma. Syn-collisional monzonite and quartz monzonite porphyries, which also host mineralization, were emplaced at 218.0 ± 6.1 Ma and 215.0 ± 5.8 Ma, respectively. Mineralization occurred during the transition from a syn-collisional to a post-collisional setting at ca. 208 Ma. A barren post-mineralization granite porphyry marked the end of post-collisional magmatism at 200.7 ± 5.1 Ma. The ore-bearing monzonite and quartz monzonite porphyries have a εHf(t) range from − 2.0 to + 12.5, which is much more variable than that of the slightly older quartz diorite porphyries, with TDM2 of 1.15–1.23 Ga corresponding to the positive εHf(t) values and TDM1 of 0.62–0.90 Ga corresponding to the negative εHf(t) values. Molybdenite in the Taiyangshan deposit with 27.70 to 38.43 ppm Re suggests metal sourced from a mantle–crust mixture or from mafic and ultramafic rocks in the lower crust. The δ34S values obtained for pyrite, chalcopyrite, and molybdenite from the deposit range from + 1.3‰ to + 4.0‰, + 0.2‰ to + 1.1‰, and + 5.3‰ to + 5.9‰, respectively, suggesting a magmatic source for the sulfur. Calculated δ18Ofluid values for magmatic K-feldspar from porphyries (+ 13.3‰), hydrothermal K-feldspar from stockwork veins related to potassic alteration (+ 11.6‰), and hydrothermal sericite from quartz–pyrite veins (+ 8.6 to + 10.6‰) indicate the Taiyangshan deposit formed dominantly from magmatic water. Hydrogen isotope values for hydrothermal sericite ranging from − 85 to − 50‰ may indicate that magma degassing progressively depleted residual liquid in

  20. The origin of manganese-rich metasediments and their relationship to iron formation and base metal deposits, western Georgia piedmont

    SciTech Connect

    Wonder, J.D.

    1987-08-01

    Manganiferous metasediments (coticules), banded iron-formation, and tourmaline-quartz rocks (tourmalinites) are found in close spatial association to each other and to volcanogenic base metal sulfide and gold deposits in the Northern Piedmont of western Georgia. Coticules, which consist of up to 90% garnet and contain from 1 to 15 weight % MnO and 14 to 37 % Fe/sub 2/O/sub 3/, are often hosted by metabasalt. Tourmalinites occur as poorly-bedded aggregates or disseminations and are also found locally associated with metabasalt. Trace element analyses of coticules yield conflicting results. Cu + Co + Ni values and Zr/Cr ratios are low and indicate a hydrothermal origin. Alumina concentrations, Y/P/sub 2/O/sub 5/% ratios, and Th values indicate the probable presence of pelagic sediments in the protolith. Rare earth element patterns are enriched in the light elements and have slight negative Eu anomalies, resembling the patterns of pelagic clays most closely. The protolith of coticules was apparently a hydrothermal sediment with pelagic and/or terrigenous input. Tourmaline in tourmalinites is chemically similar to stratabound sulfide-related examples. Both coticules and tourmalinites are interpreted as metamorphosed seafloor exhalative sediments and thus indicate the potential for the presence of genetically related ore mineralization.

  1. Water on early Mars: Possible subaqueous sedimentary deposits covering ancient cratered terrain in western Arabia and Sinus Meridiani

    NASA Astrophysics Data System (ADS)

    Edgett, Kenneth S.; Parker, Timothy J.

    1997-11-01

    Western Arabia and northern Sinus Meridiani (30 deg N-10 deg S; 40 deg W-40 deg E) are almost entirely covered by wind-eroded, horizontally-bedded, sedimentary layers that lap against local topographic features. This portion of Mars' ancient cratered terrain is relatively low (less than 1 km elevation) and flat (sloping westward 0.7 m/km over 3,000 km). The region lacks valley network channels. We propose that at some time in early Martian history, this region was under water. The water hypothesis is strengthened by the presence of (1) a shore-like contact between smooth-surfaced deposits and ancient cratered terrain in central Sinus Meridiani, (2) polygonal structures in northern Sinus Meridiani, and (3) sand (which cannot be from airfall), possibly reworked by wind from the underlying sedimentary units. The September 1997 arrival of Mars Global Surveyor's thermal emission spectrometer offers an opportunity to begin to test this hypothesis by searching for carbonate and evaporite minerals among the sediment covering the region.

  2. A modified genetic model for the Huangshandong magmatic sulfide deposit in the Central Asian Orogenic Belt, Xinjiang, western China

    NASA Astrophysics Data System (ADS)

    Mao, Ya-Jing; Qin, Ke-Zhang; Li, Chusi; Tang, Dong-Mei

    2015-01-01

    The Huangshandong Ni-Cu deposit is the largest magmatic sulfide deposit discovered to date in the Central Asian Orogenic Belt in northern Xinjiang, western China. The host intrusion is a 274-Ma composite mafic-ultramafic intrusion consisting of four separate intrusive units: a large layered gabbroic sequence (phase I), a sheet-like ultramafic body (phase II), a dyke-like gabbronorite body (phase III), and an irregular ultramafic unit (phase IV). Important sulfide mineralization is present in the last three intrusive units, predominantly as disseminated and net-textured sulfides (pyrrhotite, pentlandite, and chalcopyrite). The Huangshandong mafic-ultramafic intrusive rocks are characterized by arc-like geochemical signatures such as low Ca content in olivine and negative Nb-Ta anomalies in whole rocks. This, together with a post-subduction setting for the East Tianshan in the Permian, suggests that the source mantle was modified previously by slab-derived fluids in the Carboniferous. The mantle-derived magma was ponded in a staging chamber in the lower part of the newly formed arc crust. The first batch of magma to arrive at Huangshandong was most fractionated and depleted in Ni, crystallizing Fe-rich and Ni-depleted olivine (Fo67, <300 ppm Ni). The second batch of magma was more primitive, crystallizing more primitive olivine (Fo81-84). The third batch of magma was also highly fractionated and depleted in Ni, crystallizing Fe-rich and Ni-depleted olivine (Fo72, ~600 ppm Ni). The final batch of magma became more primitive again, crystallizing the most primitive olivine (Fo81-86). The occurrence of rounded sulfide inclusions in olivine primocrysts in the Huangshandong ultramafic rocks indicates that immiscible sulfide liquid droplets were present during olivine crystallization. The Ni tenors of disseminated sulfide ores in the gabbronorite dyke vary mainly between 5 and 8 wt%, which are too high to have been produced by the parental magma of the dyke. The Ni, Cu, and

  3. Epithermal gold-siver deposits in the western United States: time-space products of evolving plutonic, volcanic and tectonic environments

    USGS Publications Warehouse

    Berger, B.R.; Bonham, H.F., Jr.

    1990-01-01

    The western United States has been the locus of considerable subaerial volcanic and plutonic igneous activity since the mid-Mesozoic. After the destruction of the Jurassic-Cretaceous magmatic arc-trench system, subduction was re-established in the Late Mesozoic with low-angle underthrusting of the oceanic plate beneath western North America. This resulted in crustal shortening during the Late Cretaceous to Early Tertiary and removal of the mantle lithosphere west of the Rocky Mountains. Commencing in the Eocene, flat subduction ceased, the volcanic arc began to re-establish itself along the continental margin, and the hingeline along the steepening subducting plate migrated from east to west. The crust east of the migrating hingeline was exposed to hot asthenosphere, and widespread tectonics and volcanic activity resulted. Hydrothermal activity accompanied the volcanism resulting in numerous epithermal gold-silver deposits. The temporal and spatial distributions of epithermal deposits in the region are therefore systematic and can be subdivided into discrete time intervals which are related to widespread changes in magmatic activity. Time intervals selected for discussion are Pre-Cenozoic, 66-55 Ma, 54-43 Ma, 42-34 Ma, 33-24 Ma, 23-17 Ma, and <17 Ma. Many of these intervals contain both sedimentary-rock and two varieties of volcanic-rock hosted deposits (adularia-sericite and alunite-kaolinite ?? pyrophyllite). Continental rifting is important to the formation of deposits, and, within any given region, it is at the initiation of deep rifting that alunite-kaolinite ?? pyrophyllite type epithermal deposits are formed. Adularia-sericite type deposits are most common, being related to all compositions and styles of volcanic activity. Therefore, the volcano-tectonic context of the western United States provides a unified framework in which to understand and explore for epithermal type deposits. ?? 1990.

  4. Late Quaternary sediment deposition of core MA01 in the Mendeleev Ridge, the western Arctic Ocean: Preliminary results

    NASA Astrophysics Data System (ADS)

    Park, Kwang-Kyu; Kim, Sunghan; Khim, Boo-Keun; Xiao, Wenshen; Wang, Rujian

    2014-05-01

    Late Quaternary deep marine sediments in the Arctic Ocean are characterized by brown layers intercalated with yellowish to olive gray layers (Poore et al., 1999; Polyak et al., 2004). Previous studies reported that the brown and gray layers were deposited during interglacial (or interstadial) and glacial (or stadial) periods, respectively. A 5.5-m long gravity core MA01 was obtained from the Mendeleev Ridge in the western Arctic Ocean by R/V Xue Long during scientific cruise CHINARE-V. Age (~450 ka) of core MA01 was tentatively estimated by correlation of brown layers with an adjacent core HLY0503-8JPC (Adler et al., 2009). A total of 22 brown layers characterized by low L* and b*, high Mn concentration, and abundant foraminifera were identified. Corresponding gray layers are characterized by high L* and b*, low Mn concentration, and few foraminiferal tests. Foraminifera abundance peaks are not well correlated to CaCO3 peaks which occurred with the coarse-grained (>0.063 mm) fractions (i.e., IRD) both in brown and gray layers. IRDs are transported presumably by sea ice for the deposition of brown layers and by iceberg for the deposition of gray layers (Polyak et al., 2004). A strong correlation coefficient (r2=0.89) between TOC content and C/N ratio indicates that the major source of organic matter is terrestrial. The good correlations of CaCO3 content to TOC (r2=0.56) and C/N ratio (r2=0.69) imply that IRDs contain detrital CaCO3 which mainly originated from the Canadian Arctic Archipelago. In addition, high kaolinite/chlorite (K/C) ratios mostly correspond to CaCO3 peaks, which suggests that the fine-grained particles in the Mendeleev Ridge are transported from the north coast Alaska and Canada where Mesozoic and Cenozoic strata are widely distributed. Thus, the Beaufort Gyre, the predominant surface current in the western Arctic Ocean, played an important role in the sediment delivery to the Mendeleev Ridge. It is worthy of note that the TOC and CaCO3 peaks are

  5. Stress changes from the 2008 Wenchuan earthquake and increased hazard in the Sichuan basin

    USGS Publications Warehouse

    Parsons, T.; Ji, C.; Kirby, E.

    2008-01-01

    On 12 May 2008, the devastating magnitude 7.9 (Wenchuan) earthquake struck the eastern edge of the Tibetan plateau, collapsing buildings and killing thousands in major cities aligned along the western Sichuan basin in China. After such a large-magnitude earthquake, rearrangement of stresses in the crust commonly leads to subsequent damaging earthquakes. The mainshock of the 12 May earthquake ruptured with as much as 9 m of slip along the boundary between the Longmen Shan and Sichuan basin, and demonstrated the complex strike-slip and thrust motion that characterizes the region. The Sichuan basin and surroundings are also crossed by other active strike-slip and thrust faults. Here we present calculations of the coseismic stress changes that resulted from the 12 May event using models of those faults, and show that many indicate significant stress increases. Rapid mapping of such stress changes can help to locate fault sections with relatively higher odds of producing large aftershocks. ??2008 Macmillan Publishers Limited. All rights reserved.

  6. Three dimensional surface slip partitioning of the Sichuan earthquake from Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    de Michele, M.; Raucoules, D.; de Sigoyer, J.; Pubellier, M.; Lasserre, C.; Pathier, E.; Klinger, Y.; van der Woerd, J.

    2009-12-01

    The Sichuan earthquake, Mw 7.9, struck the Longmen Shan range front, in the western Sichuan province, China, on 12 May 2008. It severely affected an area where little historical seismicity and little or no significant active shortening were reported before the earthquake (e.g. Gu et al., 1989; Chen et al., 1994; Gan et al., 2007). The Longmen Shan thrust system bounds the eastern margin of the Tibetan plateau and is considered as a transpressive zone since Triassic time that was reactivated during the India-Asia collision (e.g., Tapponnier and Molnar, 1977, Chen and Wilson 1996; Arne et al., 1997, Godard et al., 2009). However, contrasting geological evidences of sparse thrusting and marked dextral strike-slip faulting during the Quaternary along with high topography (Burchfiel et al., 1995; Densmore et al., 2007) have led to models of dynamically driven and sustained topography (Royden et al., 1997) limiting the role of earthquakes in relief building and leaving the mechanism of long term strain distribution in this area as an open question. Here we combine C and L band Synthetic Aperture Radar (SAR) offsets data from ascending and descending paths to retrieve the three dimensional surface slips distribution all along the earthquake ruptures of the Sichuan earthquake. We show a quantitative assessment of the amount of co-seismic slip and its partitioning at the surface.

  7. Three-dimensional seismic velocity structure in the Sichuan basin, China

    NASA Astrophysics Data System (ADS)

    Wang, Maomao; Hubbard, Judith; Plesch, Andreas; Shaw, John H.; Wang, Lining

    2016-02-01

    We present a new three-dimensional velocity model of the crust in the eastern margin of the Tibetan Plateau. The model describes the velocity structure of the Sichuan basin and surrounding thrust belts. The model consists of 3-D surfaces representing major geologic unit contacts and faults and is parameterized with Vp velocity-depth functions calibrated using sonic logs. The model incorporates data from 1166 oil wells, industry isopach maps, geological maps, and a digital elevation model. The geological surfaces were modeled based on structure contour maps for various units from oil wells and seismic reflection profiles. These surfaces include base Quaternary, Mesozoic, Paleozoic, and Proterozoic horizons. The horizons locally exhibit major offsets that are compatible with the locations and displacements of important faults systems. This layered, upper crustal 3-D model extends down to 10-15 km depth and illustrates lateral and vertical variations of velocity that reflect the complex evolution of tectonics and sedimentation in the basin. The model also incorporates 3-D descriptions of Vs and density for sediments that are obtained from empirical relationships with Vp using direct measurements of these properties in borehole logs. To illustrate the impact of our basin model on earthquake hazards assessment, we use it to calculate ground motions and compare these with observations for the 2013 Lushan earthquake. The result demonstrates the effects of basin amplification in the western Sichuan basin. The Sichuan CVM model is intended to facilitate fault systems analysis, strong ground motion prediction, and earthquake hazards assessment for the densely populated Sichuan region.

  8. Mid-Proterozoic detrital zircons and the depositional history of the Jack Hills (Narryer Gneiss Complex, Western Australia)

    NASA Astrophysics Data System (ADS)

    Bell, E. A.; Harrison, T. M.; Mojzsis, S. J.

    2012-12-01

    Quartz-biotite schists ("metaconglomerates" s.l.) in the Jack Hills outcrops of the Narryer Terrane of Western Australia host detrital >4 Ga zircons. These rocks are presumed to have been deposited at about 3 Ga and subsequently experienced metamorphism and granite intrusion at 2.45-2.6 Ga. Protoliths of the oldest detrital zircon population (>3.8 Ga) have not yet been identified, and the post-2.6 Ga history of the Jack Hills remains murky. Rare metavolcanic units are documented at ca. 1.8-1.9 Ga. Some metasediments near the Hadean zircon "discovery" site that are apparently young enough to have incorporated mid-Proterozoic detrital zircons are evidence of further geologic activity, although it is possible that these rocks were tectonically juxtaposed later. To further resolve the Proterozoic history of the Jack Hills, we report U-Pb age data for 60 detrital zircons extracted from two quartzites from the eastern Jack Hills (~50 km distant from the "discovery" site of Hadean zircons); in this sample suite 26 concordant zircons range in age from 0.168-3.49 Ga, with an age peak at ca. 2.6 Ga and a scattering of ages from 1.06-2.0 Ga. Zircon sources <1.8 Ga have not so far been identified in the Narryer Terrane and may point to far-field sediment transport. Several ca. 1.07 Ga zircons may derive from the Warakurna Large Igneous Province of the same age, which extends through much of central and Western Australia. One concordant zircon with a 206Pb/238U age of 0.166±6 Ga displays a patchy internal texture indicative of alteration; all other concordant grains are >1.06 Ga. Only 2 concordant zircons display ages >3 Ga, unlike the dominant mid-Archean signature from other reported Proterozoic sediments in the Jack Hills. All told, these quartzites display a significantly different provenance than other previously studied units from the terrane, with decreased importance of mid-Archean zircon sources and significantly younger (<1.06 Ga) ages of sedimentation than

  9. Genesis of superimposed hypogene and supergene Fe orebodies in BIF at the Madoonga deposit, Yilgarn Craton, Western Australia

    NASA Astrophysics Data System (ADS)

    Duuring, Paul; Hagemann, Steffen

    2013-03-01

    The Madoonga iron ore body hosted by banded iron formation (BIF) in the Weld Range greenstone belt of Western Australia is a blend of four genetically and compositionally distinct types of high-grade (>55 wt% Fe) iron ore that includes: (1) hypogene magnetite-talc veins, (2) hypogene specular hematite-quartz veins, (3) supergene goethite-hematite, and (4) supergene-modified, goethite-hematite-rich detrital ores. The spatial coincidence of these different ore types is a major factor controlling the overall size of the Madoonga ore body, but results in a compositionally heterogeneous ore deposit. Hypogene magnetite-talc veins that are up to 3 m thick and 50 m long formed within mylonite and shear zones located along the limbs of isoclinal, recumbent F1 folds. Relative to least-altered BIF, the magnetite-talc veins are enriched in Fe2O3(total), P2O5, MgO, Sc, Ga, Al2O3, Cl, and Zr; and depleted in SiO2 and MnO2. Mafic igneous countryrocks located within 10 m of the northern contact of the mineralised BIF display the replacement of primary igneous amphibole and plagioclase, and metamorphic chlorite by hypogene ferroan chlorite, talc, and magnetite. Later-forming, hypogene specular hematite-quartz veins and their associated alteration halos partly replace magnetite-talc veins in BIF and formed during, to shortly after, the F2-folding and tilting of the Weld Range tectono-stratigraphy. Supergene goethite-hematite ore zones that are up to 150 m wide, 400 m long, and extend to depths of 300 m replace least-altered BIF and existing hypogene alteration zones. The supergene ore zones formed as a result of the circulation of surface oxidised fluids through late NNW- to NNE-trending, subvertical brittle faults. Flat-lying, supergene goethite-hematite-altered, detrital sediments are concentrated in a paleo-topographic depression along the southern side of the main ENE-trending ridge at Madoonga. Iron ore deposits of the Weld Range greenstone belt record remarkably similar

  10. Porphyry Cu-Au and associated polymetallic Fe-Cu-Au deposits in the Beiya Area, western Yunnan Province, south China

    USGS Publications Warehouse

    Xu, X.-W.; Cai, X.-P.; Xiao, Q.-B.; Peters, S.G.

    2007-01-01

    The Alkaline porphyries in the Beiya area are located east of the Jinshajiang suture, as part of a Cenozoic alkali-rich porphyry belt in western Yunnan. The main rock types include quartz-albite porphyry, quartz-K-feldspar porphyry and biotite-K-feldspar porphyry. These porphyries are characterised by high alkalinity [(K2O + Na2O)% > 10%], high silica (SiO2% > 65%), high Sr (> 400??ppm) and 87Sr/86Sr (> 0.706)] ratio and were intruded at 65.5??Ma, between 25.5 to 32.5??Ma, and about 3.8??Ma, respectively. There are five main types of mineral deposits in the Beiya area: (1) porphyry Cu-Au deposits, (2) magmatic Fe-Au deposits, (3) sedimentary polymetallic deposits, (4) polymetallic skarn deposits, and (5) palaeoplacers associated with karsts. The porphyry Cu-Au and polymetallic skarn deposits are associated with quartz-albite porphyry bodies. The Fe-Au and polymetallic sedimentary deposits are part of an ore-forming system that produced considerable Au in the Beiya area, and are characterised by low concentrations of La, Ti, and Co, and high concentrations of Y, Yb, and Sc. The Cenozoic porphyries in western Yunnan display increased alkalinity away from the Triassic Jinshajiang suture. Distribution of both the porphyries and sedimentary deposits in the Beiya area are interpreted to be related to partial melting in a disjointed region between upper mantle lithosphere of the Yangtze Plate and Gondwana continent, and lie within a shear zone between buried Palaeo-Tethyan oceanic lithosphere and upper mantle lithosphere, caused by the subduction and collision of India and Asia. ?? 2006 Elsevier B.V. All rights reserved.

  11. Pliocene-Quaternary contourite depositional system along the south-western Adriatic margin: changes in sedimentary stacking pattern and associated bottom currents

    NASA Astrophysics Data System (ADS)

    Pellegrini, Claudio; Maselli, Vittorio; Trincardi, Fabio

    2016-02-01

    The Pliocene-Quaternary history of the south-western Adriatic margin, represented by a complex contourite depositional system, records the palaeoceanography of the basin and the interactions between oceanographic processes and the uneven slope morphology that resulted from tectonic deformation. Three main stages can be recognized: (1) during the Pliocene, a giant sediment drift formed on the southern flank of the slope-transverse Gondola anticline that focused and accelerated the flow of slope-parallel bottom currents; (2) since the early to middle Pleistocene transition, a reorganization of bottom-current pathways led to a sharp change in the sedimentary architecture of the margin that became dominated by the growth of contourite deposits; (3) as of 350 ka, landward-migrating contourites on the outer shelf (less than 120 m water depth) reflect the presence of bottom currents also in shallow waters. This analysis of the sedimentary stacking pattern of the contourite depositional system that developed along the south-western Adriatic margin since the Pliocene enables disentangling the processes that controlled changes in bottom-current activity, demonstrating that bottom-current deposits constitute the bulk of depositional sequences at the Milankovitch timescale.

  12. Mineralogical study of sediment-hosted gold deposits in the Yangshan ore field, Western Qinling Orogen, Central China

    NASA Astrophysics Data System (ADS)

    Liang, Jinlong; Sun, Weidong; Zhu, Sanyuan; Li, He; Liu, Yulong; Zhai, Wei

    2014-05-01

    The Yangshan gold ore field is located in the southern subzone of the Western Qinling Orogen. Mineralization is confined by the east-west-striking Anchanghe thrust fault zone. These subparallel faults constitute a branch of the regional Mianlue structural zone, crosscutting Middle Devonian carbonaceous carbonate and clastic rock sequences, an ore-bearing unit locally named the Sanhekou Formation. The metasedimentary clastic and carbonate rocks containing fine-grained sulfides are the main host rocks of the deposit, with minor mineralization occurring as coarse-grained pyrite-quartz veinlets in black shale and as dissemination in some plagiogranite dykes. Electron microprobe (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses show that arsenian pyrite and arsenopyrite are the major hosts for gold with tens of ppm up to weight percent levels of Au, and the Au contents in arsenopyrite are one order of magnitude higher than those in pyrite. A negative correlation of As and S in arsenian pyrite is consistent with the substitution of As for S in the mineral. Both arsenian pyrite and arsenopyrite in the Yangshan ore field show chemical zonations with middle parts (mantle) enriched in As and Au relative to cores and the outermost rims, reflecting the chemical evolution of ore-forming fluids. High resolution transmission electron microscopy (HRTEM) analysis failed to identify any nanoparticle of native gold even in the highest Au parts of arsenopyrite. This observation combined with the relatively homogenous distribution of Au, a positive correlation of As and Au, and Au/As ratios below the solubility limit of gold in arsenian pyrite and arsenopyrite, suggests that invisible gold is likely present as structurally bound Au+1 in sulfides, although our work cannot exclude the existence of Au nanoparticles in arsenian pyrite as identified in American Carlin-type gold deposits. Submicron native gold may be much more easily found in

  13. [Spatial distribution and ecological significance of heavy metals in soils from Chatian mercury mining deposit, western Hunan province].

    PubMed

    Sun, Hong-Fei; Li, Yong-Hu; Ji, Yan-Fang; Yang, Lin-Sheng; Wang, Wu-Yi

    2009-04-15

    Ores, waste tailings and slag, together with three typical soil profiles (natural soil profiles far from mine entrance and near mine entrance, soil profile under slag) in Chatian mercury mining deposit (CMD), western Hunan province were sampled and their concentrations of mercury (Hg), arsenic (As), lead (Pb), cadmium (Cd), zinc (Zn) were determined by HG-ICP-AES and ICP-MS. Enrichment factor and correlation analysis were taken to investigate the origins, distribution and migration of Hg, as well as other heavy metals in the CMD. The results show that Hg is enriched in the bottom of the soil profile far from mine entrance but accumulated in the surface of soil profiles near mine entrance and under slag. The soil profiles near mine entrance and under slag are both contaminated by Hg, while the latter is contaminated more heavily. In the soil profile under slag, Hg concentration in the surface soil, Hg average concentration in the total profile, and the leaching depth of soil Hg are 640 microg x g(-1), (76.74 +/- 171.71) microg x g(-1), and more than 100 cm, respectively; while 6.5 microg x g(-1), (2.74 +/- 1.90) microg x g(-1), and 40 cm, respectively, are found in the soil profile near mine entrance. Soil in the mercury mine area is also polluted by Cd, As, Pb, Zn besides metallogenic element Hg, among which Cd pollution is relatively heavier than others. The mobility of the studied heavy metals in soil follows the order as Hg > Cd > As > Zn approximately equal to Pb. The leaching depth of the heavy metals is influenced by total concentration in the surface soil and soil physico-chemical parameters. The origins, distribution and migration of heavy metals in soil profile in the mining area are related to primary geological environment, and strongly influenced by human mining activities. PMID:19545023

  14. Franciscan olistoliths in Upper Cretaceous conglomerate deposits, Western Transverse Ranges, California: Implications for basin morphology and tectonic history

    SciTech Connect

    Reed, W.E.; Campbell, M.D. . Dept. of Earth and Space Sciences)

    1993-04-01

    Compositional analyses reveal that Upper Cretaceous sediments exposed in the Western Transverse Ranges of CA were deposited in submarine fan systems in a forearc basin. Point count data suggest a magmatic arc/recycled orogen as the dominant provenance for these sediments. Paleocurrent measurements from conglomerates in these sediments yield a northerly transport direction. Removal of ca. 90[degree] of clockwise rotation and 70 km of right-lateral slip restore this section to a position west of the San Diego area. The forearc basin would have had a N-S orientation, with the bulk of sediments supplied by the Peninsular Ranges to the east. Evidence of the erosion of the accretionary wedge is provided by the presence of large, internally stratified olistoliths of Franciscan material interbedded with and surrounded by upper Cretaceous conglomerate. Petrographic, quantitative SEM, and microprobe analyses indicate the presence of diagnostic Franciscan mineralogy, including glaucophane, riebeckite, lawsonite, and serpentine. Olistoclasts of chert, jadeitic graywacke, serpentine, and blueschist are found intermixed with the conglomerates in close association with the olistoliths. This association provides strong field evidence that recirculation of melange material within the subduction zone was active and well-established by late Cretaceous time. Inferences regarding the forearc system morphology can be drawn from these observations. The occurrence of coarse, easterly-derived conglomerates surrounded by large, stratified, but sheared, westerly-derived Franciscan debris, suggests a narrow, relatively steep-sided basin. Paleocurrent measurements gave no indication of axial transport within the basin. This morphology suggests that, in late Cretaceous time, the forearc basin was youthful, with a narrow arc-trench gap. Thus, relative convergence rates between the North American and Pacific plates were possibly slower than Tertiary convergence rates.

  15. Sedimentary Deposits from the 17 July 2006 Western Java Tsunami, Indonesia: Use of Grain Size Analyses to Assess Tsunami Flow Depth, Speed, and Traction Carpet Characteristics

    NASA Astrophysics Data System (ADS)

    Moore, Andrew; Goff, James; McAdoo, Brian G.; Fritz, Hermann M.; Gusman, Aditya; Kalligeris, Nikos; Kalsum, Kenia; Susanto, Arif; Suteja, Debora; Synolakis, Costas E.

    2011-11-01

    The 2006 western Java tsunami deposited a discontinuous sheet of sand up to 20 cm thick, flooded coastal southern Java to a depth of at least 8 m and inundated up to 1 km inland. In most places the primarily heavy mineral sand sheet is normally graded, and in some it contains complex internal stratigraphy. Structures within the sand sheet probably record the passage of up to two individual waves, a point noted in eyewitness accounts. We studied the 2006 tsunami deposits in detail along a flow parallel transect about 750 m long, 15 km east of Cilacap. The tsunami deposit first becomes discernable from the underlying sediment 70 m from the shoreline. From 75 to 300 m inland the deposit has been laid down in rice paddies, and maintains a thickness of 10-20 cm. Landward of 300 m the deposit thins dramatically, reaching 1 mm by 450 m inland. From 450 m to the edge of deposition (around 700 m inland) the deposit remains <1 mm thick. Deposition generally attended inundation—along the transect, the tsunami deposited sand to within about 40 m of the inundation limit. The thicker part of the deposit contains primarily sand indistinguishable from that found on the beach 3 weeks after the event, but after about 450 m (and roughly coinciding with the decrease in thickness) the tsunami sediment shifts to become more like the underlying paddy soil than the beach sand. Grain sizes within the deposit tend to fine upward and landward, although overall upward fining takes place in two discrete pulses, with an initial section of inverse grading followed by a section of normal grading. The two inversely graded sections are also density graded, with denser grains at the base, and less dense grains at the top. The two normally graded sections show no trends in density. The inversely graded sections show high density sediment to the base and become less dense upward and represents traction carpet flows at the base of the tsunami. These are suggestive of high shear rates in the flow

  16. Depositional evolution of the Early Cretaceous Sihetun Lake and implications for regional climatic and volcanic history in western Liaoning, NE China

    NASA Astrophysics Data System (ADS)

    Jiang, Baoyu; Fürsich, Franz T.; Hethke, Manja

    2012-06-01

    Numerous well-known fossils of the Jehol Biota, including early birds, feathered theropods, primitive mammals, and putative early angiosperms, have been discovered in lacustrine deposits (Lake Sihetun) of the Lower Cretaceous Yixian Formation of western Liaoning province, NE China. Based on extensive field investigations and four high-resolution excavations, we document in detail the spatio-temporal changes of sedimentary facies, facies associations and limnic community relicts, reconstruct the depositional history, and discuss the significance of these deposits regarding the regional climatic and volcanic history. Four phases are recognized in the history of Lake Sihetun. They are: (1) a phase of fluctuating but gradually rising water level indicated by subaerial and shallow-water lacustrine deposits, (2) a lake with beach-nearshore facies along the marginal areas and suspension-dominated lake floor facies in central areas, (3) a lake phase with a lake floor dominated by hyperpycnal flows, and (4) progradation of a fan delta. Two distinct depositional conditions are observed: stratified and unstratified lake intervals. The former occurred mainly during the second phase and produced clay-poor and clay-rich laminae, whereas the latter developed during the other three phases, and were dominated by deposition of subaqueous sedimentary density flows. These alternations of depositional conditions in offshore lacustrine deposits suggest that the Yixian Formation may have formed under a transitional climate regime fluctuating gradually from warm and dry to warm and humid conditions. Resurgent volcanism is inferred to have become stronger during the late phase of lake development based on distribution of deposits characterizing the unstratified lake interval and volcanic rocks of the overlying Upper Lava unit, a higher content of primary pyroclastic fragments, and evidence of strong syndepositional disturbance.

  17. Use of passive sampling methods and models to understand sources of mercury deposition to high elevation sites in the Western United States.

    PubMed

    Huang, Jiaoyan; Gustin, Mae Sexauer

    2015-01-01

    To understand gaseous oxidized mercury (GOM) sources to the Western US, data were collected with passive samplers for ambient GOM concentrations and dry deposition at 10 sites from the coast of the Pacific Ocean to Great Basin National Park. Tests were done to better understand the samplers and the materials used. Measured dry deposition of GOM was significantly higher at sites >2000 m elevation relative to those below due to high GOM concentrations and atmospheric turbulence. At these high elevation sites, GOM dry deposition was higher in spring due to long-range transport from Asia (air parcels from the free troposphere) and some high GOM dry deposition events were related to regional emissions. Dry deposition of GOM at two sites was calculated using the passive sampler data and a multiple-resistance model. A previously developed relationship between the sampling rate of the passive sampler and GOM concentrations was used to estimate dry deposition and a scaling factor of 3 was used to adjust GOM concentrations, due to underestimation by KCl-coated denuder measurements. With the scaling factor of 3, modeled deposition was in the range of results estimated from two different models settings. However, dry deposition did not correlate consistently with either model. The disagreement could be due to uncertainties associated with measurements and/or modeling, or different GOM compounds existing in the atmosphere. If the atmospheric GOM compounds are known, dry deposition velocities could be estimated more accurately. Lastly, we investigated the potential for use of a new sampling material for GOM and checked the efficiency of the passive sampler. PMID:25485926

  18. Helicopter EM (ZTEM-VTEM) survey results over the Nuqrah copper-lead-zinc-gold SEDEX massive sulphide deposit in the Western Arabian Shield, Kingdom of Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Legault, Jean M.; Izarra, Carlos; Prikhodko, Alexander; Zhao, Shengkai; Saadawi, Emad M.

    2015-10-01

    Magnetic and electromagnetic (EM) results from two helicopter EM surveys, a time-domain (VTEM) and AFMAG (ZTEM), are compared over the Nuqrah sedimentary exhalative (SEDEX) massive sulphide deposits in the Western Arabian Shield of the Kingdom of Saudi Arabia. The magnetic and EM data from both surveys map the major controlling structures that host the Nuqrah North and South deposits. Neither Nuqrah deposits stand out as distinctive aeromagnetic anomalies, but both EM surveys define the massive sulphide mineralised vent and bedded portions of the SEDEX orebodies. ZTEM is interpreted to be more capable in defining the larger, lower conductance and less mineralised distal portions of the SEDEX system. The modelled ZTEM also defines a down-dip extension of the Nuqrah South zone below a depth of 750 m.

  19. Substrate-independent feeding mode of the ichnogenus Phymatoderma from the Lower Jurassic shelf-sea deposits of central and western Europe

    NASA Astrophysics Data System (ADS)

    Izumi, Kentaro; Rodríguez-Tovar, Francisco J.; Piñuela, Laura; García-Ramos, José Carlos

    2014-10-01

    Deposit-feeding strategies recorded in the ichnogenus Phymatoderma from the Lower Jurassic shelf-sea deposits in central (Dotternhausen, southwest Germany) and western Europe (Asturias, north Spain) are revealed by geochemical and microscopic analyses. Thin-section observations showed that the trace-maker of Phymatoderma from Asturias ingested bioclastic skeletal sediments, and that from Dotternhausen ingested fine-grained siliciclastic sediments. Geochemical analysis elucidated that the trace-makers of Phymatoderma from both Asturias and Dotternhausen were non-selective deposit feeders (i.e., indiscriminately ingesting sediment particles on the seafloor), although the ingested sediments were significantly different in lithology. Microscopic analysis revealed that the Early Jurassic Phymatoderma-producers mainly fed on calcareous nannoplankton, i.e., coccolithophores, dinoflagellates, as well as their phytodetritus. Here, we demonstrate a substrate-independent feeding mode in the Early Jurassic Phymatoderma-producers, which accords with the similar morphologic, paleogeographic, and chronologic context of Phymatoderma from Asturias and Dotternhausen.

  20. Study on 3-D velocity structure of crust and upper mantle in Sichuan-yunnan region, China

    USGS Publications Warehouse

    Wang, C.; Mooney, W.D.; Wang, X.; Wu, J.; Lou, H.; Wang, F.

    2002-01-01

    Based on the first arrival P and S data of 4 625 regional earthquakes recorded at 174 stations dispersed in the Yunnan and Sichuan Provinces, the 3-D velocity structure of crust and upper mantle in the region is determined, incorporating with previous deep geophysical data. In the upper crust, a positive anomaly velocity zone exists in the Sichuan basin, whereas a negative anomaly velocity zone exists in the western Sichuan plateau. The boundary between the positive and negative anomaly zones is the Longmenshan fault zone. The images of lower crust and upper mantle in the Longmenshan fault, Xianshuihe fault, Honghe fault and others appear the characteristic of tectonic boundary, indicating that the faults litely penetrate the Moho discontinuity. The negative velocity anomalies at the depth of 50 km in the Tengchong volcanic area and the Panxi tectonic zone appear to be associated with the temperature and composition variations in the upper mantle. The overall features of the crustal and the upper mantle structures in the Sichuan-Yunnan region are the lower average velocity in both crust and uppermost mantle, the large crustal thickness variations, and the existence of high conductivity layer in the crust or/and upper mantle, and higher geothermal value. All these features are closely related to the collision between the Indian and the Asian plates. The crustal velocity in the Sichuan-Yunnan rhombic block generally shows normal.value or positive anomaly, while the negative anomaly exists in the area along the large strike-slip faults as the block boundary. It is conducive to the crustal block side-pressing out along the faults. In the major seismic zones, the seismicity is relative to the negative anomaly velocity. Most strong earthquakes occurred in the upper-mid crust with positive anomaly or normal velocity, where the negative anomaly zone generally exists below.

  1. Geochronology of the western and central Brooks Range, Alaska: Implications for the geologic evolution of the Anarraaq and Red Dog Zn-Pb-Ag deposits

    USGS Publications Warehouse

    Rombach, C.S.; Layer, P.W.

    2004-01-01

    A compilation of published geochronology of rocks and minerals from the western and central Brooks Range provides a framework for understanding the complex history of the Brooks Range and northern Alaska. A simplified timeline of events comprises (1) Devonian extension, (2) Mississippian extension and Zn-Pb-Ag mineralization, (3) a passive interval, (4) pre-Brooks Range orogeny rock-formation and thermal event, (5) inception of Brooks Range orogeny, (6) exhumation and the end of main-stage deformation, and (7) subsequent episodic deformation. This compilation is supplemented by new 40Ar/39Ar dates of white mica from the Anarraaq and Red Dog Zn-Pb-Ag (+ barite) deposits from the western Brooks Range. The deposits are hosted in black shale and carbonate rocks of the Late Mississippian-Early Pennsylvanian Kuna Formation. Quartz-pyrite-white mica grains in sedimentary rocks above the Anarraaq deposit yield an age of 195.0 ?? 2.0 Ma, and paragenetically late quartz-pyrite-white mica from the Main orebody at the Red Dog deposit has an age of 126.1 ?? 0.7 Ma. These white micas are much younger than the age of Zn-Pb-Ag mineralization at Red Dog (338 ?? 5.8 Ma Re-Os age of pyrite). The date for white mica from Anarraaq (???195 Ma) appears to be related to a large-scale thermal event in the region immediately before the inception of the Brooks Range orogeny. The white mica from the Red Dog deposit (???126 Ma) correlates with the later stages of the orogeny, a period of blueschist metamorphism, extension, and rapid exhumation, which varied with geographic location. These dates suggest that the Red Dog deposits underwent significant hydrothermal overprinting during multiple episodes of the Brooks Range orogeny. ?? 2004 by Economic Geology.

  2. Magmatic and related mineral deposits of the Pan-African Saldania belt in the Western Cape Province, South Africa

    NASA Astrophysics Data System (ADS)

    Rozendaal, A.; Scheepers, R.

    1995-07-01

    Mineral deposits and prospects of the Pan-African Saldania orogenic belt in the Western Cape Province, South Africa, are reviewed. The polyphase, deformed, low-grade metamorphosed, volcano-sedimentary Malmesbury Group constitutes a complex, poorly understood supracrustal sequence that has been loosely subdivided into the Tygerberg, Swartland and Boland tectono-stratigraphic terranes on the basis of NW-trending fault zones. Syn- and post-tectonic granitoids of the Cape Granite Suite selectively intruded these terranes. Early S-types preferred the Tygerberg terrane, whereas the later I-types dominate the remaining areas. Anorogenic A-type granites, however, occur in all three terranes. Despite the absence of operating base or precious metal mines in the area, this study has established at least four metal associations directly or indirectly related to the intrusions: i) Cassiterite-wolframite (±Au, Cu, Mo, Zn, As, Fe-sulphides) in quartz and quartz/aplite veins hosted by tour-malinized and locally greissenized S-type granite. Similar exo-granitic veins occur in proximal metamorphites; ii) Juxtaposed, disseminated, stockwork breccia and vein style CuMoFe(Au)-sulphide mineralization hosted by mafic- to intermediate-intrusions of high-K calc-alkaline, I-type affinity; iii) CuMoAu-sulphides hosted by hydraulic breccia pipes, stocks and veins occurring in anorogenic A-type alkali feldspar granites and amphibole quartz syenites; iv) Scheelite with minor CuMoAu-sulphides associated with endo- and exo-skams spatially related to I-type monzogranite, granite and alkali feldspar granite. The first three associations occur along the Yzerfontein-Helderberg-zone, a 180 km lineament in the Tygerberg terrane, exploited by syn-, late- and post-tectonic intrusions and their related mineralization. The fourth association is typical of the Boland terrane. The spatial and temporal relationships among the various metal associations are interpreted as the result of

  3. Abiogenic Fischer-Tropsch synthesis of methane at the Baogutu reduced porphyry copper deposit, western Junggar, NW-China

    NASA Astrophysics Data System (ADS)

    Cao, MingJian; Qin, KeZhang; Li, GuangMing; Evans, Noreen J.; Jin, LuYing

    2014-09-01

    Methane is widely developed in hydrothermal fluids from reduced porphyry copper deposits, but its origin remains enigmatic. The occurrence of methane in fluid inclusions at the Late Carboniferous Baogutu reduced porphyry copper deposit in western Junggar, Xinjiang, NW-China, presents an excellent opportunity to address this problem. A systematic study including fluid inclusion Laser-Raman and CO2-CH4 carbon isotope analyses, igneous and hydrothermal mineral H-O isotope analyses, and in situ major, trace element and Sr isotopic analyses of hydrothermal epidote was conducted to constrain the origin of CH4 and CH4-rich fluids. The δ2H and δ18O of water in equilibrium with igneous biotite ranges from -65.0‰ to -66.0‰ and +7.2‰ to +7.4‰, respectively, indicating notable degassing of probably supercritical fluids in the magma chamber. The wide range of δ2H (-58.0‰ to -107.0‰, n = 23) for water within quartz suggests the existence of significant hydrothermal fluid boiling. Water-rock interaction is the most likely mechanism leading to the wide range of δ18O values for water in vein quartz with water/rock ratios (wt.% in O) of 0.15 to 0.75 and 0.13 to 0.46 for a closed and open system, respectively. Detailed Laser-Raman analyses indicate CO2 in apatite included in granodiorite porphyry phenocrystic biotite that records the carbon species of the early stage magmatic stage, whereas later hydrothermal fluids containing CH4 with trace or without CO2 are found in inclusions of vein quartz. We propose that CH4 is probably transformed from CO2 by Fischer-Tropsch type reactions at 500 °C, assumed from CO2-CH4 C isotope equilibrium. The (87Sr/86Sr)i of hydrothermal epidote yields values of 0.70369-0.70404, consistent with that reported for the whole rocks. The δ13CCH4 (-28.6‰ to -22.6‰) and δ2HCH4 (-108.0‰ to -59.5‰) are characteristic of abiogenic methane. The measured δ13CCO2 shows a slightly depleted 13C (-13.5‰ to -7.2‰) relative to upper mantle

  4. Structural controls on gold mineralization on the margin of the Yilgarn craton, Albany-Fraser orogen: The Tropicana deposit, Western Australia

    NASA Astrophysics Data System (ADS)

    Blenkinsop, Tom G.; Doyle, Mark G.

    2014-10-01

    The Tropicana gold deposit is located adjacent to the margin of the Yilgarn craton in the Albany-Fraser orogen, Western Australia. The deposit is hosted in granulite facies quartzo-feldspathic gneisses of the Archean Tropicana Gneiss. Ore bodies comprise biotite-pyrite alteration concentrated in shear zones that formed during NE-SW shortening in the late Archean, and clearly postdate the formation and deformation of high-grade gneiss fabrics (D1 and D2). The orientation of the ore bodies is controlled by the shear zones that are in turn localised by the gneissic banding. Mineralization also involved solution and coeval microfracturing and veining of more competent pegmatitic units. The mineralizing event (D3) was followed by at least two further deformations, which reactivated and overprinted the biotite fabrics with sericite and chlorite, created new shear zones, and affected gold distribution. D5 consisted of dextral shear on ∼E-W shear zones, which subdivide the deposit into five major structural domains. The importance of structurally controlled permeability at Tropicana is similar in cratonic lode gold deposits, as is the protracted deformation/fluid flow history. Like Renco mine in Zimbabwe, Tropicana gold deposit was formed by hydrothermal fluid flow peripheral to the craton: economic gold mineralization was clearly post-peak metamorphism.

  5. Deposition of sedimentary organic matter in black shale facies indicated by the geochemistry and petrography of high-resolution samples, blake nose, western North Atlantic

    USGS Publications Warehouse

    Barker, C.E.; Pawlewicz, M.; Cobabe, E.A.

    2001-01-01

    A transect of three holes drilled across the Blake Nose, western North Atlantic Ocean, retrieved cores of black shale facies related to the Albian Oceanic Anoxic Events (OAE) lb and ld. Sedimentary organic matter (SOM) recovered from Ocean Drilling Program Hole 1049A from the eastern end of the transect showed that before black shale facies deposition organic matter preservation was a Type III-IV SOM. Petrography reveals that this SOM is composed mostly of degraded algal debris, amorphous SOM and a minor component of Type III-IV terrestrial SOM, mostly detroinertinite. When black shale facies deposition commenced, the geochemical character of the SOM changed from a relatively oxygen-rich Type III-IV to relatively hydrogen-rich Type II. Petrography, biomarker and organic carbon isotopic data indicate marine and terrestrial SOM sources that do not appear to change during the transition from light-grey calcareous ooze to the black shale facies. Black shale subfacies layers alternate from laminated to homogeneous. Some of the laminated and the poorly laminated to homogeneous layers are organic carbon and hydrogen rich as well, suggesting that at least two SOM depositional processes are influencing the black shale facies. The laminated beds reflect deposition in a low sedimentation rate (6m Ma-1) environment with SOM derived mostly from gravity settling from the overlying water into sometimes dysoxic bottom water. The source of this high hydrogen content SOM is problematic because before black shale deposition, the marine SOM supplied to the site is geochemically a Type III-IV. A clue to the source of the H-rich SOM may be the interlayering of relatively homogeneous ooze layers that have a widely variable SOM content and quality. These relatively thick, sometimes subtly graded, sediment layers are thought to be deposited from a Type II SOM-enriched sediment suspension generated by turbidities or direct turbidite deposition.

  6. Oxidized and reduced mineral assemblages in greenstone belt rocks of the St. Ives gold camp, Western Australia: vectors to high-grade ore bodies in Archaean gold deposits?

    NASA Astrophysics Data System (ADS)

    Neumayr, Peter; Walshe, John; Hagemann, Steffen; Petersen, Klaus; Roache, Anthony; Frikken, Peter; Horn, Leo; Halley, Scott

    2008-03-01

    Hydrothermal sulfide-oxide-gold mineral assemblages in gold deposits in the Archaean St. Ives gold camp in Western Australia indicate extremely variable redox conditions during hydrothermal alteration and gold mineralization in space and time. Reduced alteration assemblages (pyrrhotite-pyrite) occur in deposits in the southwest of the camp (e.g., Argo, Junction deposits) and moderately to strongly oxidized assemblages (magnetite-pyrite, hematite-pyrite) occur in deposits in the Central Corridor in the northeast (e.g., North Orchin, Revenge deposits). Reduced mineral assemblages flank the Central Corridor of oxidized deposits and, locally, cut across it along E-W trending faults. Oxidized mineral assemblages in the Central Corridor are focused on gravity lows which are interpreted to reflect abundant felsic porphyritic intrusions at about 1,000 m below present surface. Hydrothermal magnetite predates and is synchronous with early phases of gold-associated albite-carbonate-pyrite-biotite-chlorite hydrothermal alteration. Later-stage, gold-associated pyrite is in equilibrium with hematite. The spatial distribution and temporal sequence of iron sulfides and oxides with gold indicate the presence of at least two spatially restricted but broadly synchronous hydrothermal fluids with contrasting redox states. Sulfur isotope constraints support the argument that the different mineral assemblages reflect differences in redox conditions. The δ 34S values for pyrite for the St. Ives gold camp range between -8.4‰ and +5.1‰ with the negative values occurring in oxidized magnetite-rich domains and slightly negative or positive values occurring in reduced, pyrrhotitic domains. Preliminary spatial and paragenetic analysis of the distribution of iron sulfides and oxides in the St. Ives camp suggests that gold grades are highest where the redox state of the hydrothermal alteration assemblages switches from relatively reduced pyrrhotite-pyrite to relatively oxidized magnetite

  7. Mercury deposition in snow near an industrial emission source in the western U.S. and comparison to ISC3 model predictions

    USGS Publications Warehouse

    Abbott, M.L.; Susong, D.D.; Krabbenhoft, D.P.; Rood, A.S.

    2002-01-01

    Mercury (total and methyl) was evaluated in snow samples collected near a major mercury emission source on the Idaho National Engineering and Environmental Laboratory (INEEL) in southeastern Idaho and 160 km downwind in Teton Range in western Wyoming. The sampling was done to assess near-field (<12 km) deposition rates around the source, compare them to those measured in a relatively remote, pristine downwind location, and to use the measurements to develop improved, site-specific model input parameters for precipitation scavenging coefficient and the fraction of Hg emissions deposited locally. Measured snow water concentrations (ng L-1) were converted to deposition (ug m-2) using the sample location snow water equivalent. The deposition was then compared to that predicted using the ISC3 air dispersion/deposition model which was run with a range of particle and vapor scavenging coefficient input values. Accepted model statistical performance measures (fractional bias and normalized mean square error) were calculated for the different modeling runs, and the best model performance was selected. Measured concentrations close to the source (average = 5.3 ng L-1) were about twice those measured in the Teton Range (average = 2.7 ng L-1) which were within the expected range of values for remote background areas. For most of the sampling locations, the ISC3 model predicted within a factor of two of the observed deposition. The best modeling performance was obtained using a scavenging coefficient value for 0.25 ??m diameter particulate and the assumption that all of the mercury is reactive Hg(II) and subject to local deposition. A 0.1 ??m particle assumption provided conservative overprediction of the data, while a vapor assumption resulted in highly variable predictions. Partitioning a fraction of the Hg emissions to elemental Hg(0) (a U.S. EPA default assumption for combustion facility risk assessments) would have underpredicted the observed fallout.

  8. Hydrothermal modification of host rock geochemistry within Mo-Cu porphyry deposits in the Galway Granite, western Ireland

    NASA Astrophysics Data System (ADS)

    Tolometti, Gavin; McCarthy, Will

    2016-04-01

    Hydrothermal alteration of host rock is a process inherent to the formation of porphyry deposits and the required geochemical modification of these rocks is regularly used to indicate proximity to an economic target. The study involves examining the changes in major, minor and trace elements to understand how the quartz vein structures have influenced the chemistry within the Murvey Granite that forms part of the 380-425Ma Galway Granite Complex in western Ireland. Molybdenite mineralisation within the Galway Granite Complex occurred in close association with protracted magmatism at 423Ma, 410Ma, 407Ma, 397Ma and 383Ma and this continues to be of interest to active exploration. The aim of the project is to characterize hydrothermal alteration associated with Mo-Cu mineralisation and identify geochemical indicators that can guide future exploration work. The Murvey Granite intrudes metagabbros and gneiss that form part of the Connemara Metamorphic complex. The intrusion is composed of albite-rich pink granite, garnetiferous granite and phenocrytic orthoclase granite. Minor doleritic dykes post-date the Murvey Granite, found commonly along its margins. Field mapping shows that the granite is truncated to the east by a regional NW-SE fault and that several small subparallel structures host Mo-Cu bearing quartz veins. Petrographic observations show heavily sericitized feldspars and plagioclase and biotite which have undergone kaolinization and chloritisation. Chalcopyrite minerals are fine grained, heavily fractured found crystallized along the margins of the feldspars and 2mm pyrite crystals. Molybdenite are also seen along the margins of the feldspars, crystallized whilst the Murvey Granite cooled. Field and petrographic observations indicate that mineralisation is structurally controlled by NW-SE faults from the selected mineralization zones and conjugate NE-SW cross cutting the Murvey Granite. Both fault orientations exhibit quartz and disseminated molybdenite

  9. Geochemistry of the Yangla volcanic rocks and its relationship to Cu mineralization in the Yangla copper deposit, western Yunnan, China

    NASA Astrophysics Data System (ADS)

    Yang, Xian; Liu, Jiajun; Zhai, Degao; Han, Siyu; Wang, Huan; Yang, Longbo; Huo, Dongliang

    2012-10-01

    The Yangla copper deposit is a recently discovered, giant copper deposit with an estimated Cu reserve of about 1,200,000 tons. Development is now underway. Previous studies have reported that the Yangla copper deposit is a VMS-type deposit related to the Yangla volcanic rocks. Volcanic bulk-rock analyses shows high contents of Si (49.3%-58.7%), Na2O (Na2O = 3.3%-4.9%), MgO (MgO = 3.7%-8.6%), and CaO(CaO = 6.8%-9.0%), low TiO2 (TiO2 = 0.9%-2.1%) and K2O(K2O = 0.2%-1.4%) contents. The geochemistry of the volcanic represent forearc basalts. Four molybdenites samples from the ore bodies in the deposit yield Re-Os model ages ranging from 229.7 ± 3.3 Ma to 233 ± 3.4 Ma. The REE distribution patterns and the primitive-mantle-normalized trace element patterns of the volcanic rocks are similar to the ores, indicating the Yangla copper deposit are closely associated with the Yangla volcanic rocks. The results contribute to our understanding of the genesis of the Yangla copper deposit and will guide further exploration in the region.

  10. Application of geologic-mathematical 3D modeling for complex structure deposits by the example of Lower- Cretaceous period depositions in Western Ust - Balykh oil field (Khanty-Mansiysk Autonomous District)

    NASA Astrophysics Data System (ADS)

    Perevertailo, T.; Nedolivko, N.; Prisyazhnyuk, O.; Dolgaya, T.

    2015-11-01

    The complex structure of the Lower-Cretaceous formation by the example of the reservoir BC101 in Western Ust - Balykh Oil Field (Khanty-Mansiysk Autonomous District) has been studied. Reservoir range relationships have been identified. 3D geologic- mathematical modeling technique considering the heterogeneity and variability of a natural reservoir structure has been suggested. To improve the deposit geological structure integrity methods of mathematical statistics were applied, which, in its turn, made it possible to obtain equal probability models with similar input data and to consider the formation conditions of reservoir rocks and cap rocks.

  11. Source versus depositional controls on sandstone composition in a foreland basin: The El Imperial Formation (Mid Carboniferous-Lower Permian), San Rafael basin, western Argentina

    SciTech Connect

    Espejo, E.S. ); Lopez-Gamundi, O.R. . Frontier Exploration Dept.)

    1994-01-01

    The El Imperial Formation (mid-Carboniferous-Lower Permian) constitutes a progradational sandstone-rich succession deposited in the San Rafael foreland basin of western Argentina. Four facies associations have been identified: a basal glacial marine association, a shallow marine association, a deltaic association, and an uppermost fluvial association. Sand-prone deposits in the deltaic association, a shallow marine association, a deltaic association, and an uppermost fluvial association. Sand-prone deposits in the deltaic association are represented by prodelta and delta-front shales and subordinate fine sandstones (Facies A), deltaic platform, wave-reworked channel mouth-bar sandstones (Facies B), and fluvial-dominated distributary channel sandstones (Facies C). Analysis of framework grains of sandstone samples from Facies B and C shows two distinct mineral assemblages or petrofacies. The quartzose petrofacies is characterized by high contents of quartz and low percentages of feldspar and lithic grains. The quartzolithic petrofacies shows an increase in labile components, in particular lithic fragments, and a concomitant decrease in quartz. The quartzolithic petrofacies shows a source signature. Average detrital modes of sandstones from this petrofacies are similar to those from overlying fluvial sandstones. All wave-reworked, channel mouth-bar sandstones (Facies B) correspond compositionally to the quartzose petrofacies, whereas detrital modes from the distributary-channel sandstones (Facies C) fall into the quartzolithic petrofacies. This correspondence between depositional environment and petrofacies suggests a strong depositional influence on composition (depositional signature). Abrasion (mechanical breakdown) by wave action in shallow marine environments accounts for the quartz-rich nature and paucity of labile grains in the quartzose petrofacies.

  12. Comparison of mercury mass loading in streams to atmospheric deposition in watersheds of Western North America: Evidence for non-atmospheric mercury sources.

    PubMed

    Domagalski, Joseph; Majewski, Michael S; Alpers, Charles N; Eckley, Chris S; Eagles-Smith, Collin A; Schenk, Liam; Wherry, Susan

    2016-10-15

    Annual stream loads of mercury (Hg) and inputs of wet and dry atmospheric Hg deposition to the landscape were investigated in watersheds of the Western United States and the Canadian-Alaskan Arctic. Mercury concentration and discharge data from flow gauging stations were used to compute annual mass loads with regression models. Measured wet and modeled dry deposition were compared to annual stream loads to compute ratios of Hg stream load to total Hg atmospheric deposition. Watershed land uses or cover included mining, undeveloped, urbanized, and mixed. Of 27 watersheds that were investigated, 15 had some degree of mining, either of Hg or precious metals (gold or silver), where Hg was used in the amalgamation process. Stream loads in excess of annual Hg atmospheric deposition (ratio>1) were observed in watersheds containing Hg mines and in relatively small and medium-sized watersheds with gold or silver mines, however, larger watersheds containing gold or silver mines, some of which also contain large dams that trap sediment, were sometimes associated with lower load ratios (<0.2). In the non-Arctic regions, watersheds with natural vegetation tended to have low ratios of stream load to Hg deposition (<0.1), whereas urbanized areas had higher ratios (0.34-1.0) because of impervious surfaces. This indicated that, in ecosystems with natural vegetation, Hg is retained in the soil and may be transported subsequently to streams as a result of erosion or in association with dissolved organic carbon. Arctic watersheds (Mackenzie and Yukon Rivers) had a relatively elevated ratio of stream load to atmospheric deposition (0.27 and 0.74), possibly because of melting glaciers or permafrost releasing previously stored Hg to the streams. Overall, our research highlights the important role of watershed characteristics in determining whether a landscape is a net source of Hg or a net sink of atmospheric Hg. PMID:27015962

  13. Atmospherically deposited PBDEs, pesticides, PCBs, and PAHs in Western US National Park fish: Concentrations and consumption guidelines

    EPA Science Inventory

    Concentrations of polybrominated diphenyl ethers (PBDEs), pesticides, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons were measured in 136 fish from 14 remote lakes in 8 western U.S. National Parks/Preserves between 2003 and 2005 and compared to human and w...

  14. The Paleozoic Dust Bowl: Dust Deposition in Tropical Western Pangaea (Midcontinent U.S.) at the Terminus of the Late Paleozoic Ice Age

    NASA Astrophysics Data System (ADS)

    Soreghan, G. S.; Heavens, N. G.; Benison, K. C.; Soreghan, M. J.; Mahowald, N. M.; Foster, T.; Zambito, J.; Sweet, A.; Kane, M.

    2012-12-01

    Atmospheric dust is well recognized and studied as both an archive and agent of climate change in Earth's relatively recent past. Archives of past dust include loess deposits and dust recovered from ocean- and ice-cores. Dust remains poorly known in Earth's past prior to the Cenozoic, but is increasingly recognized in the form of paleo-loess deposits, and (epeiric) marine strata that accumulated isolated from fluvio-deltaic influx. Here, we report on the growing recognition of voluminous dust deposits preserved in the Permian record of the U.S. Midcontinent (western tropical Pangaea). Fine-grained redbeds predominate in Permian strata throughout the U.S. Midcontinent, but notably in a swath extending from Oklahoma through South Dakota. These units consist predominantly of red mudstone and siltstone in commonly massive units, but sedimentary structures and bedding that signal aqueous processes (e.g. laminations, ripples) have led most to infer deltaic or tidal deposition. The absence of channel systems to deliver the sediment, as well as the predominantly massive and laterally continuous character and the uniform fine grain size signal wind transport, implying that these units record sustained dust deposition overprinted at times by sub-aqueous deposition in lakes, including ephemeral saline and acid lakes that led to evaporite cementation. Detrital zircon geochronology indicates that much of the dust originated in the relatively distant Appalachian-Ouachita orogenic systems, which formed part of the central Pangaean mountains (CPM), the collisional zone that sutured the supercontinent. Within the Anadarko basin of Oklahoma, Permian redbeds record >2 km of predominantly dust deposition, some of the thickest dust deposits yet documented in Earth's record. Yet the tropical setting is remarkably non-uniformitarian, as much Quaternary loess occurs in mid- to high-latitude regions, commonly linked to glacial genesis. We are currently investigating with both data and

  15. Constraints on the composition of ore fluids and implications for mineralising events at the Cleo gold deposit, Eastern Goldfields Province, Western Australia

    USGS Publications Warehouse

    Brown, S.M.; Johnson, C.A.; Watling, R.J.; Premo, W.R.

    2003-01-01

    The Cleo gold deposit, 55 km south of Laverton in the Eastern Goldfields Province of Western Australia, is characterised by banded iron-formation (BIF)-hosted ore zones in the gently dipping Sunrise Shear Zone and high-grade vein-hosted ore in the Western Lodes. There is evidence that gold mineralisation in the Western Lodes (which occurred at ca 2655 Ma) post-dates the majority of displacement along the Sunrise Shear Zone, but it remains uncertain if the ore in both structures formed simultaneously or separately. Overall, the Pb, Nd, Sr, C. O and S isotopic compositions of ore-related minerals from both the Western Lodes and ore zones in the Sunrise Shear Zone are similar. Early low-salinity aqueous-carbonic fluids and late high-salinity fluids with similar characteristics are trapped in inclusions in quartz veins from both the Sunrise Shear Zone and the Western Lodes. The early CO2, CO2-H2O, and H2O- dominant inclusions are interpreted as being related to ore formation, and to have formed from a single low-salinity aqueous-carbonic fluid as a result of intermittent fluid immiscibility. Homogenisation temperatures indicate that these inclusions were trapped at approximately 280??C and at approximately 4 km depth, in the deeper epizonal range. Differences between the ore zones are detected in the trace-element composition of gold samples, with gold from the Sunrise Shear Zone enriched in Ni, Pb, Sn, Te and Zn, and depleted In As, Bi, Cd, Cu and Sb, relative to gold from the Western Lodes. Although there are differences in gold composition between the Sunrise Shear Zone and Western Lodes, and hence the metal content of ore fluids may have varied slightly between the different ore zones, no other systematic fluid or solute differences are detected between the ore zones. Given the fact that the ore fluids in each zone have very similar bulk properties, the considerable differences in gold grade, sulfide mineral abundance, and ore textures between the two ore zones

  16. Gold mineralisation at the Lady Bountiful Mine, Western Australia: An example of a granitoid-hosted Archaean lode gold deposit

    NASA Astrophysics Data System (ADS)

    Cassidy, K. F.; Bennett, J. M.

    1993-12-01

    The Lady Bountiful granitoid-hosted lode gold deposit, located in the mid-greenschist facies metamorphosed Ora Banda greenstone sequence, is hosted predominantly by the late-tectonic Liberty Granodiorite. Gold mineralisation is localised along quartz-veined, sinistral, brittle fault-zone(s) that transect the boundary between the Liberty Granodiorite and Mt Pleasant sill. Quartz vein textures indicate two stages of a single gold-related vein-development event, with high-grade gold mineralisation restricted to the second stage. Ore minerals include pyrite, chalcopyrite, pyrrhotite, galena, sphalerite, Au-Ag-Bi-Pb-tellurides, and native gold. Fluid infitration has resulted in narrow (<1 m) bleached wallrock alteration envelopes to the fault zones comprising albite-K-mica ±chlorite±calcite±rutile assemblages. Temperature-pressure conditions varied from Stage I (300°±50°C, ≈2 kbar) to Stage II (250°±50°C, ≈0.5 to 2 kbar), with the hydrothermal fluid in both stages characterised by X(CO2)≤0.15 and moderate salinity (≈1.28 m NaCl). Intermittent phase separation of Stage II mineralising fluids, initiated by pressure fluctuations in dilational sites, and/or fluid-dominated fluid: wallrock interaction, are invoked as the dominant depositional mechanisms. The granitoid-hosted Lady Bountiful lode gold deposit shares many features with other granitoid-hosted lode gold deposits in the Yilgarn Craton and the Superior Province. Granitoid-hosted lode gold deposits, such as the Lady Bountiful deposit, provide additional evidence that the dominant control on the localisation of gold mineralisation within a granitoid host is structure, with competency contrasts playing a significant role. Furthermore, the hydrothermal wallrock alteraction and orefluid chemistry characteristics of the granitoid-hosted lode gold deposits are comparable to those established for greenstone-hosted lode gold mineralisation.

  17. Reconstruction of Holocene coastal depositional environments based on sedimentological and palaeontological analyses, Zakynthos Island, Western Greece Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Avramidis, Pavlos; Iliopoulos, George; Papadopoulou, Penelope; Nikolaou, Konstantinos; Kontopoulos, Nikolaos; Wijngaarden, Gert

    2014-05-01

    Zakynthos Island is one of the most seismically active regions in Europe and the Holocene coastal depositional environments were influenced both by tectonic activity and sea level rise. In the present study detailed sedimentological, palaeontological and 14C dating analyses were used in order to reconstruct the Holocene coastal depositional environments as well as the different rates of sedimentation, based on data from three cores up to 30 m deep. The results of the analyses indicate changes in depositional environments from marine to brackish lagoonal and lagoon / barrier systems with temporary intrusions of marine water via storms or tsunamigenic events. High sedimentation rates in coastal areas of Zakynthos Island correspond well to the most widespread Holocene warm and humid phases. The interpretation of the sedimentological environments reveals that Zakynthos Island before 8300 BP was constituted by two islands, where the present southern part of the island was separated from the northern one by a shallow and narrow sea channel.

  18. Characteristics and genesis of mineral deposits in East Ujimqin Banner, western segment of the Great Xing'an Mountains, NE China

    NASA Astrophysics Data System (ADS)

    Zhang, Wanyi; Nie, Fengjun; Liu, Shuwen; Zuo, Liyan; Yao, Xiaofeng; Jia, Delong; Liu, Jiangtao

    2015-01-01

    The East Ujimqin Banner, located in the western segment of the Great Xing'an Mountains, NE China, has undergone a long and multi-stage tectonic evolution, which has resulted in significant Fe-Ag-Pb-Zn-Au-Cu-Mo deposits. There are two main types of mineralization: vein and skarn types. The Jilinbaolige and Aerhada vein deposits, and the Chagan Obo and Chaobuleng skarn-type deposits are four typical deposits in this area. The vein deposits mainly occur as veins with hydrothermal alteration in fractures within pre-mineralization clastic rocks and felsic volcanic rocks. The skarn-type deposits always show a temporal and spatial relationship with Mesozoic granite intruded into Paleozoic limestone. The sulfur isotope data from the sulfides in these four deposits have a very narrow range (+1‰ to +8‰), suggesting that most were derived from magma. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios range from 17.949 to 18.529, 15.370 to 15.691 and 37.653 to 38.460 respectively, indicating that the metals derive mainly from the mantle source. In the diagrams 207Pb/204Pb vs. 206Pb/204Pb and 208Pb/204Pb vs. 206Pb/204Pb, the points of lead isotope of the sulfide ores are very near or coincide to the K-feldspar, indicating that the ore-forming materials sources have the genetic relationship. It seems that there are four key factors controlling the mineralization styles in this district: the tectonic setting, magmatic activity, wall rocks, and structures. The superposition of multi-stage tectonism from a Mesozoic extensional setting on a Paleozoic subduction setting provided a remobilization and enrichment mechanism for the ore-forming elements. The magmatic activities were sources of metals and fluids, and drove them to the mineralization sites. The wall rocks are key factors for mineralization styles. When metal-bearing fluid flows into clastic rocks and felsic volcanic rocks, the mineralization is mainly vein type, and mineralization in limestone is mainly skarn type. NE

  19. The largest Au deposits in the St Ives Goldfield (Yilgarn Craton, Western Australia) may be located in a major Neoarchean volcano-sedimentary depo-centre

    NASA Astrophysics Data System (ADS)

    McGoldrick, K. L.; Squire, R. J.; Cas, R. A. F.; Briggs, M.; Tunjic, J.; Allen, C. M.; Campbell, I. H.; Hayman, P. C.

    2013-10-01

    The largest Neoarchean gold deposits in the world-class St Ives Goldfield, Western Australia, occur in an area known as the Argo-Junction region (e.g. Junction, Argo and Athena). Why this region is so well endowed with large deposits compared with other parts of the St Ives Goldfield is currently unclear, because gold deposits at St Ives are hosted by a variety of lithologic units and were formed during at least three different deformational events. This paper presents an investigation into the stratigraphic architecture and evolution of the Argo-Junction region to assess its implications for gold metallogenesis. The results show that the region's stratigraphy may be subdivided into five regionally correlatable packages: mafic lavas of the Paringa Basalt; contemporaneously resedimented feldspar-rich pyroclastic debris of the Early Black Flag Group; coarse polymictic volcanic debris of the Late Black Flag Group; thick piles of mafic lavas and sub-volcanic sills of the Athena Basalt and Condenser Dolerite; and the voluminous quartz-rich sedimentary successions of the Early Merougil Group. In the Argo-Junction region, these units have an interpreted maximum thickness of at least 7,130 m, and thus represent an unusually thick accumulation of the Neoarchean volcano-sedimentary successions. It is postulated that major basin-forming structures that were active during deposition and emplacement of the voluminous successions later acted as important conduits during mineralisation. Therefore, a correlation exists between the location of the largest gold deposits in the St Ives Goldfield and the thickest parts of the stratigraphy. Recognition of this association has important implications for camp-scale exploration.

  20. Paleozoic sedimentary rocks in the Red Dog Zn-Pb-Ag district and vicinity, western Brooks Range, Alaska: provenance, deposition, and metallogenic significance

    USGS Publications Warehouse

    Slack, John F.; Dumoulin, Julie A.; Schmidt, J.M.; Young, L.E.; Rombach, Cameron

    2004-01-01

    The distribution and composition of Paleozoic strata in the western Brooks Range may have played a fundamental role in Zn-Pb mineralization of the Red Dog district. In our model, deposition and early lithification of biogenic chert and bedded siliceous rocks in the upper part of the Kuna Formation served as a regional hydrologic seal, acting as a cap rock to heat and hydrothermal fluids during Late Mississippian base-metal mineralization. Equally important was the iron-poor composition of black shales of the Kuna Formation (i.e., low Fe/Ti ratios), which limited synsedimentary pyrite formation in precursor sediments, resulting in significant H2S production in pore waters through the interaction of aqueous sulfate with abundant organic matter. This H2S may have been critical to the subsurface deposition of the huge quantities of Zn and Pb in the district. On the basis of this model, we propose that low Fe/Ti and S/C ratios in black shale sequences are potential basin-scale exploration guides for giant sediment-hosted, stratiform Zn-Pb-Ag deposits.

  1. Field and ASTER imagery data for the setting of gold mineralization in Western Allaqi-Heiani belt, Egypt: A case study from the Haimur deposit

    NASA Astrophysics Data System (ADS)

    Zoheir, Basem; Emam, Ashraf

    2014-11-01

    Although associated with carbonatized/listvenitized ophiolites and thrust structures, the morphology and internal structures of the auriferous quartz veins in the Haimur deposit suggest mineralization concurrent with NE-SW dextral brittle-ductile shear zones. The latter are attributed to intense transpression regime and are associated with (N)NE-trending tight to isoclinals folds that deform the early accretionary structures. Image processing techniques applicable to the Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) data are used for mapping structures and hydrothermal alteration associated with the Haimur deposit. The automated lineament extraction by LINE module on high resolution ASTER imagery provides efficient data for potential dilation loci. Emphasis is placed on reliability of mineral indices extracted from the ASTER band ratios for identification of possibly mineralized alteration zones associated with NE-trending shear zones. Field and remote sensing data, together with the structural fabrics along the lode-associated shear zones clearly constrain on the genetic relationship between the Haimur gold deposit and post-accretionary transpression/shearing. We conclude that hydrothermal alteration zones that are confined to tightly enfolded ophiolites and transpressive shear zones along the Western Allaqi-Heiani belt are most potential targets for new exploration plans.

  2. Geophysical Exploration of Disseminated and Stockwork deposits associated with plutonic intrusive: A Case study in the eastern flank of the western Cordillera, Colombia

    NASA Astrophysics Data System (ADS)

    Hernandez, O.; Alexander, G. C.; Pintor, I. M.

    2011-12-01

    Disseminated deposit exploration in the tropics suffers from difficult geological mapping due to thick vegetation, lack of rock outcrop, and extensive but variable saprolitic weathering. Geophysical exploration of these deposits normally includes magnetic, induced polarization and gamma ray spectrometry surveys. The largest RTP Total field magnetic anomaly highs are usually associated with the diorite porphyry intrusive bodies. Normally, diorites are less magnetic than the basaltic rocks. Therefore, where the magnetic anomaly highs are related to the intrusions they can be explained by the intensive mineralization of basic metals including magnetite that are associated with the porphyry intrusions. Regularly, the magnetic anomaly gradients help to delineate local discontinuities that can be interpreted as local faults and joints that can be mineralized. The gamma ray spectrometry is useful to determine the anomalous concentration of Potassium, Uranium and Thorium that can be interpreted in terms of alteration halos and linear discontinuities. The statistical analysis of the data also can determine the intermediate intrusive / extrusive nature of the porphyry intrusions. The use of gamma ray spectrometry helps to determine the concentration of elemental potassium, regardless of the associated potassium mineral species, enabling alteration mapping in a geological setting related to volcanic-associated massive sulphide base metals and gold. The induced polarization survey is useful in outlining sulphide distribution in porphyry deposits related to chargeability anomaly highs. The preliminary results of the geophysical exploration program of the eastern flank of the Western Cordillera in the Andes Mountains of Colombia are discussed.

  3. Breastfeeding practices in Chengdu, Sichuan, China.

    PubMed

    Guldan, G S; Zhang, M; Zeng, G; Hong, J; Yang, Y

    1995-03-01

    Barriers to increased breastfeeding rates in Chengdu, Sichuan were investigated in 1992 and 1993. Responses of focus groups showed that ignorance about breastfeeding and belief that the mother's milk was inadequate, and lack of support from their families, places of employment, and the health system acted as barriers to the women's breastfeeding their infants up to the age of four to six months. Subsequently, 363 mothers of 4- to 12-month-old Chengdu infants were surveyed. Although most mothers in both studies said breastmilk was the best food for their infant up to age of four to six months, only about half of the mothers breastfed for longer than one month. Both studies showed that infants who roomed with their mothers after birth were more likely to have been put to their mother's breast earlier, fed colostrum, breastfed somewhat longer, and exclusively breastfed for a somewhat longer period, although their mothers' infant feeding knowledge did not differ. The researchers conclude that Chengdu health workers should teach parents and parents-to-be more about breastfeeding, and that rooming-in be expanded in Chengdu hospitals. PMID:7718100

  4. Geological, mineralogical and geochemical characteristics of zeolite deposits associated with borates in the Bigadiç, Emet and Kirka Neogene lacustrine basins, western Turkey

    NASA Astrophysics Data System (ADS)

    Gündogdu, M. N.; Yalçin, H.; Temel, A.; Clauer, N.

    1996-09-01

    The Bigadiç, Emet and Kirka lacustrine basins of western Turkey may be considered as Tibet-type graben structures that were developed during the Miocene within the Izmir-Ankara suture zone complex. The volcanic-sedimentary successions of these basins are made up of mudstone, carbonate (limestone and dolomite) and detrital rocks, and also of crystal or vitric tuffs about 135 to 200 m thick. The Degirmenli (Bigadiç), Emirler (Bigadiç) Köpenez (Emet) and Karaören (Kirka) tuffs constituting the zeolite deposits are situated beneath four borate deposits (colemanite, ulexite, borax). The most abundant diagenetic silicate minerals are K- and Ca-clinoptilolites in the zeolite deposits, and Li-rich trioctahedral smectites (stevensite, saponite and hectorite) and K-feldspar in the borate deposits. In the Degirmenli, Emirler, Köpenez and Karaören deposits, the following diagenetic facies were developed from rhyolitic glasses rich in K and poor in Na: (glass+smectite), (K-clinoptilolite+opal-CT), (Ca-clinoptilolite+K-feldspar±analcime± quartz) and (K-feldspar+analcime+quartz). K-feldspar which is also rarely associated with phillipsite (Karaören) and heulandite (Degirmenli and Karaören), succeeds clinoptilolite and precedes analcime in these diagenetic facies where dioctahedral smectites, opal-CT and quartz are the latest minerals. No diagenetic transformations exist between clinoptilolite, K-feldspar and analcime that were formed directly from glass. The lateral facies distributions resulted from the differences in salinity and pH of pore water trapped during deposition of the tuffs, but vertical distributions in vitric tuffs seem to have been controlled by the glass/liquid ratio of the reacting system and the permeability or diffusion rate of alkali elements. The Bigadiç, Emet and Kirka zeolite deposits which were formed in saline basins rich in Ca and Mg ions, show similar chemical changes, i.e. loss of alkalis and gain in alkaline-earth elements that have taken

  5. Uranium-series ages of corals and coexisting phosphate deposits on Pelsaert Reef Complex, Houtman-Abrolhos Islands, Western Australia

    NASA Astrophysics Data System (ADS)

    Veeh, H. Herbert; France, Roy E.

    1988-09-01

    An unusually well-defined association between guano-derived phosphate rock (apatite) and coral carbonates on Pelsaert Island has provided an opportunity to test uranium-series dating methods as applied to insular phosphorites. The phosphate deposit, which is bracketed by late Pleistocene and Holocene corals with {230Th}/{234U} ages of 120,000 and 4700 yr B.P., respectively, has {230Th}/{234U} ages ranging from 85,000 to 112,000 yr B.P. The mutually consistent results suggest that phosphate deposition commenced soon after the peak of the last interglaciation and has been largely controlled by sea-level fluctuations and probably other factors associated with late Quaternary climate in this area.

  6. Stratigraphy, sedimentology, paleontology, and paleomagnetism of Pliocene-early Pleistocene lacustrine deposits in two cores from western Utah

    USGS Publications Warehouse

    Thompson, R.S.; Oviatt, Charles G.; Roberts, A.P.; Buchner, J.; Kelsey, R.; Bracht, C.J.; Forester, R.M.; Bradbury, J.P.

    1995-01-01

    The paleoclimatic history of western Utah is being investigated as part of the USGS Global Change and Climate History Program studies of long-term climatic changes in the western United States. The initial objective of the study is to document the environmental conditions during the mid-Pliocene period of warmer-than-modern global climates (the focus of the USGS Pliocene Research, Interpretation, and Synoptic Mapping [PRISM] project). The investigation also seeks to determine how and when these conditions gave way to the late Quaternary pattern of climatic variations (in which short periods of very moist climates have been separated by long periods of arid conditions). This is a collaborative project involving specialists from the USGS, Kansas State University, and the University of California-Davis in paleontology (Thompson, Buchner, Forester, Bradbury), stratigraphy and sedimentology (Oviatt, Kelsey, Bracht), and paleomagnetism and environmental magnetism (Roberts). The data presented herein represent preliminary findings of the analyses of two cores of Pliocene and early Pleistocene sediments from the eastern Great Basin.

  7. Ca/Mg ratio and depositional cycles in marine upper Absheron substage succession in the Western flank of the South Caspian depression

    NASA Astrophysics Data System (ADS)

    Amirov, E.

    2009-04-01

    The Caspian Sea, the largest land locked basin in the world, isolated from ParaTethys at the end of Messinian. Since that time sedimentation there took place under conditions of isolated basin temporarily connected with Black Sea in Upper Pliocene (Akchagyl). The aim of this work was the reconstruction of paleotemperature of South Caspian basin in marine upper Absheron substage time by using Ca/Mg ratio from ostracoda carapaces. The results of the field works on exposures of the Lower Pleistocene deposits located in the Western flank of the South Caspian depression (Shikhov outcrop) demonstrated the high-frequency cyclicity in sedimentation accompanied by rapid lateral and vertical depositional environmental change. It is possible to observe several depositional sequences developed from low stand system tract to transgressive and high stand system tract. The quantitative changes of ostracoda composition for each interbed depending on paleotemperature fluctuations, in detail point out the tendency of increasing and decreasing of Ca/Mg ratio in carapaces as indicator of paleotemperature. It was clearly recognized that Ca/Mg ratio increases in high stand system tract and decreases in regressive systems tracts. As well as was observed positive correlation tendency between amount of ostracoda carapaces and Ca/Mg ratio, in most cases with increasing of Ca/Mg ratio, amount of ostarcoda carapaces increase and with decreasing of Ca/Mg ratio, amount of ostracoda carapaces decrease. Just in some cases we can observe invert correlation. Carried out biogeochemical analyses have shown that amount of the studied elements, including Ca and Mg considerably varies in a section, which reflects the change in paleotemperature and depositional setting during accumulation of sediments.

  8. SHRIMP U-Pb ages of xenotime and monazite from the Spar Lake red bed-associated Cu-Ag deposit, western Montana: Implications for ore genesis

    USGS Publications Warehouse

    Aleinikoff, John N.; Hayes, Timothy S.; Evans, Karl V.; Mazdab, Frank K.; Pillers, Renee M.; Fanning, C. Mark

    2012-01-01

    Xenotime occurs as epitaxial overgrowths on detrital zircons in the Mesoproterozoic Revett Formation (Belt Supergroup) at the Spar Lake red bed-associated Cu-Ag deposit, western Montana. The deposit formed during diagenesis of Revett strata, where oxidizing metal-bearing hydrothermal fluids encountered a reducing zone. Samples for geochronology were collected from several mineral zones. Xenotime overgrowths (1–30 μm wide) were found in polished thin sections from five ore and near-ore zones (chalcocite-chlorite, bornite-calcite, galena-calcite, chalcopyrite-ankerite, and pyrite-calcite), but not in more distant zones across the region. Thirty-two in situ SHRIMP U-Pb analyses on xenotime overgrowths yield a weighted average of 207Pb/206Pb ages of 1409 ± 8 Ma, interpreted as the time of mineralization. This age is about 40 to 60 m.y. after deposition of the Revett Formation. Six other xenotime overgrowths formed during a younger event at 1304 ± 19 Ma. Several isolated grains of xenotime have 207Pb/206Pb ages in the range of 1.67 to 1.51 Ga, and thus are considered detrital in origin. Trace element data can distinguish Spar Lake xenotimes of different origins. Based on in situ SHRIMP analysis, detrital xenotime has heavy rare earth elements-enriched patterns similar to those of igneous xenotime, whereas xenotime overgrowths of inferred hydrothermal origin have hump-shaped (i.e., middle rare earth elements-enriched) patterns. The two ages of hydrothermal xenotime can be distinguished by slightly different rare earth elements patterns. In addition, 1409 Ma xenotime overgrowths have higher Eu and Gd contents than the 1304 Ma overgrowths. Most xenotime overgrowths from the Spar Lake deposit have elevated As concentrations, further suggesting a genetic relationship between the xenotime formation and Cu-Ag mineralization.

  9. Spatial correlation of mantle heterogeneities beneath the south-western part of the East-European platform with oil-gas deposits and basic-ultrabasic magmatism.

    NASA Astrophysics Data System (ADS)

    Shumlyanska, L.

    2009-04-01

    Velocity model of mantle beneath the south-western margin of the East-European platform demonstrates its heterogeneous structure. Accordingly to the crustal structures above mantle heterogeneities were defined as: Volyno-Podolian, Ros-Bug, Ingulo-Middlednieper, Periasov, Volyno-Podolian plate, Peridnister, Peri-Blacksea, Chernigov, Dnieper, Donetsk, Eastern-Blacksea, Crimea, Western-Blacksea. These blocks are defined as regions differing in the depth of the bottom of the velocity layers that characterize velocity structure of the mantle and in the velocity characteristics of these layers. Layer boundaries are defined as intersection with 1-d reference model. Areas with residuals >0.0 km/s are considered as high-velocity while areas with residuals <0.0 km/s are defined as low-velocity. There is a spatial correlation between boundaries of mantle blocks and location of oil-gas deposits and basic-ultrabasic magmatism. Some of the mantle blocks (Peri-Blacksea, Eastern-Blacksea, Crimea, Western-Blacksea, Periasov, Volyno-Podolian plate, Peridnister) that situated beneath margin of the platform and others (Chernigov, Dnieper, Donetsk) that situated beneath the Dnieper-Donetsk depression display spatial correlation with crust-seated oil-gas provinces - Crimean, Volyno-Podolian, Pericarpathian, and Dnieper-Donetsk, correspondingly. Oil-gas field have a propensity for boundaries of mentioned above mantle blocks. Those mantle blocks (Volyno-Podolian, Ros-Bug, Ingulo-Middlednieper, Periasov) that located under the Ukrainian shield display spatial correlation with basic-ultrabasic magmatism that confined to the blocks boundaries. Age of this magmatism varies from Paleoproterozoic to Neoproterozoic. Velocity model of the south-western part of the East-European platform obtained by the method of seismic tomography employing methodology of the Taylor's approximation of the solution of the task of seismic tomography of the times of arrivals of P-waves developed by V.S. Geyko [1

  10. Imprint of North-Atlantic abrupt climate changes on western European loess deposits as viewed in a dust emission model

    NASA Astrophysics Data System (ADS)

    Sima, Adriana; Rousseau, Denis-Didier; Kageyama, Masa; Ramstein, Gilles; Schulz, Michael; Balkanski, Yves; Antoine, Pierre; Dulac, François; Hatté, Christine

    2009-12-01

    Western European loess sequences of the last glaciation (˜100,000-15,000 years BP) exhibit strong, cyclic variations of the sedimentation rate, which are coeval to the Greenland stadial/interstadial cycles and the Heinrich events. These North-Atlantic rapid climate changes appear, thus, as a potential cause for the sedimentation variations, via changes in dust intensity cycle. Here we make a first step in testing this hypothesis, by modelling the impact of the North-Atlantic abrupt climate variations on dust emission. Our dust emission calculations use meteorological fields generated by the LMDZ atmospheric general circulation model at a resolution down to 60 km over Western Europe. Three numerical experiments are run, representing a Greenland stadial, an interstadial and a Heinrich event. Orbital parameters and ice-sheet configuration correspond to conditions from Marine Isotope Stage 3 (˜60,000-25,000 years BP), a period characterized by strong millennial-scale climate variability. The only differences we impose in the boundary conditions regard the North-Atlantic surface temperature and sea-ice cover in the latitudinal band 30°-63°N. The changes in wind, precipitation, soil moisture and snow cover from one simulated state to another result in small differences in dust emission intensity. In contrast, when the inhibition of the aeolian erosion by vegetation is taken into account, the dust fluxes for the cold climate states (Greenland stadial and Heinrich event) become generally more than twice higher than those for the relatively warmer Greenland interstadial, in agreement with the loess data. These results support the hypothesis that the North-Atlantic millennial-scale variability is imprinted in Western European loess profiles, and point to vegetation changes as the main factor responsible for millennial-scale sedimentation variations. An analysis for the English Channel and southern North Sea areas, major potential dust sources, shows that the seasonality

  11. Hydrothermal alteration, ore fluid characteristics, and gold depositional processes along a trondhjemite-komatiite contact at Tarmoola, Western Australia

    USGS Publications Warehouse

    Duuring, P.; Hagemann, S.G.; Cassidy, K.F.; Johnson, C.A.

    2004-01-01

    Tarmoola is a structurally controlled Archean orogenic gold deposit hosted in greenschist facies metamorphosed komatiite and trondhjemite in the Leonora district of the Eastern Goldfields province, Yilgarn craton. High-grade (>1 g/t Au) orebodies are located in komatiite wall rock adjacent to the eastern and northeastern margins of the asymmetrical, north-south-striking, Tarmoola trondhjemite intrusion. Gold-bearing veins post-date trondhjemite emplacement (ca. 2700 Ma), quartz diorite dikes (ca. 2667 Ma), and regional greenschist facies metamorphism. Textures and crosscutting relationships in gold-bearing veins indicate two stages of hydrothermal fluid infiltration associated with a single gold-related hydrothermal event: a volumetrically dominant, but gold-poor, stage I fluid and a gold-rich stage II fluid. Gold-bearing veins contain stage I milky quartz and pyrite that are overprinted by stage II quartz-ankerite-muscovite-chalcopyrite-sphalerite-galena-gold-tellurides ?? albite ?? chlorite ?? fuchsite ?? epidote ?? scheelite. Stage I hydrothermal alteration assemblages are different in trondhjemite and komatiite due to contrasting reactions between a common ore fluid and disparate wall-rock chemistry. Stage II fluid-wall rock interaction was minor compared to stage I and is indicated by the overprinting of stage I mineral assemblages by stage II microveins. Wall-rock alteration proximal to veins in trondhjemite is characterized by replacement of igneous plagioclase, amphibole, biotite, and metamorphic chlorite by hydrothermal quartz, muscovite, ankerite, calcite, pyrite, chalcopyrite, sphalerite, galena, tellurides, and gold, whereas in proximal alteration in komatiite, metamorphic chlorite and talc are replaced by ankerite, quartz, muscovite, albite, chlorite, fuchsite, pyrite, chalcopyrite, sphalerite, galena, tellurides, and gold. The stage II fluid was enriched in H2O, CO2, Si, Ca, K, Na, S, Au, Ag, Cu, Pb, W, Bi, As, Mo, Zn, and Te. Based on fluid inclusion

  12. Mars Express HRSC View of Western Olympus Mons: Evidence for Ice-bearing Deposit and High-Altitude Glaciation

    NASA Technical Reports Server (NTRS)

    Basilevsky, A. T.; Neukam, G.; Ivanov, B. A.; Werner, S. C.; vanGesselt, S.; Head, J. W.; Hauber, E.

    2005-01-01

    This study is based on the geological analysis of the HRSC images taken on the orbit 0143 (12 m/px in nadir channel). The study area includes the western segment of Olympus Mons and the adjacent lowland plains (Fig. 1). Part of the volcano above the scarp is rather flat and is called "summit plateau" below. What is often called the volcano scarp is a slope classified into three morphologic types: Type 1 (S1 in Fig.1) is the steepest and dominated by ravines in its upper part and by talus beneath; Type 2 (S2) is intermediate in steepness and dominated by downslope trending linear depressions, part of which have channel-like morphology; and Type 3 (S3), is the most gentle and covered by lava flows, continuing from the summit plateau down to the lowland plains.

  13. Soil mineral weathering in glacial deposits in the western Sierra Nevada and implication for U/Th geochronology

    NASA Astrophysics Data System (ADS)

    Aburto Guerrero, F. A.; Southard, R.

    2012-12-01

    During the Pleistocene vast alpine glaciers capped the Sierra Nevada range l and were a dominant force in shaping the post-glacial landscape. On the west side of the Lake Tahoe basin many moraine deposits stand out from the local morphology. Since their deposition these materials have been subject to physical and chemical weathering typical of this alpine environment. There is a general lack of information about soil weathering processes and rates for till deposits in alpine environments. We present the preliminary results of the mineralogical analysis of 13 granitic-derived soils located on Tioga (aprox. 19ka) and Tahoe age (aprox.118ka) moraine crests. A new light detection and ranging (LIDAR) dataset allowed geomorphic correlation of features using field reconnaissance and computer-based 3-D LIDAR data interpretation. A suite of mineralogical and elemental analyses, including XRD, DSC/TG and pXRF was performed, We also studied in-situ mineral transformations in selected durinodes by means of electron microprobe analysis and exploratory laser ablation coupled with mass spectrometry. Despite the large age difference in the deposits, Tahoe- and Tioga-age soils have very similar field morphology, making field discrimination extremely difficult. Mineralogical analysis reveals that soils on Tahoe-age moraines have clay mineralogy dominated by biotite and hydro-biotite, plus significant quantities of gibbsite and kaolinite. On the other hand, soils on Tioga-age moraines only have traces of gibbsite and kaolinite, and biotite is only slightly weathered. Elemental analysis suggests that Si and Al have been significantly mobilized exclusively in Tahoe-age soils. Increments in Al concentration coincide with relative gibbsite and kaolinite enrichment and plagioclase depletion. Si increment at deeper horizons seems to be associated with non-crystalline phases. Tioga-age durinodes are composed of till materials cemented by silica and contain coatings of micaceous materials

  14. Spatial and temporal distribution of Cu-Au-Mo ore deposits along the western Tethyan convergent margin: a link with the 3D subduction dynamics

    NASA Astrophysics Data System (ADS)

    Menant, A.; Bertrand, G.; Loiselet, C.; Guillou-Frottier, L.; Jolivet, L.

    2012-12-01

    Emplacement conditions of mineralized systems in subduction and post-subduction environments and the sources of metals such as Cu, Mo and Au have been considered in the past. However, despite their importance in exploration strategies at the continental scale, interrelationships between distribution of ore systems and subduction dynamics are still partly unclear. Along the western Tethyan convergent margin, where Tertiary subduction history is well constrained, porphyry, epithermal and skarn ore deposits show a variable evolution of their spatial distribution. Using different and complementary database on European and Middle East ore deposits, three metallogenic episodes have been highlighted: (1) a late Cretaceous - Paleocene phase characterized by a copper mineralization within the Balkan chain and in the Kaçkar mountains (eastern Turkey), (2) an Eocene phase with a few copper ore deposits in eastern Turkey and small Caucasia and (3) an Oligocene - Neogene phase with a more southern distribution along the margin and mainly constituted by epithermal Au systems in the west (Carpathians, Rhodope, Aegean and western Turkey) and by porphyry copper deposits in the east (Zagros). These changes are suspected to be controlled by complex and evolving subduction dynamics. Using paleogeographic tools, it turned out that, in the eastern Mediterranean area, the late Cretaceous - Paleocene and Oligocene - Neogene metallogenic episodes are coeval with a significant decrease of the Africa - Eurasia convergence rate, from about 1.5 to 0.4 cm/yr. Indeed, compressional tectonics in the volcanic arc domain, associated with a high convergent rate, promote the storage of large volumes of metal-rich magma and the development of an extensive MASH (melting, assimilation, storage and homogenization) zone. When this convergence rate decreases, a stress relaxation occurs in the overriding crust, inducing the ascent of a sufficient flux of this fertile magma and allowing the formation of

  15. Tectonic controls on deposition of Middle Jurassic strata in a retroarc foreland basin, Utah-Idaho trough, western interior, United States

    NASA Astrophysics Data System (ADS)

    Bjerrum, Christian J.; Dorsey, Rebecca J.

    1995-08-01

    An electronic supplement of this material may be obtained on a diskette or Anonymous FTP from KOSMOS.AGU.ORG. (LOGIN to AGU's FTP account using ANONYMOUS as the username and GUEST as the password. Go to the right directory by typing CD APEND. Type LS to see what files are available. Type GET and the name of the file to get it. Finally, type EXIT to leave the system.) (Paper 95TC01448, Tectonic controls on deposition of Middle Jurassic strata in a retroarc foreland basin, Utah-Idaho trough, western interior, United States, Christian J. Bjerrum and Rebecca J. Dorsey). Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N. W., Washington, DC 20009; $15.00. Payment must accompany order. A thick succession of Jurassic nonmarine and marine sedimentary rocks is exposed in a large area from northern Arizona to eastern Idaho and western Wyoming. These sediments accumulated in the Utah-Idaho trough, a deep elongate cratonal basin whose origin has recently been debated. Detailed stratigraphic analysis, subsidence analysis, and first-order flexural modeling of these deposits (this study) provide new insights into the timing and mechanisms of subsidence in the Utah-Idaho trough. Lower and Middle Jurassic strata are divided into six unconformity-bounded sequences. In contrast to the overall uniform thickness of Lower Jurassic sequences (1 and 2), Middle Jurassic strata (sequences 3 through 6) consist of distinctly westward thickening sedimentary packages in which basal shallow marine deposits onlap eastward onto bounding unconformities. Basal strata of sequences 3 through 6 pass upward into widespread progradational continental deposits that are truncated progressively toward the east (cratonward) by the next unconformity. Decompacted total subsidence curves show that the rate of subsidence in most sections increased sharply at the end of sequence 2 time (J-2 unconformity; ˜170 Ma). This is interpreted to record the onset of Middle Jurassic deposition

  16. Full depositional cycles and Ca/Mg ratio in marine upper Baku regiostage succession in the Western flank of the South Caspian depression

    NASA Astrophysics Data System (ADS)

    Amirov, Elnur

    2010-05-01

    The results of the field works on exposures of the Lower Pleistocene deposits located in the Western flank of the South Caspian depression (Shikhov outcrop) demonstrated the high-frequency cyclicity in sedimentation accompanied by rapid lateral and vertical depositional environmental change. It is possible to observe several full depositional sequences developed from low stand system tract to transgressive system tract and high stand system tract. Return to sedimentation under conditions of sea level low stand marks beginning of the next depositional cycle. The depositional setting during accumulation of this succession has changed within shore face-shelf environment. On the background of these cycles, the depositional series of higher order containing sediments formed during very small-scale sea level fall and rise occur. Below I give the lithofacial characteristics of one full depositional cycle and our interpretation of depositional environment during its sedimentation. Bedset I is subdivided into 10 interbeds with total thickness 2m70cm. Lithologically represented by alternation of sand, sandstone, sandy organogenic limestone, organogenic limestone and shelly sandstone. We consider these series as high stand system tract. Bedset II is the massive and homogeneous, thickness 1m10cm. Lithologically represented by organogenic limestones. We consider these series as low stand system tract. Bedset III is subdivided into 7 interbeds with total thickness 1m5cm. Lithologically represented by alternation of sand, sandstone, sandy organogenic limestone, organogenic limestone and shelly sandstone. We consider these series as high stand system tract. Bedset IV is the massive and homogeneous, thickness 2m. Lithologically represented by organogenic limestones. We consider these series as low stand system tract. Bedset V is subdivided into 13 interbeds with total thickness 4m30cm. Lithologically represented by alternation of sand, sandstone, sandy organogenic limestone and

  17. Biological N2-Fixation Increases with Peatland Age and Decreases with N Deposition in Bogs of Western Canada

    NASA Astrophysics Data System (ADS)

    Fillingim, H.; Popma, J. M.; Dynarski, K. A.; Wieder, R.; Vile, M. A.

    2013-12-01

    Most terrestrial ecosystems are thought be limited primarily by nitrogen, including boreal peatlands located in pristine regions. Bogs receive nutrients solely from atmospheric deposition. Because of the historically low rates of atmospheric nitrogen deposition in Alberta, Canada, the Sphagnum mosses that dominate bog ground cover in this region have formed relationships with diazotrophs in order to meet their nitrogen needs, making biological N2- fixation the dominant input of new nitrogen to these bogs. The process of N2-fixation is highly variable and is governed by a number of environmental factors. In Alberta, one factor is water availability, as these bogs occur in some of the driest climates in which peatlands are known to exist. More recent factors with the potential to greatly alter N2-fixation dynamics include increasing nitrogen deposition associated with the growing oil sands mining operations and wildfires increasing in frequency and severity with global climate change. To determine the potential importance of N2-fixation to the overall peatland nitrogen balance under current and future conditions, we incubated the moss Sphagnum fuscum, using the acetylene reduction assay calibrated with 15N2, from 3 bogs representing ages of 3, 13, and 30 years since fire. Each bog was fertilized 8 times throughout the growing season with 0, 10, and 20 kg N/ha/yr. N2-fixation rates were measured 5 times at each site throughout the summer of 2013 to account for variation due to season and weather. Mean rates of N2-fixation increased with bog age, with higher rates in the 30 year old bog (36.90 × 8.38) and subsequently lower rates in the 13 yr (25.08 × 5.63) and 3 yr (11.58 × 6.33) old bogs. As expected, we saw decreasing rates of N2-fixation in the 10 (16.96 × 5.39) and 20 kg N/ha/yr treatments (3.35 × 1.34), as compared to water-only controls (47.62 × 12.18). These results indicate that N2-fixation supplies abundant N to support net primary productivity for bogs

  18. Atmospheric deposition of current-use and historic-use pesticides in snow at National Parks in the Western United States

    USGS Publications Warehouse

    Hageman, K.J.; Simonich, S.L.; Campbell, D.H.; Wilson, G.R.; Landers, D.H.

    2006-01-01

    The United States (U.S.) National Park Service has initiated research on the atmospheric deposition and fate of semi-volatile organic compounds in its alpine, sub-Arctic, and Arctic ecosystems in the Western U.S. Results for the analysis of pesticides in seasonal snowpack samples collected in spring 2003 from seven national parks are presented herein. From a target analyte list of 47 pesticides and degradation products, the most frequently detected current-use pesticides were dacthal, chlorpyrifos, endosulfan, and ??- hexachlorocyclohexane, whereas the most frequently detected historic-use pesticides were dieldrin, ??-hexachlorocyclohexane, chlordane, and hexachlorobenzene. Correlation analysis with latitude, temperature, elevation, particulate matter, and two indicators of regional pesticide use reveal that regional current and historic agricultural practices are largely responsible for the distribution of pesticides in the national parks in this study. Pesticide deposition in the Alaskan parks is attributed to long-range transport because there are no significant regional pesticide sources. The percentage of total pesticide concentration due to regional transport (%RT) was calculated for the other parks. %RT was highest at parks with higher regional cropland intensity and for pesticides with lower vapor pressures and shorter half-lives in air. ?? 2006 American Chemical Society.

  19. Paleogeographical evolution of Vigla western Naxos (Cyclades, Greece), depositional environment and sea level changes in Upper Holocene.

    NASA Astrophysics Data System (ADS)

    Evelpidou, Niki; Pavlopoulos, Kosmas; Vassilopoulos, Andreas; Triantafyllou, Maria; Vouvalidis, Konstantinos; Syrides, George

    2010-05-01

    The study area of Vigla coastal zone is located at the W coast of Naxos, the largest island of Cycladic plateau. The study of sea-land interactions during Holocene in relation to the eustatic sea level oscillations as well as the geomorphologic observations and analyses on deposited sediments, aims to reveal the paleogeographic evolution of the landscape and its impact to the overall cultural development of the area. A geomorphological mapping of the coastal area along with the drilling of three boreholes has been accomplished. Moreover, a micro faunal analysis has been performed. Five samples of plant material, chart coal and shells were dated using AMS and Conventional radiocarbon techniques providing temporal control of the sediments. Sea level rise along with sea-land interactions to the landscape evolution and the transgression of sea in 5000 BP have been verified.

  20. Geological and geochemical characteristics in the paleo-weathering crust sedimentary type REE deposits, western Guizhou, China

    NASA Astrophysics Data System (ADS)

    Zhou, Lingjie; Zhang, Zhengwei; Li, Yujiao; You, Fuhua; Wu, Chengquan; Zheng, Chaofei

    2013-09-01

    A supergene REE deposit closely interrelated with the weathering of the Emeishan basalt formation was produced in the Xuanwei formation, the overlying stratum of the late Permian Emeishan basalt formation in West Guizhou, China. The host strata consist primarily of offwhite kaolinite clay rock and/or grayish black carbonaceous shale. Mineralogical analyses reveal that kaolinites are the major minerals in REE ores with small amounts of smectite, illite, boehmite, hornblende, pyrophyllite, calcite, dolomite and/or iron-bearing minerals, with a certain proportion of feldspar, quartz crystal debris and noncrystal debris. Geochemical analyses reveal high enrichment of trace elements like Cu, Nb, Ta, Zr and Hf. The host strata feature considerable lithological variability, close interrelation of the REE grade with the lithology and uneven spatial distribution of the REE ores, which are mostly found in Lufang, Maojiaping and Zhangsigou profiles of Weining County and can be as thick as 20 m. Of the five stratigraphic profiles, 48% have their whole-rock ∑REE higher than 1000 ppm. The REE in this framework consists primarily of ion adsorbed phases and REE-rich residual independent mineral phases. Comprehensive analyses suggest that the source may not only include the Emeishan basalt, but the intermediate acid volcanic rocks evolved from the Emeishan basalt in the later periods; the hydrothermal alteration subsequently imposed on the host strata might have boosted the mineralization of the rare earth. The preliminary genetic model should have been: the denudation product from the weathering of the parent rock was migrated to the sea-continental margin at the continent side carrying huge quantities of REE with it and was preserved by the quick marine transgression. The host strata consist primarily of kaolinite clay rock and/or carbonaceous shale, which are so far believed to be a sedimentary type REE deposit closely interrelated with weathering effect.

  1. Geology, petrography, geochemistry, and genesis of sulfide-rich pods in the Lac des Iles palladium deposits, western Ontario, Canada

    NASA Astrophysics Data System (ADS)

    Duran, Charley J.; Barnes, Sarah-Jane; Corkery, John T.

    2016-04-01

    The Lac des Iles Pd deposits are known for their Pd-rich sulfide-poor mineralization. However, previously undocumented sulfide-rich pods also occur within the intrusion that hosts the deposits. Given the complex magmatic and hydrothermal history of the mineralization at Lac des Iles, the sulfide-rich pods could have crystallized from magmatic sulfide liquids or precipitated from hydrothermal fluids. Sulfide-rich pods occur throughout the stratigraphy, in all rock types, and along comagmatic shear zones, and contain net-textured to massive sulfides. They can be divided into four main groups based on the variation in mineral assemblages: (1) pyrrhotite-pentlandite ± pyrite-chalcopyrite-magnetite-ilmenite; (2) chalcopyrite ± pyrrhotite-pentlandite-pyrite-magnetite-ilmenite; (3) pyrite ± pentlandite-chalcopyrite-pyrrhotite-magnetite-ilmenite; and (4) magnetite ± ilmenite-pyrrhotite-pentlandite-pyrite-chalcopyrite. Whole rock metal contents and S isotopic compositions do not change with the amount of pyrite present, except for slight enrichments in As and Bi. The presence of an essentially magmatic sulfide mineral assemblage (pyrrhotite-pentlandite ± chalcopyrite) with pentlandite exsolution flames in pyrrhotite in some pods suggests that the pods crystallized from magmatic sulfide liquids. The very low Cu contents of the pods suggests that they are mainly cumulates of monosulfide solid solution (MSS). We propose a model whereby sulfide liquids were concentrated into dilation zones prior to crystallizing cumulus MSS. Intermediate solid solution crystallized from the fractionated liquids at the edges of some pods leaving residual liquids enriched in Pt, Pd, Au, As, Bi, Sb, and Te. These residual liquids are no longer associated with the pods. During subsequent alteration, pyrite replaced MSS/pyrrhotite, but this did not affect the platinum-group element contents of the pods.

  2. Coal depositional models in some Tertiary and Cretaceous coal fields in the U.S. Western Interior

    USGS Publications Warehouse

    Flores, R.M.

    1979-01-01

    Detailed stratigraphic and sedimentological studies of the Tertiary Tongue River Member of the Fort Union Formation in the Powder River Basin, Wyoming, and the Cretaceous Blackhawk Formation and Star Point Sandstone in the Wasatch Plateau, Utah, indicate that the depositional environments of coal played a major role in controlling coal thickness, lateral continuity, potential minability, and type of floor and roof rocks. The potentially minable, thick coal beds of the Tongue River Member were primarily formed in long-lived floodbasin backswamps of upper alluvial plain environment. Avulsion of meandering fluvial channels contributed to the erratic lateral extent of coals in this environment. Laterally extensive coals formed in floodbasin backswamps of a lower alluvial plain environment; however, interruption by overbank and crevasse-splay sedimentation produced highly split and merging coal beds. Lacustrine sedimentation common to the lower alluvial plain, similar to the lake-covered lower alluvial valley of the Atchafalaya River Basin, is related to a high-constructive delta. In contrast to these alluvial coals are the deltaic coal deposits of the Blackhawk Formation. The formation consists of three coal populations: upper delta plain, lower delta plain, and 'back-barrier'. Coals of the lower delta plain are thick and laterally extensive, in contrast to those of the upper delta plain and 'back-barrier', which contain abundant, very thin and laterally discontinuous carbonaceous shale partings. The reworking of the delta-front sediments of the Star Point Sandstone suggests that the Blackhawk-Star Point delta was a high-destructive system. ?? 1979.

  3. Age and depositional setting of the Permian Black Dyke Formation: Implications for the paleogeography and structural evolution of western Nevada

    NASA Astrophysics Data System (ADS)

    Bleina, O.; Lapierre, H.; Schweickert, R. A.; Pêcher, A.; Monié, P.; Maluski, H.; Charvet, J.

    1999-09-01

    In western Nevada, the Black Dyke Formation includes volcanic rocks overlain conformably by volcaniclastic sediments. At the base, hornblende-phyric basalts with cognate hornblende-bearing gabbroic cumulates are interbedded with tuffs and pyroclastic breccia. Amphiboles give 40Ar/ 39Ar ages of 276 Ma. Clinopyroxene-phyric pillow basalts and plagioclase-phyric andesitic lava flows are present higher in the section. Facies changes between exposures reflect development near volcanic centers. According to our investigations, the Black Dyke Formation is involved in east-west-trending folds overturned toward the south, and overlain unconformably by the Mesozoic Dunlap Formation, which unconformably overlies the Mississippian-Permian Mina Formation. Interpreted until now as tectonic slices within the Luning allochthon, we suggest that the Black Dyke Formation is part of the Sonoma allochthon associated with the Mina Formation. The Sonoma records closure of the Havallah basin (Golconda allochthon), and collision of an arctrench system with the North American margin. The Black Dyke Formation exhibits similarities with the Permian arc sequence of the northern Sierra Nevada. Both sequences are characterized by amphibole-bearing breccias, clinopyroxene-phyric pillow-basalts, plagioclase-phyric andesites and overlying volcaniclastic sediments. These sequences developed in the same geodynamic environment (an islandarc).

  4. Allochthonous deep-water basin deposits of the western US: Implications for Paleozoic paleogeography and plate margin tectonics

    SciTech Connect

    Miller, E.L. . Geology Dept.)

    1993-04-01

    The stratigraphy and sedimentology of the lower Paleozoic Roberts Mts. and upper Paleozoic Golconda allochthons can be used to reconstruct their general paleogeographic setting in the Paleozoic. Basalt pillow lavas and radiolarian chert, were once considered straightforward evidence that the allochthons represented imbricated ocean crust formed at sites far removed from continental influences. Better stratigraphic definition, provenance studies and geochemistry of lavas now indicate that clastic components were derived from the continental shelf or interior and basalts in the Roberts Mountains allochthon were erupted in an intraplate setting through thinned continental crust (Madrid, 1987). Both in the earliest Mississippian and in the Late Permian, the Antler Basin (Roberts Mts.) and the Havallah Basin (Golconda) received proximal detritus from island arc sources to the west, immediately prior to closure of the basins by thrust-faulting. These data suggest that both systems of basins formed as marginal basins by rifting on the continental shelf (Antler Basin) and along the continental margin (Havallah Basin) and were flanked to the west by active island arcs at least during part of their history. As such, their stratigraphy provides a great deal of insight regarding tectonism along the western plate margin of North America during the Paleozoic.

  5. Metasedimentary rocks of the Angara-Kan granulite-gneiss block (Yenisey Ridge, south-western margin of the Siberian Craton): Provenance characteristics, deposition and age

    NASA Astrophysics Data System (ADS)

    Urmantseva, L. N.; Turkina, O. M.; Larionov, A. N.

    2012-04-01

    The Angara-Kan granulite-gneiss block (Yenisey Ridge) is one of the main basements uplift within the south-western margin of the Siberian Craton. The major part of the Angara-Kan block is composed of Early Precambrian high-grade metamorphic rocks. Metasedimentary association of the Kan granulitic complex is composed of garnet-bearing, garnet-orthopyroxene and orthopyroxene-bearing gneisses, garnet- and orthopyroxene-bearing gneisses with cordierite and sillimanite. Studied paragneisses were formed at the expense of granulite metamorphism of terrigenous rocks, ranging from graywacke to pelitic rock or mudstone. To estimate the time of sedimentation and metamorphism of the terrigenous deposits, the U-Pb zircon dating has been performed using the SHRIMP II ion microprobe. Detrital zircon cores from the biotite-orthopyroxene and high-alumina gneisses yield ages of 2.6-1.94 and 2.4-1.94 Ga, respectively. Together with the age of the magmatic zircons formed during high-grade metamorphism and partial melting (˜1.89 Ga) and metamorphic rims (˜1.87 Ga) it defines the time of sedimentation between 2.0-1.94 and 1.89-1.87 Ga. Detrital zircon ages indicate both Archean and Paleoproterozioc rocks in provenance source, that agrees with the Nd model ages of metasediments ranging in interval 2.4-2.8 Ga. Potential source of the Archean detrital zircons was the exposed basement of the southwestern Siberian Craton, whereas the Paleoproterozoic juvenile crustal source seems to be buried basement of the Tungus province of the Siberian Craton. Deposition of the Kan terrigeneous rocks was coeval with sedimentation in the southeastern part of the Sharyzhalgay uplift, where ages of detrital zircon cores and metamorphic rims from paragneisses bracket sediment deposition between 1.95 and 1.85 Ga.

  6. Geology, geochemistry and mineralogy of the lignite-hosted Ambassador palaeochannel uranium and multi-element deposit, Gunbarrel Basin, Western Australia

    NASA Astrophysics Data System (ADS)

    Douglas, Grant B.; Butt, Charles R. M.; Gray, David J.

    2011-10-01

    The Ambassador U and multi-element deposit occurs on the SW margin of the Gunbarrel Basin, Western Australia. Low-grade, flat-lying U mineralization averaging about 2 m thick at 0.03% U occurs in lignites at the redox front at the base of the weathering profile within a laterally extensive palaeochannel network. Uranium is principally associated with organic matter within the lignitic matrix, although rare discrete U minerals, such as coffinite and uraninite, are also present. The lignite is also enriched in a suite of other elements, principally base metals and sulphur, with concentrations of 0.3 ≥ 1% Cu, Pb, Ni, Co, Zn and total rare earth elements (REE) in some samples. Other element enrichments include: Cr, Cs, Sc, Se, Ta, Ti, Th, V and Zr as detrital heavy minerals of Zr, Ti and REE (oxides and silicates) or authigenic minerals of Cu, Bi, Pb, Zn, Ni, Se, Hg, Ti, Cr, Tl, V, U and REE (sulphides, vanadates, selenides, oxides, chlorides and native metals) and diffuse lignite impregnations. The Ambassador deposit probably formed from the convergence of redox-active weathering processes to unique source/host rocks, constrained within the palaeochannel. A proximal source of U and trace elements of lamproite/carbonatite origin is probable, as constrained by U-Pb isotope and U-Th disequilibria studies. Uranium and other metals were precipitated syngenetically with organic matter as it was deposited during a humid phase in the Late Eocene. Remobilization subsequently concentrated the metals in the upper 2 m of the lignite. This may have occurred during one or more periods of weathering and associated diagenesis, with the latest episode in the last 300,000 years.

  7. Dips, ramps, and rolls- Evidence for paleotopographic and syn-depositional fault control on the Western Kentucky No. 4 coal bed, tradewater formation (Bolsovian) Illinois Basin

    USGS Publications Warehouse

    Greb, S.F.; Eble, C.F.; Williams, D.A.; Nelson, W.J.

    2001-01-01

    The Western Kentucky No. 4 coal is a high-volatile B to high-volatile C bituminous coal that has been heavily mined along the southern margin of the Western Kentucky Coal Field. The seam has a reputation for rolling floor elevation. Elongate trends of floor depressions are referred to as "dips" and "rolls" by miners. Some are relatively narrow and straight to slightly curvilinear in plan view, with generally symmetric to slightly asymmetric cross-sections. Others are broader and asymmetric in section, with sharp dips on one limb and gradual, ramp-like dips on the other. Some limbs change laterally from gradual dip, to sharp dip, to offset of the coal. Lateral changes in the rate of floor elevation dip are often associated with changes in coal thickness, and in underground mines, changes in floor elevation are sometimes associated with roof falls and haulage problems. In order to test if coal thickness changes within floor depressions were associated with changes in palynology, petrography and coal quality, the coal was sampled at a surface mine across a broad. ramp-like depression that showed down-dip coal thickening. Increment samples of coal from a thick (150 cm), down-ramp and thinner (127 cm), up-ramp position at one surface mine correlate well between sample sites (a distance of 60 m) except for a single increment. The anomalous increment (31 cm) in the lower-middle part of the thick coal bed contained 20% more Lycospora orbicula spores. The rolling floor elevations noted in the study mines are inferred to have been formed as a result of pre-peat paleotopographic depressions, syn-depositional faulting, fault-controlled pre-peat paleotopography, and from compaction beneath post-depositional channels and slumps. Although the association of thick coal with linear trends and inferred faults has been used in other basins to infer syn-depositional faulting, changes in palynology within increment samples of the seam along a structural ramp in this study provide

  8. Depositional cycles and Fe/Mn ratio in Upper Absheron substage succession in the western flank of the South Khazarian/Caspian depression of the Azerbaijan Republic

    NASA Astrophysics Data System (ADS)

    Amirov, Elnur

    2016-04-01

    The Caspian Sea, the largest land locked basin in the world, isolated from ParaTethys at the end of Messinian. Since that time sedimentation there took place under conditions of isolated basin temporarily connected with Black Sea in Upper Pliocene (Akchagyl). For the first time very detailed study (centimeter scale) of outcrop was carried out for stratigraphy and paleoecology of the Upper absheron substage deposits cropped out in the Western flank of the South Caspian depression (Shikhovo exposure) of the Azerbaijan Republic. The data obtained demonstrated the high-frequency cyclicity in sedimentation accompanied by rapid lateral and vertical depositional environment change. Most of these system tracts have not yet been studied in detail. The depositional setting during accumulation of this succession has changed within shore face-shelf environment. On the background of these cycles, the depositional series of a higher order containing sediments deposited during very small-scale sea level fall and rise occur. Some information contained in this document is the new data, due to more recent observations and interpretations. The results of the field works on exposures of the Eopleistocene deposits exposed in the Western flank of the South Caspian depression (Shikhovo outcrop) demonstrated the high-frequency cyclicity in sedimentation. It is possible to observe several full depositional sequences developed from transgressive system tract to low stand system tract, to high stand system tract and return to sedimentation under conditions of sea level rise. The studied successions are characterized by steep foresets, about 12°, which is evidence of steep slope existed during the sediment accumulation. On the background of above mentioned cycles, the depositional series of a higher order containing sediments formed during very small-scale sea level fall and rise occur. Below we give the lithofacial characteristics of one full depositional cycle and our interpretation of

  9. Water Availability for Shale Gas Development in Sichuan Basin, China.

    PubMed

    Yu, Mengjun; Weinthal, Erika; Patiño-Echeverri, Dalia; Deshusses, Marc A; Zou, Caineng; Ni, Yunyan; Vengosh, Avner

    2016-03-15

    Unconventional shale gas development holds promise for reducing the predominant consumption of coal and increasing the utilization of natural gas in China. While China possesses some of the most abundant technically recoverable shale gas resources in the world, water availability could still be a limiting factor for hydraulic fracturing operations, in addition to geological, infrastructural, and technological barriers. Here, we project the baseline water availability for the next 15 years in Sichuan Basin, one of the most promising shale gas basins in China. Our projection shows that continued water demand for the domestic sector in Sichuan Basin could result in high to extremely high water stress in certain areas. By simulating shale gas development and using information from current water use for hydraulic fracturing in Sichuan Basin (20,000-30,000 m(3) per well), we project that during the next decade water use for shale gas development could reach 20-30 million m(3)/year, when shale gas well development is projected to be most active. While this volume is negligible relative to the projected overall domestic water use of ∼36 billion m(3)/year, we posit that intensification of hydraulic fracturing and water use might compete with other water utilization in local water-stress areas in Sichuan Basin. PMID:26881457

  10. Land-sea correlation between Late Holocene coastal and infralittoral deposits in the SE Iberian Peninsula (Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Fernández-Salas, L. M.; Dabrio, C. J.; Goy, J. L.; Díaz del Río, V.; Zazo, C.; Lobo, F. J.; Sanz, J. L.; Lario, J.

    2009-03-01

    The well-exposed systems of prograding beach ridges on the Carchuna-Calahonda (Granada) and Campo de Dalías-Roquetas (Almería) coastal plains continue offshore as infralittoral prograding wedges (IPW). The Holocene IPW is a narrow morpho-sedimentary unit up to 2.5 km wide which develops seaward from the lower edge of the shoreface to 15-20 m depth, extending to a well-defined break of slope at water depths of 35-40 m. These IPWs have been recognized and studied using very high-resolution seismic profiles (TOPAS) and multibeam data (EM-3000D). In detail they are complex morpho-sedimentary units in which internal structures are closely linked to the pattern of progradation of the adjacent coastal plains. When longshore currents produce significant littoral drift, the IPWs are composed of several minor units arranged in offlap, which accrete parallel or oblique to the main shoreline. Therefore, it is possible to correlate progradational units in the coastal plain (H-units, sensu[Goy, J.L., Zazo, C., Dabrio, C.J., 2003. A beach-ridge progradation complex reflecting periodical sea-level and climate variability during the Holocene (Gulf of Almería, Western Mediterranean). Geomorphology 50, 251-268]) and subunits in the IPW, but special care is required depending on the local arrangement of morpho-sedimentary units. Besides, it is not realistic to draw conclusions regarding the age of the subunits inside a given IPW without adequate dating, as the number of subunits will greatly vary from place to place depending on local factors, magnitude of sea-level oscillations, and sediment supply.

  11. SHRIMP U-Pb geochronology of volcanic rocks, Belt Supergroup, western Montana: Evidence for rapid deposition of sedimentary strata

    USGS Publications Warehouse

    Evans, K.V.; Aleinikoff, J.N.; Obradovich, J.D.; Fanning, C.M.

    2000-01-01

    New sensitive high resolution ion microprobe (SHRIMP) U-Pb zircon analyses from two tuffs and a felsic flow in the middle and upper Belt Supergroup of northwestern Montana significantly refine the age of sedimentation for this very thick (15-20 km) Middle Proterozoic stratigraphic sequence. In ascending stratigraphic order, the results are (1) 1454 ?? 9 Ma for a tuff in the upper part of the Helena Formation at Logan Pass, Glacier National Park; (2) 1443 ?? 7 Ma for a regionally restricted porphyritic rhyolite to quartz latite flow of the Purcell Lava in the Yaak River region; and (3) 1401 ?? 6 Ma for a tuff in the very thin transition zone between the Bonner Quartzite and Libby Formation, west of the town of Libby. Combining these ages with those previously published by other workers for ca. 1470-Ma sills in the lower Belt in Montana and Canada indicates that all but the uppermost Belt strata (about 1700 m) were deposited over a period of about 70 million years, considerably reducing the time span from longstanding estimates ranging from 250 to 600 million years. Calculated sediment accumulation rates between dated samples indicates rapid, but not unreasonable, values for early Belt strata, with decreasing rates through time. These ages also suggest the inadequacy of previously published paleomagnetic data to resolve Belt Supergroup chronology at an appropriate level of accuracy.

  12. Phosphate and sulfate-phosphate mineralization in sillimanite-bearing rocks at the Kyakhta deposit, western Transbaikal region

    NASA Astrophysics Data System (ADS)

    Izbrodin, I. A.; Ripp, G. S.; Karmanov, N. S.

    2009-12-01

    The phosphate and sulfate-phosphate minerals in the sillimanite-bearing rocks of the Kyakhta deposit are considered. The mineral assemblages of the high-Al rocks were formed during prograde and retrograde stages of metamorphism. The first stage is characterized by the formation of sillimanite, corundum, muscovite, quartz, rutile, titanohematite, magnetite, feldspar, biotite, lazulite, and wagnerite. The muscovite composition showed that sillimanite paragenesis was formed at temperatures above 510-600°C. According to oxygen isotope thermometry, the minimum metamorphic temperature for quartz and titanohematite is 690°C. Andalusite, diaspore, quartz, pyrophyllite, muscovite, and a wide range of phosphates and sulfate-phosphates crystallized during the retrograde stage. The decrease in temperature and increase in the water content led to the following sequence of mineral formation: Mg-Fe-Al-Ca-REE-rich phosphates (lazulite, scorzalite, augelite, apatite, and monazite) → Ca-Sr sulfate-phosphates (woodhouseite and svanbergite) → sulfate (barite) → Sr-Ca-Ba aluminophosphates (goyazite, crandallite, and gorceixite). The chemical compositions of phosphates and sulfate-phosphates minerals and their formation conditions are discussed.

  13. Foraminiferal biostratigraphy of the Toarcian deposits (Lower Jurassic) from the Middle Atlas (Morocco). Comparison with western Tethyan areas

    NASA Astrophysics Data System (ADS)

    Bejjaji, Zohra; Chakiri, Saïd; Reolid, Matías; Boutakiout, Mohamed

    2010-04-01

    The Toarcian sediments of the Middle Atlas show hemipelagic facies deposited in platform to basinal environments. They are represented by: (a) marly thick sections that accumulated in troughs under restricted dysoxic conditions, and (b) condensed sections of marly limestones found on fairly high ridges. The micropaleontological study of benthic foraminifera allowed us to establish the biostratigraphic extension of the different registered species. From the stratigraphic distribution of the benthic foraminifera two renewal phases can be characterized: one at the base of the Polymorphum Zone, and the other inside the Bifrons Zone. Five biozones were thus established ( Lingulina gr. tenera and Marginulina gr. prima Biozone; Lenticulina obonensis mg Planularia Biozone; Lenticulina pennensis mg Marginulinopsis and Ichtyolaria hauffi Biozone; Nodosariapulchra and Lenticulina ferruginea mg Falsopalmula Biozone; Lenticulinadorbignyi Biozone). These stratigraphic sub-divisions based on the benthic foraminifera are a useful tool when ammonoids are scarce. The Toarcian benthic foraminifera of the Middle Atlas are similar to the foraminiferal associations from neighbouring regions in the Maghreb (Morocco and Algeria) and Southwestern Europe (Spain, France and Portugal).

  14. Slip rate estimation along the western segment of the Main Marmara Fault over the last 405-490 ka by correlating mass transport deposits

    NASA Astrophysics Data System (ADS)

    Grall, C.; Henry, P.; Thomas, Y.; Westbrook, G. K.; ćaǧatay, M. N.; Marsset, B.; Saritas, H.; ćifçi, G.; Géli, L.

    2013-12-01

    3-D seismic data acquired in the Sea of Marmara on the Western High, along the northwestern branch of the North Anatolian Fault (also known as the Main Marmara Fault), shed new light on the evolution of the deformation over the last 500-600 ka. Sedimentary sequences in ponded basins are correlated with glacioeustatic cycles and transitions between marine and low sea/lake environments in the Sea of Marmara. In the 3 × 11 km2 of the 3-D seismic survey, deformation over the last 405-490 ka is localized along the main fault branch and north of it, where N130°-N140° trending normal faults and N40°-N50° folding accommodated strike-slip deformation associated with active argillokinesis. There is some evidence that deformation was more distributed further back in the past, at least over the depth range (<600 m below seafloor) of our survey. A N110° basin and buried ridge system were eventually cut by the presently active fault. The southern part of the basin was then uplifted, while the northern part was folded but continued to subside along the fault. A mass transport deposits complex dated between 405-490 ka shows a lateral displacement of 7.7 ± 0.3 km, corresponding to an estimated slip rate of 15.1-19.7 mm/a. We conclude that this strand of the Main Marmara Fault on the Western High has taken up most of the strike slip motion between the Anatolian and Eurasian plates over the last 405 ka at least.

  15. Effect of nine years of animal waste deposition on profile distribution of heavy metals in Abeokuta, south-western Nigeria and its implication for environmental quality.

    PubMed

    Azeez, J O; Adekunle, I O; Atiku, O O; Akande, K B; Jamiu-Azeez, S O

    2009-09-01

    Uncontrolled deposition of waste from animal farms is a common practice in south-western Nigeria, and the presence of heavy metals in soil constitutes environmental and health hazards by polluting the soil, ground water, adjoining streams and rivers. The study investigated the profile distribution of Mn, Pb, Cd, Zn, Fe, Cu, Ni and Cr in some tropical Alfisols in south-western Nigeria after nine years disposal of animal wastes. The amount of these metals in the soil horizons was high enough to cause health and phytotoxic risks. All the metals except Zn and Cr increased down the profile, while Mn, Pb, Cd, Fe, Cu and Ni accumulated at 80-120 cm depth. The increment of these metals at this depth over the top soil were 26%, 143%, 72%, 47%, 328% for Mn, Pb, Cd, Cu and Ni, respectively. It thus, shows their mobility and the possibility of polluting ground water. The Mn content at the poultry and cattle waste sites increased by 127% and 25%, respectively over the control, while that of cattle and swine dump site for Cd content were 9.82 and 15.63 mg kg(-1), respectively. Lead content also increased by 8.52 and 5.25 mg kg(-1), respectively. There was the accumulation of Zn and Cu at the swine dump site while the cattle dump site had the highest amounts of nickel and chromium. The least amount of Fe was recorded at the swine waste dump site. The reduction in organic matter with depths together with the reduced pH might have favored the mobility of the metals. The ranking of pollution among the sites was poultry>swine>cattle>sheep and could be due to the type of ration fed, the vaccination programmes, sanitation programmes and other management practices. PMID:19525105

  16. Decadal trend of black carbon and refractory carbonaceous aerosol in the western rim of the North Pacific Ocean: atmospheric concentration and the retrieved record of deposition flux

    NASA Astrophysics Data System (ADS)

    Kaneyasu, Naoki; Yamaguchi, Takashi; Noguchi, Izumi; Akiyama, Masayuki; Matsumoto, Kiyoshi

    2013-04-01

    The long-term trend of light absorbing carbonaceous aerosols (or black carbon: BC) or refractory carbonaceous aerosol (or elemental carbon: EC) concentration is reported at European background sites such as Mace Head, and that of aerosol absorption coefficient are monitored in many GAW sites. On the contrary, such long-term data are relatively scarce at around the western part of the North Pacific Ocean. Thus, to understand the long-term variation of in the area, BC in fine aerosol fraction has been measured at Chichi-jima Islands, Japan. Chichi-jima Island is located 1000 km south of the Japanese mainland, and 1800 km west of the coast line of the Asian continent. BC has been measured with an Aethalometer (Magee, AE-16 and AE-30) since December, 1998 with 1 hr time resolution. Mass flowmeter embedded inside the Aethalometer is calibrated with a rotational dry gas-meter once a year. Monthly averaged BC concentration shows an obvious seasonal variation, i.e. high concentration during late autumn-winter-spring period resulting from the transport from East Asia, with maximum daily concentration above 500 ng m-3. In summer, daily concentration was usually less than 20 ng m-3, due to the clean background airmass originating from the North Pacific Anticyclone. Decadal trend of the annual averaged BC concentration showed a increasing trend from 2000 to 2007 and started to decrease after 2008, which roughly coincides with the reported emission trend of SO2 in China (Lu et al., 2010). In addition, total (i.e., wet + dry) deposition record of refractory carbon at two sites in the northern Japan (Rishiri Island: a remote island site, and Sapporo City: an urban site) are retrieved. At these sites, the local government have been measuring the chemical components in precipitation water collected by deposition gauges. In the deposition gauge, a membrane filter made of cellulose-acetate is fixed at the bottom of the funnel to remove water-insoluble particles from the precipitated

  17. [Agro-ecosystem ammonia emission in Sichuan-Chongqing region].

    PubMed

    Li, Fu-chun; Han, Shen-hui; Yang, Jun; Zhang, Xu; Li, Ru-yan; Wei, Yuan-song; Fan, Mao-hong

    2009-10-15

    Ammonia (NH3) emission from agro-ecosystem in the Sichuan-Chongqing region during 1990-2004, was estimated by the regional nitrogen cycling model IAP-N. The county level agricultural activities data were used, and Sichuan-Chongqing region was divided into four sub-areas by the geographical characteristics , environment and local climatic conditions and administrative division. The results showed that average annual ammonia emissions (in nitrogen gauge) in 1990-1994, 1995-1999, 2000-2004 were 626.7, 670.5 and 698.8 Gg x a(-1) respectively. The ammonia emission appeared increasing trend, whereas, the contribution of various ammonia sources presented little change. For instance, in 2000-2004, the contributions of NH3 emission from fertilized cropland, manure management system and field residues burning to the total ammonia emission of agro-ecosystem in the Sichuan-Chongqing region were 53%, 46% and 1%, equals to 374.9, 318.2 and 5.6 Gg x a(-1) respectively. But the contributions were variable in different regions. Ammonia emission was primarily induced by fertilized cropland in Chengdu plain and Chongqing hilly area, whereas, in northwest sub-region of Sichuan province was manure management system. The geographical distribution of ammonia emission from agro-ecosystem in the Sichuan-Chongqing region was generally "east high and west low". Ammonia emissions in sub-regions of Chongqing hilly area, Chengdu plain, southwest and northwest sub-regions were 165.6, 408.8, 85.9 and 38.8 Gg x a(-1), respectively, during 2000-2004. At the same time, ammonia density were 20 and 28 kg x (hm2 x a)(-1) in sub-regions of the Chongqing hilly area and the Chengdu plain, whereas, 9.1 and 1.6 kg x (hm2 x a)(-1) in southwest and northwest sub-regions, respectively. The results will provide a scientific basis for making fertilizer effectively applied and mitigate NH3 and GHG emissions from agro-ecosystem of Sichuan-Chongqing region. PMID:19968093

  18. Probabilistic Analysis of Earthquake-Led Water Contamination: A Case of Sichuan, China

    NASA Astrophysics Data System (ADS)

    Yang, Yan; Li, Lin; Benjamin Zhan, F.; Zhuang, Yanhua

    2015-12-01

    The objective of this paper is to evaluate seismic-led point source and non-point source water pollution, under the seismic hazard of 10 % probability of exceedance in 50 years, and with the minimum value of the water quality standard in Sichuan, China. The soil conservation service curve number method of calculating the runoff depth in the single rainfall event combined with the seismic damage index were applied to estimate the potential degree of non-point source water pollution. To estimate the potential impact of point source water pollution, a comprehensive water pollution evaluation framework is constructed using a combination of Water Quality Index and Seismic Damage Index methods. The four key findings of this paper are: (1) The water catchment that has the highest factory concentration does not have the highest risk of non-point source water contamination induced by the outbreak of potential earthquake. (2) The water catchment that has the highest numbers of cumulative water pollutants types are typically located in the south western parts of Sichuan where the main river basins in the regions flow through. (3) The most common pollutants in sample factories studied is COD and NH3-N which are found in all catchments. The least common pollutant is pathogen—found present in W1 catchment which has the best rating in the water quality index. (4) Using water quality index as a standardization parameter, parallel comparisons is made among the 16 water catchments. Only catchment W1 reaches level II water quality status which has the rating of moderately polluted in events of earthquake induced water contamination. All other areas suffer from severe water contamination with multiple pollution sources. The results from the data model are significant to urban planning commissions and businesses to strategically choose their factory locations in order to minimize potential hazardous impact during the outbreak of earthquake.

  19. Probabilistic Analysis of Earthquake-Led Water Contamination: A Case of Sichuan, China

    NASA Astrophysics Data System (ADS)

    Yang, Yan; Li, Lin; Benjamin Zhan, F.; Zhuang, Yanhua

    2016-06-01

    The objective of this paper is to evaluate seismic-led point source and non-point source water pollution, under the seismic hazard of 10 % probability of exceedance in 50 years, and with the minimum value of the water quality standard in Sichuan, China. The soil conservation service curve number method of calculating the runoff depth in the single rainfall event combined with the seismic damage index were applied to estimate the potential degree of non-point source water pollution. To estimate the potential impact of point source water pollution, a comprehensive water pollution evaluation framework is constructed using a combination of Water Quality Index and Seismic Damage Index methods. The four key findings of this paper are: (1) The water catchment that has the highest factory concentration does not have the highest risk of non-point source water contamination induced by the outbreak of potential earthquake. (2) The water catchment that has the highest numbers of cumulative water pollutants types are typically located in the south western parts of Sichuan where the main river basins in the regions flow through. (3) The most common pollutants in sample factories studied is COD and NH3-N which are found in all catchments. The least common pollutant is pathogen—found present in W1 catchment which has the best rating in the water quality index. (4) Using water quality index as a standardization parameter, parallel comparisons is made among the 16 water catchments. Only catchment W1 reaches level II water quality status which has the rating of moderately polluted in events of earthquake induced water contamination. All other areas suffer from severe water contamination with multiple pollution sources. The results from the data model are significant to urban planning commissions and businesses to strategically choose their factory locations in order to minimize potential hazardous impact during the outbreak of earthquake.

  20. Active tectonic characteristics of river terraces along the Tianquan River, Sichuan, China

    NASA Astrophysics Data System (ADS)

    Cai, Y. M.; Shyu, J. B. H.; Chang, C. P.

    2015-12-01

    The Longmenshan fold-and-thrust belt at the western edge of the Sichuan Basin has long been identified as an active tectonic belt. This has been clearly illustrated by the disastrous Wenchuan and Lushan earthquakes in the recent decade. The two earthquakes, however, have distinctive characters. In the north, the Wenchuan event occurred on major fault zones identified previously. But in the south, the Lushan event was not accompanied by surface ruptures, and the seismogenic structure is still under debate. In order to further understand the neotectonic characteristics of the Lushan earthquake region, we analyzed fluvial terraces, in the hope that such geomorphic features would provide information of active structures of the area. Along the Tianquan River, river terraces are particularly well developed near two cities, Tianquan and Shiyang. Since the terraces appear to be very wide and limited in these two basin-like areas, we suspected that they formed as filled-up lakes. However, after detailed field investigations, we found that underneath these terraces, early Tertiary bedrocks crop out below river sediments that are only several meters thick. This indicates that the Tianquan River has incised into bedrocks. The slope of the terrace surfaces is similar to that of the present-day riverbed, and the river sediments in the terrace outcrops have similar grain size distribution as current riverbed sediments. Therefore, we suggest that the terraces along the Tianquan River are not related to dammed lake, but were produced by tectonic uplift. Combining the age of terrace sediments dated by optically stimulated luminescence (OSL) and detailed topography of the terrace surfaces, we aim to establish a model for the formation mechanism of these two terrace groups. We hope the results of this study would provide more information of neotectonic characteristics of the southwestern Sichuan Basin, as well as future earthquake hazards in this densely populated region.

  1. Western Samoa.

    PubMed

    1985-12-01

    agricultural, and the village communities maintain an economy based on farming and fishing. Stagnating or declining agricultural production has resulted in an increasing dependence on imports. The islands have few resources and no deposits of commercially valuable minerals. Western Samoa suffers from a persistent current accounts deficit. The government's primary goal is to improve agricultural production. Western Samoa has particularly close relations with its Pacific island neighbors and New Zealand. The US has taken a special interest in Western Samoa's economic development. PMID:12178131

  2. Dynamic responses of the benthic bacterial community at the Western English Channel observatory site L4 are driven by deposition of fresh phytodetritus

    NASA Astrophysics Data System (ADS)

    Tait, Karen; Airs, Ruth L.; Widdicombe, Claire E.; Tarran, Glen A.; Jones, Mark R.; Widdicombe, Stephen

    2015-09-01

    The impact of the seasonal deposition of phytoplankton and phytodetritus on surface sediment bacterial abundance and community composition was investigated at the Western English Channel site L4. Sediment and water samples were collected from January to September in 2012, increasing in frequency during periods of high water column phytoplankton abundance. Compared to the past two decades, the spring bloom in 2012 was both unusually long in duration and contained higher than average biomass. Within spring months, the phytoplankton bloom was well mixed through the water column and showed accumulations near the sea bed, as evidenced by flow cytometry measurements of nanoeukaryotes, water column chlorophyll a and the appearance of pelagic phytoplankton at the sediment. Measurements of chlorophyll and chlorophyll degradation products indicated phytoplankton material was heavily degraded after it reached the sediment surface: the nature of the chlorophyll degradation products (predominantly pheophorbide, pyropheophorbide and hydroxychlorophyllone) was indicative of grazing activity. The abundance of bacterial 16S rRNA genes g-1 sediment (used as a proxy for bacterial biomass) increased markedly with the onset of the phytoplankton bloom, and correlated with measurements of chlorophyll at the surface sediment. Together, this suggests that bacteria may have responded to nutrients released via grazing activity. In depth sequencing of the 16S rRNA genes indicated that the composition of the bacterial community shifted rapidly through-out the prolonged spring bloom period. This was primarily due to an increase in the relative sequence abundance of Flavobacteria.

  3. Composition and origin of fluids associated with lode gold deposits in a Mesoarchean greenstone belt (Warrawoona Syncline, Pilbara Craton, Western Australia) using synchrotron radiation X-ray fluorescence

    NASA Astrophysics Data System (ADS)

    Thébaud, Nicolas; Philippot, Pascal; Rey, Patrice; Cauzid, Jean

    2006-10-01

    Microthermometry and Raman spectroscopy techniques are routinely use to constrain ore-fluids δ18O and molar proportions of anhydrous gas species (CO2, CH4, N2). However, these methods remain imprecise concerning the ore-fluids composition and source. Synchrotron radiation X-ray fluorescence allows access to major and trace element concentrations (Cl, Br and K, Ca, Fe, Cu, Zn, As, Rb, Sr) of single fluid inclusion. In this paper, we present the results of the combination of these routine and newly developed techniques in order to document the fluids composition and source associated with a Mesoarchaean lode gold deposit (Warrawoona Syncline, Western Australia). Fluid inclusion analyses show that quartz veins preserved records of three fluid inclusion populations. Early fluids inclusions, related to quartz veins precipitation, are characterized by a moderate to high Br/Cl ratio relative to modern seawater, CO2 ± CH4 ± N2, low to moderate salinities and significant base metal (Fe, Cu, Zn) and metalloid (As) concentrations. Late fluid inclusions trapped in secondary aqueous fluid inclusions are divided into two populations with distinct compositions. The first population consists of moderately saline aqueous brines, with a Br/Cl ratio close to modern seawater and a low concentration of base metals and metalloids. The second population is a fluid of low to moderate salinity, with a low Br/Cl ratio relative to modern seawater and significant enrichment in Fe, Zn, Sr and Rb. These three fluid inclusion populations point to three contrasting sources: (1) a carbonic fluid of mixed metamorphic and magmatic origin associated with the gold-bearing quartz precipitation; (2) a secondary aqueous fluid with seawater affinity; and (3) a surface-derived secondary aqueous fluid modified through interaction with felsic lithologies, before being flushed into the syncline. Primary carbonic fluids present similar characteristics than those ascribed to Mesoarchaean lode gold deposits

  4. Senecio changii (Asteraceae: Senecioneae), a New Species from Sichuan, China.

    PubMed

    Ren, Chen; Tong, Tian-Jing; Hong, Yu; Yang, Qin-Er

    2016-01-01

    Senecio changii (Asteraceae: Senecioneae), a new species from Muli, Sichuan, southwestern China, is described. It is distinguished in Chinese Senecio s.s. by having lyrate-pinnatisect to pinnatisect leaves and a single terminal large discoid capitulum which is somewhat nodding. Evidence from floral micromorphology, karyology and molecular phylogenetic analyses based on the nuclear ITS/ETS sequence data all support its membership within Senecio s.s. PMID:27050905

  5. Senecio changii (Asteraceae: Senecioneae), a New Species from Sichuan, China

    PubMed Central

    Ren, Chen; Tong, Tian-Jing; Hong, Yu; Yang, Qin-Er

    2016-01-01

    Senecio changii (Asteraceae: Senecioneae), a new species from Muli, Sichuan, southwestern China, is described. It is distinguished in Chinese Senecio s.s. by having lyrate-pinnatisect to pinnatisect leaves and a single terminal large discoid capitulum which is somewhat nodding. Evidence from floral micromorphology, karyology and molecular phylogenetic analyses based on the nuclear ITS/ETS sequence data all support its membership within Senecio s.s. PMID:27050905

  6. Timing and duration of supergene mineralization at the Xinrong manganese deposit, western Guangdong Province, South China: cryptomelane 40Ar/39Ar dating

    NASA Astrophysics Data System (ADS)

    Li, Jian-Wei; Vasconcelos, Paulo; Zhang, Wei; Deng, Xiao-Dong; Duzgoren-Aydin, Nurdan; Yan, Dai-Rong; Zhang, Jian-Qiang; Hu, Ming-An

    2007-04-01

    Supergene Mn-oxide deposits are widely distributed in Guangxi, Guangdong, Yunnan, and Hunan Provinces, South China, accounting for 18% of the total Mn reserves in the country. Direct dating of supergene Mn enrichment, however, is lacking. In this paper, we present high-resolution 40Ar/39Ar ages of Mn oxides from the Xinrong Mn deposit, western Guangdong, to place numerical constraints on the timing and duration of supergene Mn enrichment. A total of ten cryptomelane samples, spanning a vertical extent of 67 m, were dated using the 40Ar/39Ar laser incremental heating technique, with seven samples yielding well-defined plateau or pseudo-plateau ages ranging from 23.48 ± 0.91 to 2.06 ± 0.05 Ma (2 σ). One sample yields a staircase spectrum that does not reach a plateau; the spectrum, however, indicates the presence of two or more generations of Mn oxides in the sample, whose ages are best estimated at 22.34 ± 0.31 and 10.2 ± 0.86 Ma, respectively. The remaining two samples gave meaningless or uninterpretable results due to significant 39Ar recoil and contamination by old phases. The 40Ar/39Ar data thus reveal a protracted history of weathering and supergene Mn enrichment that started at least in the end of the Oligocene or beginning of Miocene and extending into the latest Pliocene. Staircase-apparent age spectra, resulting from banded or botryoidal samples, yield an average growth rate of Mn oxides at 0.6-0.7 × 10-3 mm kyr-1. The values indicate that a 1-mm grain of Mn oxides may host minerals precipitated during a time span of ca. 1.5 m.y., and accumulation of Mn oxides to form economic deposits under weathering environments may take millions of years. The distribution of weathering ages shows that the oldest Mn oxides occur on the top of the profile, whereas the youngest minerals are found at the bottom, suggesting downward propagation of weathering fronts. However, two samples located at the intermediate depths of the profile yield ages comparable with those

  7. Psychological distress among adolescents in Chengdu, Sichuan at 1 month after the 2008 Sichuan earthquake.

    PubMed

    Lau, Joseph T F; Yu, Xiaonan; Zhang, Jianxin; Mak, Winnie W S; Choi, Kai Chow; Lui, Wacy W S; Zhang, Jianxin; Chan, Emily Y Y

    2010-05-01

    A devastating earthquake occurred on May 12, 2008 in Sichuan, China. This study investigated the prevalence and factors in association with psychological problems among secondary school students living in Chengdu (90 km away from the disaster epicenter) in June 2008. In a cross-sectional survey, 3,324 secondary students self-administered a structured questionnaire in classroom setting. Validated scales were used in this study. Among all respondents, 22.3% reported post-traumatic stress disorder (PTSD); 22.6% were probable depression cases; 10.6% reported suicidal ideation; and 14.1% would like to receive psychological counseling. No gender differences were found. While social/emotional support from teachers or peers (OR from 0.40 to 0.78) and exposure to positive news reports (OR from 0.59 to 0.62) were found protective, prior experience of severe mental distress (OR from 1.60 to 2.68) and corporal punishment (OR from 1.31 to 1.58), worry about future aftershocks (OR from 1.64 to 3.11), absence from school when it was not closed (OR from 1.38 to 1.48), exposures to scary or sorrowful disaster media coverage (OR from 1.39 to 2.07), post-disaster visits to affected sites (OR from 1.51 to 1.59), separation from parents (OR = 1.61), etc., were risk factors predictive of some of the aforementioned psychological problems. Negative mental health impacts were prevalent among the respondents. Teachers, parents, and the mass media are all important in maintaining good mental health among adolescents that are indirectly affected by the severe earthquake. The results have important implications for earthquake preparedness and relief work in the future. PMID:20405226

  8. Multiphase origin of the Cu Co ore deposits in the western part of the Lufilian fold-and-thrust belt, Katanga (Democratic Republic of Congo)

    NASA Astrophysics Data System (ADS)

    Dewaele, S.; Muchez, Ph.; Vets, J.; Fernandez-Alonzo, M.; Tack, L.

    2006-12-01

    A multiphase origin of the Cu-Co ores in the western part of the Lufilian fold-and-thrust belt in Central Africa is proposed based on literature, satellite image interpretations and petrographic and fluid inclusion analyses on samples from the stratiform mineralization of Kamoto and Musonoi (DR Congo). The various mineral occurrences in the Katanga Copperbelt can be classified in distinct categories: stratiform, supergene enrichment and vein-type. The stratiform mineralization form the largest group and can be found mainly in Lower Roan (R-2) rocks, which can be identified as ridges on satellite imagery. Ore deposits outside the R-2 occur along lineaments and result often from supergene enrichment. The main phase of the stratiform mineralization in the Katanga Copperbelt occurred during diagenesis preceding the Lufilian orogeny. Petrographic observation identified various mineralizing phases, which played a role in the formation of these stratiform mineralization. Mineralization started during early diagenesis, but mainly occurred during further burial. After the formation of early diagenetic pyrite, the circulation of diagenetic Cu-Co-rich fluids resulted in the formation of the main mineralization. Preliminary microthermometric investigation of primary inclusions in authigenic quartz, associated with the main stage of stratiform mineralization, indicates that an H 2O-NaCl fluid with a minimum temperature between 80 and 195 °C and a salinity between 8.4 and 18.4 eq. wt% NaCl circulated during the main phase of mineralization. Numerous faults and fractures formed during the Lufilian orogeny cut the stratiform mineralization. They are, however, at Kamoto and Musonoi only associated with minor sulphides. Supergene alteration along faults and fractures resulted in an enrichment of the mineralization, with the formation of secondary Cu-oxides, -carbonates and -silicates. The importance of the interaction of various processes for the formation of economic Cu-Co ore

  9. Hydrothermal remobilisation around a deformed and remobilised komatiite-hosted Ni-Cu-(PGE) deposit, Sarah's Find, Agnew Wiluna greenstone belt, Yilgarn Craton, Western Australia

    NASA Astrophysics Data System (ADS)

    Le Vaillant, Margaux; Saleem, Ahmad; Barnes, Stephen J.; Fiorentini, Marco L.; Miller, John; Beresford, Steve; Perring, Caroline

    2016-03-01

    The Sarah's Find nickel deposit, located 4.5 km north of the Mount Keith nickel mine, Western Australia, was chosen as a case study to investigate the nature and three-dimensional geometry of a geochemical halo created by the hydrothermal remobilisation of base metals and platinum group elements into the country rock surrounding a small massive Ni sulphide orebody. Portable and laboratory-based XRF analyses were carried out on samples from a shear zone localised along the basal komatiite-dacite contact that hosts the orebody. A geochemical halo was identified that extends along the shear zone up to 1780 m away from the massive sulphides, parallel to a prominent stretching lineation. Elevated Ni and Pd are associated with high As, Co, Cu and S. Palladium and Pt concentrations increase with proximity to massive sulphides (from 6 to 1190 ppb Pd). These anomalous concentrations reflect the presence of sulfarsenides and sulphides, either physically remobilised and forming veinlets close to the massive sulphides, or hydrothermally transported and redeposited within the foliation. In situ laser ablation ICP-MS indicates that Pd and Pt are hosted within these nickel sulfarsenides. This Ni-Co-As-Pd geochemical halo, observed around the Sarah's Find ore body, is interpreted as forming syn deformation, by the circulation of As-rich hydrothermal fluids dissolving base metals, Pd and Pt from the orebody and redepositing them along the sheared footwall contact. Similar Ni-Co-Pd-Pt-As geochemical haloes could potentially exist around any magmatic nickel sulphide mineral system that has undergone a phase of arsenic metasomatism and may be a generally applicable proximity indicator for nickel sulphides in hydrothermally altered terranes.

  10. Three dimensional surface displacement of the Sichuan earthquake (Mw 7.9, China) from Synthetic Aperture Radar.

    NASA Astrophysics Data System (ADS)

    de Michele, Marcello; Raucoules, Daniel; de Sigoyer, Julia; Pubellier, Manuel; Lasserre, Cecile; Pathier, Erwan; Klinger, Yann; van der Woerd, Jerome; Chamot-Rooke, Nicolas

    2010-05-01

    The Sichuan earthquake, Mw 7.9, struck the Longmen Shan range front, in the western Sichuan province, China, on 12 May 2008. It severely affected an area where little historical seismicity and little or no significant active shortening were reported before the earthquake (e.g. Gu et al., 1989; Chen et al., 1994; Gan et al., 2007). The Longmen Shan thrust system bounds the eastern margin of the Tibetan plateau and is considered as a transpressive zone since Triassic time that was reactivated during the India-Asia collision (e.g., Tapponnier and Molnar, 1977, Chen and Wilson 1996; Arne et al., 1997, Godard et al., 2009). However, contrasting geological evidences of sparse thrusting and marked dextral strike-slip faulting during the Quaternary along with high topography (Burchfiel et al., 1995; Densmore et al., 2007) have led to models of dynamically driven and sustained topography (Royden et al., 1997) limiting the role of earthquakes in relief building and leaving the mechanism of long term strain distribution in this area as an open question. Here we combine C and L band Synthetic Aperture Radar (SAR) offsets data from ascending and descending paths to retrieve the three dimensional surface displacement distribution all along the earthquake ruptures of the Sichuan earthquake. For the first time on this earthquake we present near field 3D co-seismic surface displacement, which is an important datum for constraining modelled fault geometry at depth. Our results complement other Interferometric Synthetic Aperture Radar (InSAR) and field analyses in indicating that crustal shortening is one of the main drivers for topography building in the Longmen Shan (Liu-Zeng, 2009; Shen et al., 2009; Hubbard and Shaw, 2009). Moreover, our results put into evidence a small but significant amount of displacement in the range front that we interpret as due to slip at depth on a blind structure. We verify this hypothesis by inverting the data against a simple elastic dislocation model