Chemistry and Sulfur Isotopes of the Chert-Clastic Sequence Surrounding the Kajika Massive Sulfide Ores at the Ashio Copper Mine, Ashio Terrane, Central Japan     

Kosei Komuro    Masanori Yoshida  Yoshimichi Kajiwara 《Resource Geology》2006,56(4):433-445

Abstract. Chemical and sulfur isotopic compositions were obtained for a series of rocks within the chert‐clastic sequence surrounding the Kajika massive sulfide ore horizon at Shibukawasawa in the Ashio copper‐mining district, Ashio Terrane, central Japan. The sequence is lithologically classified into three units: chert, siliceous shale with basic volcanics, and sandstone‐shale, in ascending stratigraphic order. The Kajika ore horizon corresponds to the lowermost part of the unit that contains siliceous shale with basic volcanics. The rocks around the Kajika ore horizon are enriched in P₂O₅ (max. 0.22 %), Ba (max. 2400 ppm), Cu (595 ppm), V (323 ppm), Pb (168 ppm), Zn (124 ppm), and Mo (24 ppm) in siliceous shale; and Ba (4220 ppm), Zr (974 ppm), Cr (718 ppm), Ni (492 ppm), V (362 ppm), Zn (232 ppm), Nb (231 ppm), and Co (71 ppm) in the basic volcanics. The siliceous shale is enriched in a number of redox‐sensitive elements such as Cu, V, Pb, Zn, and Mo, which are known to be enriched in black shale and anoxic and hydrothermal sediments. The δ³⁴S values of sulfides in the chert and sandstone‐shale lie in the range of 0±2 %, and those in the siliceous shale range from ‐5 to ‐14 %. The measured δ³⁴S values in the basic volcanics are ‐0.3, ‐2.7, and ‐31.5 %. These heavier δ³⁴S signatures (around 0 %) recorded throughout the sequence indicate that the rocks formed under anoxic bottom‐water conditions. Slightly lighter δ³⁴S values recorded in siliceous shale might reflect significant mixing of sulfides that formed by sulfate‐reducing bacteria in an overlying oxic environment. The long‐term duration of anoxic conditions indicated by the heavier δ³⁴S signature is considered to have played an important role in protecting the Kajika sulfide ores from oxidative decomposition and preserving the ores in sedimentary accumulations.  相似文献   

Sulfur Isotope Geochemistry of the Supergiant Xikuangshan Sb Deposit, Central Hunan, China: Constraints on Sources of Ore Constituents   总被引：2，自引：0，他引：2  

Dong-sheng Yang    Masaaki Shimizu  Hidehiko Shimazaki    Xian-hua Li  Qing-lin Xie 《Resource Geology》2006,56(4):385-396

Abstract. The supergiant Xikuangshan Sb deposit is located in the Middle to Upper Devonian limestone of central Hunan, China. Primary ores are composed of early-stage stibnite and calcite with rare pyrite, early main-stage stibnite and quartz, and late main-stage stibnite and calcite. New sulfur isotope data reveal the clustering of δ³⁴S values (+5 ∼ +8 %) for both early and late main-stage stibnite; a single early-stage stibnite exhibits δ³⁴S value (+7.5 %) identical to its main ore-stage counterparts and the coexisting calcite has almost unmodified carbon isotope composition (-4.4 %). The data suggest a probable common source of sulfur for stibnite that was deposited at different paragenetic stages. A much wider variation in δ³⁴S values for early main-stage stibnite (+3.5 to +16.3 %, av. +7.5 %) compared to that for late main-stage stibnite (+5.3 to +8.1 %, av. +6.2 %) can be interpreted to be due to local interaction of earlier ore fluid with Devonian host rocks. The previous studies show that the Precambrian basement contains elevated Sb concentrations, and two distinctive sulfur reservoirs with δ³⁴S_pyrite values at ca. +11 ∼ +24 % and -7.0 ∼-11 %. The homogenizing effect for sulfur hydrothermally leached from the two reservoirs might have provided ore constituents for the Xikuangshan fluids.  相似文献   

Acid rain in China-Input-output budgets of major ions in four forested catchments     

Thorjorn Larssen 《中国地球化学学报》2006,25(B08):49-49

Acid rain is one of China＇s major environmental problems and emissions of sulphur and nitrogen are still increasing. The acid rain situation in China is somewhat different from what is seen in Europe and North America. Sulfur deposition is very high, but there is also very high deposition of calcium and other base cations. The sources of atmospheric Ca are not well understood, although it is important for understanding long term impacts of acid deposition. The fate of S, N and Ca^2＋ in the catchment is crucial for the future development of the acidification situation of soils and waters in China. Very few studies presenting catchment input-output ion budgets in Chinese natural environments exist and there are several unknown factors regarding processes. Here, we present annual input-output budgets for three years （2001-2003） for major ions for four forested catchments in China receiving different loads of acid deposition. For the two sites receiving the highest SO4^2- inputs, the input-output budget for the upper 50 cm of soil is approximately balanced. For the most remote site the soil is a net sink for SO4^2-, suggesting that the pool of adsorbed SO4^2- in the soil is building up. This is in agreement with the fact that the site so far has received only moderate SO4^2- inputs. For the southemmost, the subtropical site there is a loss of SO4^2- in the soil, which at least partly may be related to high uptake from the dense and highly productive forest at the site. The Ca^2＋ budgets for the upper 50 cm of soil show large variations both within and between sites. For most locations there is production of Ca^2＋ in the soil that can be explained by weathering, and variation between years related to hydrology that can be explained by ion exchange. However, at some plots at the site receiving very high inputs of both SO4^2- and Ca^2＋, there is an unknown sink of Ca^2＋ in the soil at some plots.  相似文献   

Evolution of a Porphyry-Cu Mineralized Magma System at Santa Rita, New Mexico (USA)   总被引：1，自引：0，他引：1  

AUDETAT  A.; PETTKE  T. 《Journal of Petrology》2006,47(10):2021-2046

The magmatic processes leading to porphyry-Cu mineralizationat Santa Rita are reconstructed on the basis of petrographicstudies, thermobarometry, and laser-ablation inductively-coupled-plasmamass-spectrometry analyses of silicate melt and sulfide inclusionsfrom dikes ranging from basaltic andesite to rhyodacite. Combinedresults suggest that magma evolution at Santa Rita is similarto that of sulfur-rich volcanoes situated above subduction zones,being characterized by repeated injection of hot, mafic magmainto an anhydrite-bearing magma chamber of rhyodacitic composition.The most mafic end-member identified at Santa Rita is a shoshoniticbasaltic andesite that crystallized at 1000–1050°C,1–3 kbar and log f_O2 = NNO + 0·7 to NNO + 1·0,whereas the rhyodacite crystallized at 730–760°C andlog f_O2 = NNO + 1·3 to NNO + 1·9. Mixing betweenthe two magmas caused precipitation of 0·1–0·2wt % magmatic sulfides and an associated decrease in the Cucontent of the silicate melt from 300–500 ppm to lessthan 20 ppm. Quantitative modeling suggests that temporal storageof ore-metals in magmatic sulfides does not significantly enhancethe amount of copper ultimately available to ore-forming hydrothermalfluids. Magmatic sulfides are therefore not vital to the formationof porphyry-Cu deposits, unless a mechanism is required thatholds back ore-forming metals until late in the evolution ofthe volcanic–plutonic system. KEY WORDS: porphyry-Cu; sulfur; sulfides; magma mixing; LA-ICP-MS  相似文献   

Airborne measurements of particle and gas emissions from the December 1994–January 1995 eruption of Popocatépetl volcano (Mexico)     

Ignacio Galindo  Lev S. Ivlev  Arturo Gonzlez  Roberto Ayala 《Journal of Volcanology and Geothermal Research》1998,83(3-4)

Airborne and ground-based (correlation spectrometer, cascade impactor, and photoelectric counter together with intake filter probes) measurements are described for the volcanic emissions from Popocatépetl volcano (Mexico) from December 23, 1994 to January 28, 1995. Measurements of SO₂ restarted 48 h after the eruption onset of December 21, 1994. Maximum sulfur dioxide (4560 t d⁻¹) plus 3.8×10⁴ t d⁻¹ of particulate matter were ejected on December 24, 1994. The maximum rate of ejection occurred coincidentally with the maximum amplitude of harmonic tremor and the maximum number of seismic type B events. Sulfur dioxide emission rates ranged from 1790 to 2070 t d⁻¹ (December 23–24, 1994). Afterwards, sulfur dioxide emission rates clearly indicated a consistent decline. However, frequent gas and ash emission puffs exhibited SO₂ fluxes reaching values as high as 3060 t d⁻¹. The emission SO₂ baseline for the period of study (February 1994–January 1995) was about 1000 t d⁻¹. Ejection velocity of particulate matter was approximately 270 m s⁻¹ reaching a height of about 2.5 km over the summit. The immediate aerosol dispersion area was estimated at 6.0×10⁴ km² maximum. The microscopic structure of particles (aerosol and tephra) showed a fragile material, probably coming from weathered crustal layers. X-ray fluorescence and neutron-activation analysis from the impactor samples found the following elements: Si, Al, Ca, S, P, Cl, K, Ni, Fe, Ti, Sc, Cu, Zn, Mn, Sr, Cr, Co, Y, Br, Se, Ga, Rb, Hg and Pb. Morphological analysis shows that ash samples might be from pulverized basaltic rock indicating that the Popocatépetl eruption of December 21, 1994 was at low temperature. The microscopic structure of puff material showed substance aggregates consisted of fragile rock, water and adsorbed SO₂. These aggregates were observed within water droplets of approximately 1 mm and even larger. Sulfur transformations in the droplets occurred intensively. Volcanic ash contained 5–6% of sulfur during the first expulsion hours. Elemental relative concentrations with respect to Al show that both Si and S have relative concentrations >1, i.e., 13.73 and 2.17, respectively in agreement with the photoelectric counter and COSPEC measurements.  相似文献   

陆相低成熟烃源岩有机硫与热解成烃动力学关系初探   总被引：5，自引：0，他引：5  

沈忠民  周光甲 《沉积学报》1998,16(4):133-139

对陆相低成熟烃源岩（R_o≤ 0.5 %）有机硫与成烃动力学关系进行了研究。结果表明:①有机硫含量与镜质体反射率（R_o）之间呈负相关关系,即有机硫含量随成熟度提高而减少;②源岩的平均活化能（E）有随有机硫含量增大而减小的趋势;③有机硫含量与源岩活化能分布最小值（E_min）和经可溶有机质抽提后的活化能分布最小值（E_min）之间存在正相关关系;④活化能分布范围E_min～ESE_min（ESE_min＞E_min）内的可溶有机质生烃能力与有机硫含量具有一定的相关性;⑤综上结果推断东营凹陷南斜坡东段沙四段（Es₄）源岩中的有机硫在成烃过程中可能起到了一定的作用。  相似文献   

用加压氧化—氰化法从硫精矿中提金试验研究   总被引：4，自引：0，他引：4  

薛光 《黄金地质》1998,4(4):68-71

采用“高效浸金反应器”研究了加压氧化－氰化法提金新工艺。对山东某地硫精矿采用此工艺,选择条件为氰化钠用量１．５ｋｇ／ｔ、石灰用量７ｋｇ／ｔ、矿浆固液比１：１５、浸出时间３０ｍｉｎ,金浸出率可达６２％,与常规氰化法相比成本低,效率高。  相似文献   

内蒙古乌拉山金矿带硫同位素特征研究   总被引：2，自引：0，他引：2  

郎殿有  李伟 《内蒙古地质》1998,(1)

本文对乌拉山金矿带西段硫同位素组成特征进行了研究,同时参照前人对东段硫同位素研究成果,对比东、西两段硫同位素组成特点。同时计算了硫化物沉淀时同位素的平衡温度,探讨了硫的来源。认为硫主要来源于深源重熔岩浆热液。在乌拉山金矿形成过程中,亦有非岩浆物质——变质岩中轻硫成分的混入。  相似文献   

中低温开放含硫水热体系中水岩淋滤实验研究   总被引：7，自引：0，他引：7  

卢新卫  解庆林  马东升  刘英俊 《矿床地质》1998,17(2):185-191

针对湘中湘西矿区的地质实际在１００￣３００℃,２０ＭＰａ压力条件下,对中低温开放含硫水热体系地层岩石中Ｓｂ、Ａｓ、Ｈｇ的多元素进行了淋滤实验研究。实验结果表明,随温度的升高,Ｓｂ和Ｈｇ的淋滤率增大;低温富硫热液有利于Ｓｂ和Ａｓ的活化迁移。同时,水岩比值、岩性以及岩石中元素的存在形式也是控制元素活化能力的重要因素。  相似文献   

The Holocene development of Kushu Lake on Rebun Island in Hokkaido, Japan     

H. Sato  S. Kumano  Y. Maeda  T. Nakamura  I. Matsuda 《Journal of Paleolimnology》1998,20(1):57-69

Diatom assemblages and sulfur content in sediments were analyzed to clarify changes in the sedimentary environment of Kushu Lake, a coastal lake on Rebun Island in Hokkaido, Japan. Salinity variations were assessed by means of a diatom-based index of paleosalinity and the sedimentary sulfur content. This paper discusses the Holocene development of the lake, in relation to Holocene relative sea-level change. For paleoenvironmental interpretation of the lake development, the rationale of the threshold method (Anundsen et al., 1994) was applied.At ca. 8000 yr BP, a coastal embayment (paleo-Kushu Bay) resulted from marine ingression. The threshold elevation at the mouth of the paleo-Kushu Bay kept pace with the rising sea-level, resulting in its enclosure at the culmination of Holocene marine transgression (ca. 6500–5000 yr BP). From predicted relative sea-level at ca. 6000 yr BP for Rebun Island (Nakada et al., 1991), the threshold may have been at least above –3 to –5 m altitude. A freshwater lake environment with strongly anoxic bottom conditions may have occurred from ca. 5500 to 5100 yr BP. After an important episode of marine ingression, the lake was isolated completely from the open sea at ca. 4900 yr BP. The diatom record suggests that the maximum lacustrine extent occurred at ca. 4900–3100 yr BP. Thereafter, water depth decreased at the lake margins.In Kushu Lake, the threshold elevation, due to a build-up of a coastal barrier, prevents us from determining the amplitude of sea-level changes, even though the age of isolation contacts corresponds to periods of regression and climatic deterioration. In spite of isostatic subsidence, the effective protection provided by the well-developed barrier did not allow registration of any relative sea-level fluctuations since its isolation.  相似文献