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991.
Alireza Zarasvandi David Lentz Mohsen Rezaei Houshang Pourkaseb 《Chemie der Erde / Geochemistry》2013
The Nasirabad manganese occurrence is located to the south of the Neyriz in the Fars province. Structurally and lithologically, this occurrence lies in the southwest part of the Zagros Thrust Belt and was deposited as Mn-nodules and interconnected ore-bearing interlayer's with radiolarite cherts in the vicinity of the Neyriz ophiolites. The present work deals with the geology and geochemistry of the Nasirabad manganese occurrence with a discussion of its genesis. High Mn/Fe (average 18.85) and high Ba (average 28,830 ppm) with low Pb (2.0 ppm) and LREE > HREE, Lan/Ndn (average 4.5), Dyn/Ybn (average 1.2) and negative Eu anomaly suggest distal hydrothermal source. The Co/Zn (average 2.2), Ce/La ratio (average 0.67) and trace element discrimination diagrams indicate hydrothermal–hydrogenous processes. Y/Ho ratio (average 24.85) and strong positive correlation coefficient between major oxides and some high field strength elements (HFSE) like; TiO2 vs Fe2O3 (r = 0.98), Al2O3 vs Zr (r = 0.97), Al2O3 vs Fe2O3 (r = 0.98), Zr vs K2O (r = 0.98), Nb vs TiO2 (r = 0.92), Th vs Fe2O3 (r = 0.76), Th vs MgO (r = 0.86) reveal the presence of volcaniclastics and (or) terrigenous detritals of mafic composition being deposited into the depositional basin. It seems that intermittent interlayering of mafic detrital material derived from volcanic eruption of the Neyriz island arc directly affected the physicochemical conditions of hydrothermal ore precipitation in this basin and consequently the Nasirabad manganese ores represent hydrothermal–hydrogenous geochemical characteristics. The Nasirabad is an example of non-sulphidic, oxic Mn-mineralization. Similar trend between the enrichment and depletion of some bioessential elements (e.g., Mn, As, Ba, Sr, Co, Ce) might have been resulted from selective sequestering of metal ions by microbial processes and hence hydrogenous characteristics may also be the result of biogenetic processes. Moreover the high dilution of distal hydrothermal exhalations by sea water cannot be ruled out. 相似文献
992.
Hydrochemical characteristics and controlling factors for waters’ chemical composition in the Tarim Basin,Western China 总被引:1,自引:0,他引:1
This paper covers the chemical and isotopic composition of river water, groundwater from wells (15–25 m), saline spring water and stagnant surface water providing evidence for controlling factors of water composition and water evolution process in the Tarim Basin, Xinjiang, western China. Analytical data for major and minor ions of totaling 537 water samples were obtained from both years of teamwork and old reference materials. It is found that the ion background value ratio SO4/Cl for river water (2.75) of the Tarim Basin is two times higher than that of the Qaidam Basin (0.88) and 18 times higher than seawater (0.14); K/Cl of these two basins (0.06 and 0.07) are all two times higher than seawater (0.02). This reveals that material sources of Lop Nur are relatively richer in potassium and sulfate, while poorer in chloride. Gradual changes of stable isotopic compositions in waters clearly indicate the effect of evaporation on water evolution of the basin. Besides evaporation and weathering of surrounding rocks, wide distribution of chloride type water, which commonly exist in saline springs/brines and seldom exist in other waters, indicates that hydrothermal Ca–Cl brines discharged from deep within the earth join water evolution of the basin. 相似文献
993.
994.
岔河铁矿产于构造破碎带中,似层状产出,围岩和矿体中石英、方解石脉发育,矿床成因属浅海一滨海相沉积变质型褐铁矿床. 相似文献
995.
松诺铜多金属矿区地质背景类似于普朗铜矿,异常元素组合与普朗斑岩型铜矿相似,同时均属同一构造岩浆岩带,松诺是寻找“普朗式铜矿”最有利地段. 相似文献
996.
997.
湖北嘉鱼蛇屋山红土型金矿研究回顾与展望 总被引:1,自引:0,他引:1
蛇屋山红土型金矿是鄂东南地区规模最大的金矿,自该矿发现始,围绕该矿及类似矿床研究,已获得了大量的研究成果,但该矿床成因认识、成矿过程等方面仍存在许多争议。作者通过大量室内资料分析及野外进行实地调研,找出了该矿床研究中争议的焦点及各自依据,并介绍了与蛇屋山相关的国外同类矿床成因及勘查进展,蛇屋山金矿找矿研究工作部分进展,以期为该矿今后的科研和找矿工作提供新的思路,并认为该矿床远景有可能达到超大型矿床规模。 相似文献
998.
胶东金矿是全球最大的与花岗岩有关的大型金矿床。前人研究多数与板块构造碰撞或俯冲联系起来,提出“造山带型金矿”或“变质核杂岩”等观点。本文指出,胶东金矿形成于中国东部板块拼合后的大陆,属于陈国达曾厘定的中生代地洼区(陈国达,1956,1985;邓军等,1998;翟明国等,2004),受控于一种“岩浆核杂岩”的构造(吕古贤等,2016)。胶东“岩浆核杂岩隆起—拆离带蚀变岩金矿床”,在全球已知金矿床类型中是独特的(吕古贤等,1999,2013)。胶东“岩浆核杂岩”构造在中国中新生代复合大陆可能较普遍发育。 相似文献
999.
1000.
This study was aimed to test a new methodological approach to carry out measurements of gaseous elemental mercury (GEM) diffusively emitted from soils in hydrothermal-volcanic environments. This method was based on the use of a static closed-chamber (SCC) in combination with a Lumex® RA-915M analyzer that provides GEM measurements in a wide range of concentrations (from 2 to 50,000 ng m−3). Gas samples were collected at fixed time intervals from the SCC positioned on the ground (time-series samples). The Lumex® inlet port was equipped with a three-way Teflon valve allowing the free entrance of air through a carbon trap, in order to: (i) prevent disturbance to the Lumex® operative flow rate (10 L min−1) during the injection of the gas samples from the SCC and (ii) minimize the instability of the baseline signal induced by possible variations of GEM concentrations in air. In the lab, known amounts of GEM, pipetted from a vessel containing an Hg-saturated air in equilibrium with liquid mercury at 27 °C, were injected in the Lumex® via the modified inlet port to construct a calibration curve. The latter was used to calculate the amount of GEM in the SCC (KSCC) from the corresponding GEM concentrations measured by the Lumex® analyzer. The KSCC values of the time-series samples were proportionally increasing with the GEM fluxes (ϕGEM), thus ϕGEM values were computed according to the following equation: ϕGEM = (dKSCC/dt)/A, where A is the basal area of the SCC and dt is the time interval of the time-series sampling. Up to 214 ϕGEM measurements were carried out at Solfatara crater (Campi Flegrei, southern Italy), a hydrothermally altered tuff cone characterized by an anomalous diffuse soil emission of GEM-rich geogenic gases. The measured ϕGEM values varied up to 4 orders of magnitude, from 1,296, corresponding to the sensitivity of the method at the selected sampling time interval (1 min), to 1,957,500 ng m−2 day−1, and were consistent with those recently measured in this crater using a different method. In the field, 10 replicates were carried out in 5 selected sites, allowing to demonstrate that the proposed method has a high reproducibility (RDS < 4%). The ϕGEM and ϕCO2 values, the latter being measured in the same 214 sites by using the accumulation chamber method, showed a low correlation, although both gases were originated from the same deep source. This suggests that GEM and CO2 soil fluxes are differently affected by environmental parameters, such as soil humidity and temperature, which have a strong effect on the release of GEM from the soil, whereas they do not play a significant role in the diffuse degassing of CO2. The measured fluxes were used to compute the CO2 and GEM total outputs (402 and 5.41 × 10−6 t day−1, respectively) from the study area (92,000 m2) and to construct contour maps showing the spatial distribution of the ϕCO2 and ϕGEM values. By modifying the geometry of SCC and the time interval of the sampling series, the proposed method can be applied to the measurements of GEM soil fluxes in other geological systems and man-made environments. 相似文献