Sedimentary Trace Elements as Proxies to Depositional Changes Induced by a Holocene Fresh-Brackish Water Transition     

John Sternbeck  Gustav Sohlenius  Rolf O. Hallberg 《Aquatic Geochemistry》2000,6(3):325-345

A halocline developed in the GotlandDeep, Baltic Sea, at c. 8.0 ¹⁴C ky BP, as theresult of a transition from fresh to brackish water.The sediment-water interface changed from oxic topredominantly anoxic, depositional conditions wereperiodically euxinic and pyrite formation wasextensive. This environmental change led topyritization of the upper part of earlier depositedsediments. This study discusses how the distributionof trace elements (As, Ba, Cd, Cu, Co, Mo, Mn, Ni, Pb,U, Zn and V) were affected by the changing redoxconditions, productivity and salinity. The reducingconditions led to pyritization of Cu, Co, Ni, Cd, Mo,Mn and As. Lead and Zn concentrations are very low inpyrite, in agreement with their coordination tosulfide being tetrahedral. Certain elements areenriched in those sediments deposited under euxinicconditions. This enrichment was caused by scavengingof elements dissolved in the water column and isrestricted to elements that have a comparably longresidence time in the Baltic Sea. Molybdenum appearsto be the most unambigious proxy for euxinicconditions, whereas enrichment of U also requiresbrackish water in the productive zone. In the brackishenvironment, enrichment of Ba and V are linked to thecycling of organic carbon. Manganese and As are theonly elements that have been significantly remobiliseddue to the downward moving pyritization front.  相似文献   

Distal axis sulfide mineralization on the ultraslow-spreading Southwest Indian Ridge: an LA-ICP-MS study of pyrite from the East Longjing-2 hydrothermal field     

Shili Liao  Chuanwei Zhu  Jianping Zhou  Weiyong Liu  Junyu Yu  Jin Liang  Weifang Yang  Wei Li  Jia Liu  Chunhui Tao 《海洋学报(英文版)》2021,40(5):105-113

The newly discovered East Longjing-2 hydrothermal field (ELHF-2) is located on the Dragon Horn oceanic core complex of the ultraslow-spreading Southwest Indian Ridge, approximately 12 km from the ridge axis. This study measured the chemical compositions of pyrite from ELHF-2 using a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to investigate the genesis of the field. Three generations of pyrite were classified, and found that: Py1 and Py2, rich in V, Mn, U, and Se, occur in altered basalt debris and the silica alteration matrix, respectively. Py3 was mainly intergrown with chalcopyrite in quartz veins and had higher Cu, In, Ag, Sb, and Au contents than Py1 and Py2. Some elements, such as Au, Se, and Pb, are likely presented as direct substitution with Fe2+ in pyrite, while Cu, Zn, Co, Ni, and Ag probably occur both as direct substitution with Fe and as distributed micro- to nanoparticle-sized sulfides. Meanwhile, the occurrence of V, Mn, and U is likely presented as oxide inclusions. Trace element geochemistry suggested that the pyrite was formed under high-temperature conditions, and the ore forming elements were likely derived from ultramafic rocks. In addition, Py1 and Py2 were formed under higher water/rock ratio and higher temperature conditions, with more seawater involvement compared with Py3. The formation of ELHF-2 was probably driven by exothermic serpentinization reactions with an additional magmatic heat. This study shows that high-temperature hydrothermal circulation driven by magmatic activity can be developed on distal rift flank areas of magma-starved ultraslow-spreading ridges.  相似文献   

Evolution and diagenetic implications of framboids in the methane-related carbonates of the northern Okinawa Trough     

Kehong Yang  Zhimin Zhu  Yanhui Dong  Fengyou Chu  Weiyan Zhang 《海洋学报(英文版)》2021,40(12):114-124

Authigenic carbonate samples were collected from the northern Okinawa Trough. Based on their carbon and oxygen isotopes, these samples were found to be methane-related carbonates precipitated by the anaerobic oxidation of methane (AOM). Petrological analysis revealed numerous framboidal pyrites that had been partly oxidized. In order to trace the variation and diagenetic information of these framboidal pyrites, their diameters and geochemical components were studied using an electron probe. The results showed that their diameters varied from 4 μm to 17 μm (n = 60; geometric mean of 9.9 μm) and were of a normal distribution. The diameters of single pyrite that formed the framboidal pyrites varied from 1 μm to 2 μm. The framboidal pyrites with diameters of 6–14 μm accounted for ～80％ of the total. The geometric mean of 9.9 μm indicates that they are probably diagenetic pyrites that were precipitated in a lower dysoxic environment (weakly oxygenated bottom waters). The S/Fe ratio of the framboidal minerals ranged from 0 to 1.67, and the pyrite content of single framboid varied between 0％ and 86.4％. Therefore, numerous pyrites were oxygenated to iron oxides or oxyhydroxides, and were retained as pseudomorphism pyrites. The size of framboidal pyrites precipitated in cold seeps can be used to trace the redox environment; however, acquisition of additional data via investigation of different cold seeps is necessary to obtain more persuasive results.  相似文献   

Pyrite Surface after Thiobacillus ferrooxidans Leaching at 30℃     

LU Jianjun  LU Xiancai  WANG Rucheng  LI Juan  ZHU Changjian  GAO Jianfeng 《《地质学报》英文版》2006,80(3)

  相似文献   

福建紫金山矿田金、银赋存状态及黄铁矿标型研究     

鲁美  申硕果  王碧雪  张必敏  叶荣  郭东杭 《现代地质》2016,30(2):303-315

福建紫金山铜金矿床、悦洋银多金属矿床和罗卜岭斑岩型矿床同属于与陆相火山岩相关的斑岩-浅成低温热液成矿系统。通过显微镜观察、电子探针成分分析、场发射扫描电子显微镜观测和矿石元素含量分析等综合研究方法,认为紫金山铜金矿床金的赋存状态除金矿石中自然金矿物外,金还赋存于铜矿石中硫砷铜矿、蓝辉铜矿、久辉铜矿和黄铁矿中,硫砷铜矿含金性最好,金含量最高达370 μg/g;悦洋银多金属矿床银的赋存状态包括独立银矿物、亚显微银矿物和类质同象银,银的载体矿物有方铅矿、黄铁矿、黄铜矿等;黄铁矿是紫金山铜金矿床和悦洋银多金属矿床中共同存在的矿物,黄铁矿成分标型特征表明两处矿床的形成均与热液有关,与前人的研究结果一致。  相似文献   

冀东高家店金矿床成因:来自金及载金黄铁矿化学成分、流体包裹体和氢氧硫同位素的证据     

杨爱雪  吕水  许曼  邢运涛  刘海龙  韦文国  安梦莹 《矿床地质》2024,43(2):396-414

高家店金矿床位于华北克拉通北缘冀东矿集区中部,为典型的蚀变岩型金矿床,少部分为石英脉型,赋存于高家店岩体的花岗岩和闪长岩内,受断裂构造控制。为了探讨高家店金矿床的成因,文章对其开展了详细的矿床地质特征、金及载金黄铁矿化学成分、流体包裹体和氢氧硫同位素研究。结果表明,高家店金矿床热液成矿期包括4个阶段,其中Ⅱ和Ⅲ阶段为金的主要成矿阶段。黄铁矿是金的主要载体矿物,金矿物为自然金和银金矿,以独立的金矿物的形式赋存于黄铁矿中。主成矿阶段黄铁矿Fe和S含量及Fe/S元素比值揭示金矿床具有岩浆热液型的特征。主成矿阶段流体包裹体类型以富液相的两相H₂O溶液包裹体为主,其次为含CO₂三相包裹体,属中温、中低盐度流体。不同成矿阶段的流体δ¹⁸O_H2O值为1.82‰~5.60‰,δD值为-83.3‰~-55.3‰,指示流体主要来自岩浆水,并有少量大气降水混入。主成矿阶段黄铁矿δ³⁴S值为2.40‰~5.61‰,显示地幔硫或岩浆硫特征,揭示成矿物质硫主要来自于深部岩浆。综合研究认为,高家店岩体的多期次岩浆侵入活动为金成矿提供了充足的热源及成矿流体,因而高家店金矿床成因类型为岩浆热液型。  相似文献   

胶西北焦家断裂带深部载金黄铁矿标型特征研究及其地质意义     

迟乃杰  韩作振  单伟  孙雨沁  熊玉新  舒磊  刘传娥  申颖  李增胜 《地球学报》2020,41(6):949-962

胶东是我国最重要的金矿集中区, 焦家金矿带是区内最主要的金矿床分布区, 黄铁矿是焦家金矿成矿作用的贯通性矿物, 是主要的载金矿物之一。本次工作采集了焦家断裂带深部2700~3000 m内的矿体及矿化体样品, 对黄铁矿进行了晶体形态、主量元素、微量元素、EMPA面扫等研究工作。各个成矿阶段的黄铁矿晶体形态标型研究表明, 成矿I阶段黄铁矿自形-半自形, 颗粒较细小, 以细粒的立方体、五角十二面体为主; 成矿Ⅱ、Ⅲ阶段黄铁矿自形-半自形, 颗粒较粗大, 以立方体为主, 含少量五角十二面体, 具有较多的立方体、五角十二面体聚形晶; 成矿Ⅳ阶段黄铁矿主要以继承性的细粒立方体黄铁矿为主。各个成矿阶段的主、微量元素有显著的差异, 焦家深部成矿流体成矿早期Ⅰ阶段富Co、Ni, 贫Au, 成矿温度较高, 随着成矿作用的进行, 温度逐渐降低, 成矿Ⅱ阶段的成矿流体中含有一定量的伴生中温金属元素Ag、As、Te、Cu等, 成矿Ⅲ阶段中, 成矿温度进一步降低, 成矿流体逐渐转化为贫Co、Ni, 富Au及其伴生金属元素Ag、As、Te、Cu、Zn、Pb、Sb等。根据电子探针(EMPA)面扫描, 区分两种黄铁矿类型, Py1型黄铁矿, 富Co、Ni, 贫As、Pb等元素; Py2型黄铁矿, 主要为富As, 包裹部分被溶蚀的Py1型黄铁矿; 通过对焦家金矿带黄铁矿的晶体形态、主量元素、微量元素、EMPA面扫等标型特征进行详细研究, 对于深部找矿预测具有十分重要的意义。  相似文献   

Geochronology and fluid source constraints of the Songligou gold‐telluride deposit,western Henan Province,China: Analysis of genetic implications     

Peng Wang  Wei Jian  Jing‐Wen Mao  Hui‐Shou Ye  Wei‐Wei Chao  Yong‐Fei Tian  Jian‐Ming Yan 《Resource Geology》2020,70(2):169-187

The Songligou gold‐telluride deposit, located in Songxian County, western Henan Province, China, is one of many gold‐telluride deposits in the Xiaoqinling‐Xiong'ershan district. Gold orebodies occur within the Taihua Supergroup and are controlled by the WNW F101 Fault, and the fault was cut across by a granite porphyry dike. Common minerals in gold orebodies include quartz, chlorite, epidote, K‐feldspar, calcite, fluorite, sericite, phlogopite, bastnasite, pyrite, galena, chalcopyrite, sphalerite, tellurides, gold, bismuthinite, magnetite, and hematite, and pyrite is the dominant sulfide. Four mineralization stages are recognized, including pyrite‐quartz stage (I), quartz‐pyrite stage (II), gold‐telluride stage (III), and quartz‐calcite stage (IV). This work reports the Rb–Sr age of gold‐telluride‐bearing pyrite and zircon U–Pb age of granite porphyry, as well as S isotope data of pyrite and galena. The pyrite Rb–Sr isochron age is 126.6 ± 2.3 Ma (MSWD = 1.8), and the average zircon U–Pb age of granite porphyry is 166.8 ± 4.1 Ma (MSWD = 4.9). (⁸⁷Sr/⁸⁶Sr) _i values of pyrite and δ³⁴S values of sulfides vary from 0.7104 to 0.7105 and ?11.84 to 0.28‰, respectively. The obtained Rb–Sr isochron age represents the ore formation age of the Songligou gold‐telluride deposit, which is much younger than the zircon U–Pb age of the granite porphyry. Strontium and S isotopes, together with the presence of bastnaesite, suggest that the ore‐forming fluid was derived from felsic magmas with input of a mantle component and subsequently interacted with the Taihua Supergroup. Tellurium was derived from metasomatized mantle and was related to the subduction of the Shangdan oceanic crust and Izanagi plate beneath the North China Craton (NCC). This deposit is a part of the Early Cretaceous large‐scale gold mineralization in east NCC and formed in an extensional tectonic setting.  相似文献   

黄铁矿Re-Os同位素定年在金属矿床研究中的应用          下载免费PDF全文

李重阳  陈雪 《地质找矿论丛》2020,35(2):138-143

黄铁矿是地壳分布最为广泛的金属矿物,其Re-Os同位素体系在金属矿床成矿年代和示踪成矿物质来源研究中具有重要地质意义。文章简述了Re-Os同位素体系成矿定年和示踪成矿物质来源的基本原理,综述了近些年黄铁矿Re-Os同位素体系在金属矿床研究应用中取得的成果;认为该方法具有测试样品易选择、测试方法多样性等特征,但该方法目前尚存在黄铁矿样品选择的多样性、测试标样不成熟和分析结果误差较大等不足之处,有待进一步研究。  相似文献   

贵州普安矿区晚二叠世煤中贵金属元素的赋存状态和地质成因   总被引：5，自引：0，他引：5  

杨建业 《地球学报》2007,28(3):277-282

运用电感耦合等离子体质谱(ICP-MS)和逐级化学提取技术(SCET)对贵州西部普安矿区晚二叠世煤中贵金属元素的含量、赋存状态和成因机理进行了研究.结果表明,贵州普安矿区2号主采煤层的矿物组成主要为低温热液流体成因的黄铁矿和陆源碎屑成因的粘土矿物;与中国煤煤相比,该煤中Rh(38 ng/g)、Pb(640 ng/g)、Ir(9 ng/g)、Pt(98 ng/g)、Au(16 ng/g)和Ag(1620 ng/g)明显富集,其中Pb、Ir、Au的含量分别是中国煤的4.3倍、9倍和5.3倍.逐级化学提取结果表  相似文献