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1.
As geochemical appraisals of mineral regions of commercial prospectivity evolve, the organic matter associated with metal rich ores has attracted greater attention. Petroleum basin and modern seafloor hydrothermal vent studies have suggested that organic matter can have a significant influence on the behaviour of mineralising fluids. There have been many isolated reports of certain organic compositional or morphological (e.g. pyrobitumen) features showing an apparent relationships with hydrothermal fluids or minerals, raising expectations that organic based parameters might be useful to mineral exploration. However, the understanding of organic–inorganic relationships in Earth systems is far from complete. For example, the detailed mechanics of the interaction of organics with hydrothermal fluids over geological time remain largely undefined. Organic geochemistry studies have traditionally involved the measurement and interpretation of the hydrocarbon composition of sedimentary rocks. Here we review the types of aliphatic hydrocarbons, aromatic hydrocarbons and metalloporphyrins often detected from organic geochemical investigations in mineral-rich regions. Such molecular data can be particularly diagnostic of biochemical sources and the palaeo-environments at the time mineral associated organic matter was deposited. Sub-surface trends of hydrocarbon alteration may also reflect major biogeochemical processes such as thermal maturity and biodegradation. Organic geochemistry data can also occasionally provide information about the nature (e.g., origin, composition, temperatures) and migration pathways of hydrothermal fluids and can make a contribution to holistic ore genesis models. The well preserved organic matter associated with the economic “Here's Your Chance” Pb–Zn–Ag Mine (Paleoproterozoic Barney Creek Formation, McArthur Basin, Australia) and the transition metal-rich Early Permian Kupferschiefer Formation (Germany–Poland) have attracted significant attention. A more detailed summary of the organic character of these deposits is provided to highlight the contribution organic geochemistry can make to understanding mineralisation processes. Most organic geochemical studies of highly mineralised regions, however, have not adequately addressed the significance of organic matter to mineralisation. A slightly different analytical focus than traditionally used for exploration appraisal of petroleum hydrocarbons may be required to properly evaluate the significance of organic species to the mobilisation, transport and deposition of ore metals. The characterisation and subsequent thermodynamic modeling of organic substances and complexes within metalliferous hydrothermal systems will contribute to a better understanding of the nature and role of organic–inorganic fluids or other affiliated organics in ore systems. 相似文献
2.
西太平洋冲绳海槽烟囱硫化物矿床矿石化学特征与分带型式 总被引：12，自引：0，他引：12
西太平洋冲绳海槽烟囱式硫化物矿床分布于琉球弧后扩张盆地、产于尹是名洼陷盆地（深１４００ｍ），其特征与日本黑矿类似。硫化物矿石及烟囱主要有３种化学类型：Ｐｂ－Ｚｎ－Ｂａ型、Ｚｎ－Ｐｂ型和Ｃｕ－Ｚｎ型，三者分别代表温度不断升高的热液体系的早、中、晚３个成矿阶段产物，其中，Ｐｂ－Ｚｎ－Ｂａ矿石及烟囱形成于高ｆｏ２环境和高流速、低温、富Ｐｂ、Ｚｎ、Ｂａ热液体系，Ｃｕ－Ｚｎ矿石及烟囱形成于低流速、高温、富Ｃｕ热液体系，Ｚｎ－Ｐｂ矿石则介于其间。硫化物烟囱显示明显的矿物－化学分带。在Ｐｂ－Ｚｎ－Ｂａ矿石（烟囱），Ｚｎ、Ｃｄ集中于烟囱中央，Ｂａ、Ｆｅ、Ａｓ、Ｓｂ、Ａｇ、Ｐｂ集中于烟囱外带，Ｃｕ则富集于烟囱中外部。在Ｃｕ－Ｚｎ矿石，Ａｓ、Ｓｂ、Ｆｅ、Ａｇ、Ａｕ仍富集于烟囱外带，Ｃｕ、Ｚｎ、Ｐｂ则在烟囱中央富集。依此元素化学分带型式，建立了古代黑矿硫化物矿体分带与硫化物堆积模式。 相似文献
3.
O. Yu. Bogdanova A. Yu. Lein O. M. Dara E. G. Ozhogina A. P. Lisitzin 《Doklady Earth Sciences》2016,470(1):928-932
Pyrrhotite ores forming the hydrothermal vents of the Hydrothermal Hills in the Southern Trough of the Guaymas depression were studied. A series of features pointing to the occurrence of surface and buried sulfide deposits of pyrrhotite mineralization was revealed: the presence of pyrrhotite associations to hydrocarbons of oil series; low concentrations of Cu, Zn, and Pb; the enrichment of sulfur of pyrrhotite and hydrogen sulfide of hydrothermal solutions in heavy 34S isotope by 5–7%; and the heavy isotope composition of carbon in naphthoid compounds. The results obtained allow one to suggest searching for large sulfide deposits at active rifts of high spreading and sedimentation rates, i.e., at near-continental rifts of the humid zone of avalanche sedimentation. 相似文献
4.
皖南地区上震旦统蓝田组，是银铅锌等多金属矿床的重要赋矿层位，区域地质，矿床地质和地球化学特征研究表明，银铅锌等多金属矿床是由于热水沉积作用而形成，热水沉积作用受断裂控制明显，主要呈带状沿着祁门－三阳坑一万家桥深断裂NE方向展布，热水学沉积形成了银铅锌等多金属矿床，铁锰矿床以及蓝田组底部数千平方千米含锰碳酸盐岩，这一认识不仅为皖南地区矿床的成因给予了新的解释，也为今后该区矿产资源的勘察工作提供了新的思路。 相似文献
5.
C. Trepka-Bloch 《Mineralium Deposita》1985,20(1):23-29
The Näsliden and Rävliden deposits in the Skellefte field consist of stratiform massive sulfide ores associated with submarine volcanic and clastic rocks. The ores are pretectonic. Consequently, the orebodies are considered to have formed syngenetically with deposition of the host rocks. Banding and interlayering with host sediments are common features. Cu : Zn and Zn : Pb ratios of the ores show stratigraphically and laterally defined trends. Cu : Pb : Zn ratios correspond with those found in other deposits of volcanogenic origin. Nonstratiform breccia Cu mineralizations occur directly under the massive stratiform ores in the footwall rocks where hydrothermal alteration is strongest. Ore formation took place intermittently resulting in clusters of ore systems occurring at slightly different stratigraphical levels within each deposit. 相似文献
6.
沉积盆地中与油气密切相关的金属矿床主要包括密西西比河谷型(MVT)铅锌矿床、砂页岩型铜-铀矿床、黑色页岩中的金属硫化物矿床、沉积岩容矿的金-锑-砷-汞-铊矿床等。金属矿床与(古)油气藏在空间上的密切共生/伴生关系,暗示了二者成因上的有机联系。在许多MVT铅锌矿床和砂页岩型铜矿床中,与成矿关系密切的原油及其衍生物形成于矿化前,它们为随后的金属成矿直接提供还原硫或充当硫酸盐还原反应的还原剂。在另一些情况下,某些低温热液金属矿床,特别是Au、As、Hg、Sb、Tl矿床与油气表现出同源、同运、同聚的耦合关系,金属成矿与油气成藏同时或近同时进行。与油气具不同耦合关系的金属矿床常表现出不同的特点。与成藏和/或成矿有关的盆地流体大致可分为以碳氢化合物为主的有机流体、以含金属盐水溶液为主的无机流体以及同时富含烃类和金属组分的有机成矿流体3类,盆地中的成矿、成藏作用及其耦合关系受控于这三类流体的演化过程。沉积盆地中金属矿床与油气藏空间上密切的共生/伴生关系以及成矿、成藏过程和机理的相似性,使金属与油气矿产资源的协同勘探和综合预测成为可能。 相似文献
7.
西成矿田泥盆系铅锌矿床中的有机成矿作用 总被引：17，自引：0，他引：17
西成矿田是秦岭多金属成矿带最重要的铅锌矿田之一.从有机地球化学特征、有机质和有机分子与金属元素的关系、矿石、围岩及与矿石共生的炭沥青的元素分析及有机流体萃取金属元素的模拟实验方面出发, 探讨了有机质在西成铅锌矿田形成过程中的作用.结果表明: (1) 与矿化有关的岩石(硅质岩和灰岩), 主峰碳数均为nC18, 中间支链烷烃、伽玛蜡烷、胡萝卜烷系列含量比非矿化岩石高; (2) 与矿化有关岩石(硅质岩和大理岩) 的生物母源以菌藻类低等生物为主, 并有陆源母质混入, 矿床形成于还原环境, 矿床中存在来源相同或相似的异源有机质; (3) Pb、Zn元素与芳烃、氯芳沥青“A”、非烃+沥青呈显著的负相关; 与非烃、有机硫、有机硫/(有机碳× 1.22) 比值呈正相关关系; Pb、Zn元素与正构烷烃、甾萜烷、胡萝卜烷等有机分子丰度具正相关关系, 而与w(∑C22-)/w(∑C22+)、w(三环萜烷)/w(四环萜烷)、w(C20+C21)/w(C23+C24)及w(萜烷)/w(甾烷) 等有机分子比值具负相关关系; (4) 炭沥青与围岩、矿石中子活化分析结果表明, 在后期改造成矿作用中, 炭沥青与矿石有紧密联系, 有机质和成矿元素一起在改造成矿期抵达成矿部位并参与了成矿; (5) 模拟实验表明, 在热水流体中, 有机水的加入增大了对Pb、Zn元素的溶解能力, 增加了岩样释放成矿元素的能力, 有机质在热水流体运移过程中确实对成矿元素发生了作用.在此基础上, 提出生物有机质在西成地区铅锌矿床的形成过程中发挥了重要作用. 相似文献
8.
中国北方超大型热水沉积硫化物矿床成矿模式 总被引：4，自引：0，他引：4
中国北方超大型热水沉积硫化物矿床成矿模式李英祁思敬（西安地质学院，西安７１００５４）关键词超大型矿床热水沉积作用大陆边缘盆地热旋回中国北方超大型热水沉积硫化物矿床（ＳＥＤＥＸ）集中产出于华北地台北缘西段与扬子地台北缘西段，即秦岭与狼山两区。可确定的矿... 相似文献
9.
J. Jochum 《Mineralium Deposita》2000,35(5):451-464
A mechanical decrepitation device coupled with a gas chromatograph has been used to characterize the molecular composition
of gaseous and liquid hydrocarbons contained in minerals. Application of this technique allows the identification of low-molecular-weight
n-alkanes and some aromatic hydrocarbons in sulfides and gangue minerals from epigenetic Variscan and post-Variscan lead–zinc
deposits in the Rhenish Massif, Germany. Based on the analysis of 200 samples, Variscan and post-Variscan mineralization can
be distinguished by the composition of associated hydrocarbons. Variscan sulfides and gangue minerals contain high abundancies
of methane. In contrast, n-alkanes in the C2–C9 range and aromatic hydrocarbons (benzene, toluene) are dominant in post-Variscan mineralization. The absence of high-molecular-weight
hydrocarbons in ore minerals suggests highly mature gas associated with hydrothermal activity, during which hydrothermal fluids
caused an increase in thermal maturation of organic matter and the generation of low-molecular-weight hydrocarbons in the
adjacent organic-rich rocks. The hydrocarbon compositions contained in fluid inclusions of Variscan and post-Variscan minerals
are probably governed by the maturation level of the potential source rocks. In Variscan time tectonic brines (T > 175 °C) generated predominantly methane, whereas basement brines (T < 175 °C) expelled higher-molecular-weight hydrocarbons (wet gases, condensates, aromatic hydrocarbons) from adjacent rocks
during the Mesozoic event. The specific role of hydrocarbons in sulfide precipitation via thermochemical sulfate reduction
is indicated by geochemical characteristics of organic matter associated with the Plombières Pb–Zn deposit, in eastern Belgium.
Intense alteration phenomena were observed in near-ore kerogens, compared with unaltered kerogens far from the ore body, as
well as by a very high maturity (5.40% Ro), a systematic depletion in 12C towards the vein-type mineralization, high atomic S/C ratios (0.49), and by low atomic H/C ratios (0.29). The data suggest
that hydrothermal solutions caused a drastic increase in the thermal maturation of organic matter within the adjacent wall
rock. Increased thermal maturation resulted in increased δ13C-values of organic carbon due to the preferential release of 12C. The change in the organic matter to a H-depleted and S-enriched bulk composition in association with sulfide ores strongly
suggests that thermochemical sulfate reduction was responsible for organic degradation. Thus, thermochemical sulfate reduction
probably triggered base metal sulfide precipitation in Variscan and post-Variscan ore deposits of the Rhenish Massif. Finally,
based on data from this study and previous investigations, new genetic models are presented for both Variscan and post-Variscan
mineralization in the Rhenish Massif.
Received: 15 September 1999 / Accepted: 2 December 1999 相似文献
10.
We submitted individual aliphatic and polycyclic aromatic hydrocarbons in samples of hydrothermal petroleum from Escanaba Trough to compound specific isotope analysis to trace their origins. The carbon isotope compositions of the alkanes and polycyclic aromatic hydrocarbons (means -27.5 and -24.7%, respectively) reflect a primarily terrestrial organic matter source. 相似文献
11.
胶州湾东北部海域生态环境污染状况研究 总被引：4，自引：1，他引：3
根据2004年5月和2005年5月两次对胶州湾东北部海域海水的盐度、pH、溶解氧、化学需氧量、无机氮、活性磷酸盐、铜、铅、锌、镉、多环芳烃和有机氯农药以及表层沉积物中有机碳、石油烃、硫化物、铜、铅、镉、汞、多环芳烃和有机氯农药测定结果,并结合2001年以来历史资料,对胶州湾东北部海域生态环境质量历史变化趋势进行了分析,该海域生态环境中除个别要素如活性磷酸盐、铅、镉、汞等重金属含量有所增加外,其他污染要素含量相对稳定且有下降趋势,2001—2005年该海域生态环境质量相对稳定,仅部分要素有加重趋势。 相似文献
12.
Central Fujian Rift is another new and important volcanogenic massive sulfide Pb-Zn polymetallic metallogenetic belt. In order to find out the material genesis and mineralization period of Meixian-type Pb-Zn-Ag deposits, S and Pb isotope analysis and isotope geochronology of ores and wall rocks for five major deposits are discussed. It is concluded that the composition of sulfur isotope from sulfide ore vary slightly in different deposits and the mean value is close to zero with the 834S ranging from -3.5‰ to ＋5.6‰ averaging at ＋2.0‰, which indicates that the sulfur might originate from magma or possibly erupted directly from volcano or was leached from ore-hosted volcanic rock. The lead from ores in most deposits displays radioactive genesis character （206pb/204pb〉18.140, 207Pb/204pb〉15.584, 208pb/204pb〉38.569） and lead isotope values of ores are higher than those of wall rocks, which indicates that the lead was likely leached from the ore-hosted volcanic rocks. Based on isotope data, two significant Pb-Zn metallogenesis are delineated, which are Mid- and Late-Proterozoic sedimentary exhalative metailogenesis （The single zircon U-Pb, Sm-Nd isochronal and Ar-Ar dating ages of ore- hosted wall rocks are calculated to be among 933-1788 Ma.） and Yanshanian magmatic hydrothermal superimposed and alternated metallogenesis （intrusive SHRIMP zircon U-Pb and Rb-Sr isochronal ages between 127-154 Ma）. 相似文献
13.
胶莱盆地陆源碎屑层控金矿床矿石特征研究 总被引：3，自引：0，他引：3
产于胶莱盆地内由富Au和C有机岩石组成的含矿系中的金矿床，其含矿层位为下白垩统莱阳群一套含碳陆相碎屑岩系，它控制了蓬家夼，宋家沟式金矿的展布。对两类金矿床矿石特征进行了研究及对比，它们具有相同或相似的矿物共生组合（黄铁矿－方铅矿－闪锌矿－黄铜矿－赤铁矿，自然金）及成矿元素共生组合（Au-Cu-Pb-Zn-Fe)，成矿作用均具有多期，多阶段特征，均为受胶莱盆地形成初期富Au和C有机矿源层控制，后经构造－岩浆热液及地下热液作用的沉积改造型金矿床。 相似文献
14.
云南金顶铅锌矿床中有机质的生物标志化合物特征研究表明:正构烷烃碳数分布范围较宽,有两种峰型,具弱奇偶优势;萜烷化合物相对丰度五环三萜烷三环萜烷四环萜烷;甾烷以规则甾烷为主,规则甾烷C27-C28-C29呈不对称"V"字型分布;有机质的母质来源以低等水生生源的海藻类为主,伴随有一定量的陆源高等植物组分;有机质沉积于弱氧化-弱还原低盐度环境,其成熟度较高;样品均遭受了一定程度的热解,这可能与成矿热液的热力作用有关,部分样品还遭受了生物降解作用,砂岩型矿石共生有机质的成熟度略高于角砾状矿石赋存的有机质;生物标志化合物多参数对比表明有机质来源于三叠系三合洞组碳酸盐岩地层。 相似文献
15.
湘中湘潭盆地大塘坡组锰矿是湖南重要的锰矿基地。盆地内发育一组NNE向同沉积断裂,形成了一系列凹陷带（断陷槽）,控制了沉积岩相的分布,锰矿主要产于盆地凹陷带的黑色页岩夹碳酸锰矿微相内。矿石中Co、Zn、Pb、Mo和Ba等元素丰度较高,Co/Ni、SiO2/Al2O3、(Fe+Mn)/Ti、Al/(Fe+Mn+Al)比值以及Co/Zn-(Cu+Ni+Co)和Fe-Mn-(Cu+Ni+Co)图解都揭示锰矿成矿过程中有海底热水的参与;稀土元素分布模式、Ce、Eu异常表示锰矿形成于被动大陆边缘环境,并具有热水沉积特征;碳同位素结果显示出富集碳的轻同位素的特征,反映了湘中地区锰矿中碳同位素热水沉积的特征;氧同位素计算古温度为湘中地区锰矿的低温热水沉积成因提供了有利的佐证。 相似文献
16.
PENGRunmin ZHAIYusheng 《《地质学报》英文版》2004,78(2):534-547
Most ore-forming characteristics of the Langshan-Zha‘ertaishan hydrothermal exhalation belt, which consists of the Dongshengmiao, Huogeqi, Tanyaokou and Jiashengpan large-superlarge Zn-Pb-Cu-Fe sulfide deposits, are most similar to those of Mesoproterozoic SEDEX-type provinces of the world. The characteristics include: (1) All deposits of this type in the belt occur in third-order fault-basins in the Langshan-Zha‘ertaishan aulacogen along the northern margin of the North China Platform; (2) these deposits with all their orebodies hosted in the Mesoproterozoic impure dolomite-marble and carbonaceous phyllite (or schists) have an apparent stratabound nature; ores display laminated and banded structures, showing clear depositional features; (3) there is some evidence of syn-sedimentary faulting, which to a certain extent accounts for the temporal and spatial distribution and the size of the orebodies in all deposits and the formation of intrabed conglomerates and breccias; (4) they show lateral and vertical zonation of sulfides; (5) The Cu/(Pb Zn Cu) ratio of the large and thick Pb Zn Cu orebodies gradually decreases from bottom to top; and (6) barite is interbedded with pyrites and sometimes with sphalerite. However, some characteristics such as the Co/Ni radio of the pyrites, the volcanism, for example, of the Langshan-Zha‘ertalshan metallogenic belt, are different from those of the typical SEDEX deposits of the world. The meta-basic volcanic rock in Huogeqi, the sodic bimodal volcanic rocks in the Dongshengmiao and potassic bimodal-volcanic rocks with blastoporphyfitic and blasto-glomeroporphyritic texture as well as blasto-amygdaloidal structure in the Tanyaokou deposits have been discovered in the only ore-bearing second formation of the Langshan Group in the past 10 years. The metallogeny of some deposits hosted in the Langshan Group is closely related to syn-sedimentary volcanism based on the following facts: most of the lead isotopes in sphalerite, galena, pyrite, pyrrhotite and chalcopyrite plot on both sides of the line for the mantle or between the lines for the mantle and lower crust in the lead isotope composition diagram; cobalt content of some pyrites samples is much higher than the nickel content (Co/Ni= 11.91-12.19). Some volcanic blocks and debris have been picked out from some pyritic and pyrrhotitic ores. All Zn-Pb-Cu-Fe sulfide orebodies in these deposits occur in the strata overlying metamorphic volcanic rocks in the only ore-bearing second formation. In the Jiashengpan deposit that lacks syn-sedimentary volcanic rocks in the host succession only Pb and Zn ores occur without Cu ore, but in the Dongshengmiao, Tanyaokou and Huogeqi deposits with syn-sedimentary volcanic rocks in the host succession Cu ores occur. This indicates a relatively higher ore-forming temperature. The process of synsedimentary volcanic eruption directly supplied some ore-forming elements, and resulted in secular geothermal anomaly favorable for the circulation of a submarine convective hydrothermal system, which accounts for the precipitation of deep mineralizing fluids exhaling into anoxidic basins along the syn-sedimentary fault system in the Langshan-Zha‘ertai rift. The Dongshengmiao, Tanyaokou, and Huogeqi deposits hosted in the Langshan Group appear to be a transitional type of mineral deposit between SEDEX and VMS-types but with a bias towards SEDEX, while the Jiashengpan deposit hosted in the Zha‘ertai Group is of a characteristic SEDEX type. This evidence, together with other new discoveries of Mesoproterozoic volcanic rocks and the features of lithogeny and metallogeny of the Bayun Obo deposit in the neighborhood emphasize the diversity, complexity and uniqueness of the Mesoproterozoic Langshan-Zha‘ertal-Bayun Obo ore belt. 相似文献
17.
《International Geology Review》2012,54(13):1478-1507
The Central and Eastern Taurides contain numerous carbonate-hosted Pb–Zn deposits, mainly in Devonian and Permian dolomitized reefal–stramatolitic limestones, and in massive Jurassic limestones. We present and compare new fluid inclusion and isotopic data from these ore deposits, and propose for the first time a Mississippi Valley-type (MVT) mode of origin for them. Fluid inclusion studies reveal that the ore fluids were highly saline (13–26% NaCl equiv.), chloride-rich (CaCl2) brines, and have average homogenization temperatures of 112°C, 174.5°C, and 211°C for the Celal Da?, Delikkaya, and Ayrakl? deposits, respectively. Furthermore, the δ34S values of carbonate-hosted Pb–Zn deposits in the Central and Eastern Taurides vary between –5.4‰ and?+13.70‰. This indicates a possible source of sulphur from both organic compounds and crustal materials. In contrast, stable sulphur isotope data (average δ34S –0.15‰) for the Çad?rkaya deposit, which is related to a late Eocene–Oligocene (?) granodioritic intrusion, indicates a magmatic source. The lead isotope ratios of galena for all investigated deposits are heterogeneous. In particular, with the exception of the Suçat? district, all deposits in the Eastern (Delikkaya, Ayrakl?, Denizovas?, Çad?rkaya) and Central (Katranba??, Küçüksu) Taurides have high radiogenic lead isotope values (206Pb/204Pb between 19.058 and 18.622; 207Pb/204Pb between 16.058 and 15.568; and 208Pb/204Pb between 39.869 and 38.748), typical of the upper continental crust and orogenic belts. Fluid inclusion, stable sulphur, and radiogenic lead isotope studies indicate that carbonate-hosted metal deposits in the Eastern (except for the Çad?rkaya deposit) and the Central Taurides are similar to MVT Pb–Zn deposits described elsewhere. The primary MVT deposits are associated with the Late Cretaceous–Palaeocene closure of the Tethyan Ocean, and formed during the transition from an extensional to a compressional regime. Palaeogene nappes that typically limit the exposure of ore bodies indicate a pre-Palaeocene age of ore formation. Host rock lithology, ore mineralogy, fluid inclusion, and sulphur?+?lead isotope data indicate that the metals were most probably leached from a crustal source such as clastic rocks or a crystalline massif, and transported by chloride-rich hydrothermal solutions to the site of deposition. Localization of the ore deposits on autochthonous basement highs indicates long-term basinal fluid migration, characteristic of MVT depositional processes. The primary MVT ores were oxidized in the Miocene, resulting in deposition of Zn-carbonate and Pb-sulphate–carbonate during karstification. The ores underwent multiple cycles of oxidation and, in places, were re-deposited to form clastic deposits. Modified deposits resemble the ‘wall-rock replacement’ and the ‘residual and karst fill’ of non-sulphide zinc deposits and are predominantly composed of smithsonite. 相似文献
18.
Hypogene Zn carbonate ores in the Angouran deposit,NW Iran 总被引：1，自引：0，他引：1
Maria Boni H. Albert Gilg Giuseppina Balassone Jens Schneider Cameron R. Allen Farid Moore 《Mineralium Deposita》2007,42(8):799-820
The world-class Angouran nonsulfide Zn–Pb deposit is one of the major Zn producers in Iran, with resources estimated at about
18 Mt at 28% Zn, mainly in the form of the Zn carbonate smithsonite. This study aims to characterize these carbonate ores
by means of their mineralogy and geochemistry, which has also been extended to the host rocks of mineralization and other
local carbonate rock types, including the prominent travertines in the Angouran district, as well as to the local spring waters.
Petrographical, chemical, and stable isotope (O, H, C, Sr) data indicate that the genesis of the Zn carbonate ores at Angouran
is fairly distinct from that of other “classical” nonsulfide Zn deposits that formed entirely by supergene processes. Mineralization
occurred during two successive stages, with the zinc being derived from a preexisting sulfide ore body. A first, main stage
of Zn carbonates (stage I carbonate ore) is associated with both preexisting and subordinate newly formed sulfides, whereas
a second stage is characterized by supergene carbonates (Zn and minor Pb) coexisting with oxides and hydroxides (stage II
carbonate ore). The coprecipitation of smithsonite with galena, pyrite and arsenopyrite, as well as the absence of Fe- and
Mn-oxides/hydroxides and of any discernible oxidation or dissolution of the sphalerite-rich primary sulfide ore, shows that
the fluids responsible for the main, stage I carbonate ores were relatively reduced and close to neutral to slightly basic
pH with high fCO2. Smithsonite δ18OVSMOW values from stage I carbonate ore range from 18.3 to 23.6‰, while those of stage II carbonate ore show a much smaller range
between 24.3 and 24.9‰. The δ13C values are fairly constant in smithsonite of stage I carbonate ore (3.2–6.0‰) but show a considerable spread towards lower
δ13CVPDB values (4.6 to −11.2‰) in stage II carbonate ore. This suggests a hypogene formation of stage I carbonate ore at Angouran
from low-temperature hydrothermal fluids, probably mobilized during the waning stages of Tertiary–Quaternary volcanic activity
in an environment characterized by abundant travertine systems throughout the whole region. Conversely, stage II carbonate
ore is unambiguously related to supergene weathering, as evidenced by the absence of sulfides, the presence of Fe-Mn-oxides
and arsenates, and by high δ18O values found in smithsonite II. The variable, but still relatively heavy carbon isotope values of supergene smithsonite
II, suggests only a very minor contribution by organic soil carbon, as is generally the case in supergene nonsulfide deposits. 相似文献
19.
Sedex型矿床成矿系统 总被引：53，自引：0，他引：53
系统总结了Ｓｅｄｅｘ型矿床产出的构造背景、地质环境、矿床地质地球化学特征、矿化流体来源及成矿模式等问题。结合某些最新研究成果,对该类型矿床的Ｐｂ、Ｓｉ、Ｂ同位素地球化学进行了综合研究,并以加拿大科迪勒拉地区页岩容矿的Ｚｎ Ｐｂ矿床、中国大厂锡多金属矿床及澳大利亚布罗肯希尔Ｐｂ Ｚｎ Ａｇ矿床为例,深入讨论了Ｐｂ、Ｓｉ、Ｂ的来源及其对矿床成因的指示意义。对产于不同地质环境下现代海底热液成矿系统的研究证明,有沉积物覆盖和无沉积物覆盖海底成矿热流体的化学组成及Ｐｂ、Ｓｒ、Ｂ稳定同位素地球化学明显不同。前者富含与陆壳物质有关的金属组合及ＮＨ４,并富含放射成因Ｐｂ和Ｓｒ的组分,后者富含与洋壳玄武岩有关的金属组合,但特别贫ＮＨ４。这种不同与古代Ｓｅｄｅｘ型和塞浦路斯型矿床之间化学组成的差别十分相似,它意味着前者成矿物质主要来源于下伏陆壳岩石,并为其富含Ｂ,Ｂａ,Ａｇ,Ａｓ,Ｓｂ,Ｗ,Ｓｎ,Ｈｇ,Ｍｎ等元素提供了合理的解释。在此基础上,笔者指出,在特定地球化学背景下,上述那些元素也能形成独立的Ｓｅｄｅｘ型矿床,同时强调了注意寻找这种新型矿床的重要性 相似文献
20.
A. P. Geptner Yu. I. Pikovskii L. T. Protasevich T. A. Alekseeva M. E. Ramenskaya 《Lithology and Mineral Resources》2003,38(6):509-521
Relationships of mineralized microbiota with the content of polycyclic aromatic hydrocarbons in hydrothermal systems are considered. It has been established that the mineralized microbiota can serve as an indicator of hydrothermal hydrocarbon flows in present-day and ancient deposits. 相似文献