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1.
新疆乌恰县乌拉根新生代热卤水喷流沉积铅锌矿成因研究 总被引：18，自引：3，他引：18
乌拉根铅锌矿床是新生代卤水喷流沉积矿床，矿化分布于下第三系古新统乌拉根组第一、二岩性段，矿石结构构造兼有同生沉积及叠加改造特征，围岩蚀变为黄铁矿化、天青石化、石膏化及白云石化。通过研究表明：成矿物质铅锌来自地壳深部或上地幔，硫主要来自海水硫酸盐的还原；成矿温度为64-193℃；成矿流体盐度7.22%-20.29%WtNaCl；成矿年龄45.4-54.0M。指出成矿作用经历了三个时期：a、热卤水喷流沉积成矿斯；b、热卤水喷溢叠加成矿期；c、表生氧化淋滤富集期。 相似文献
2.
陕西驾鹿金矿床地质特征及成因探讨 总被引：1，自引：0，他引：1
姜修道 《西安地质学院学报》1995,17(2):26-31
贺鹿金矿床是小秦岭金矿带中一个比较特殊的矿床类型，产于古老韧性剪切带中，围岩蚀变强烈而广泛，尤其是成脉前的钾长石化。蚀变带及其中的石英脉控制了金矿体的产出，矿床属蚀变岩型金矿，成矿时代为燕山晚期。本文在论述矿床地质特征的基础上，通过稳定同位素研究，认为燕山期构造热事件是成矿的主导控制因素，成矿溶液来自大气降水，成矿物质则部分来自太华群，部分来自上覆中元古界高山河组，矿床成因属大气降水热液矿床。 相似文献
3.
福建570铀矿床的同位素地质特征 总被引：15，自引：0，他引：15
作者详细研究了570铀矿床的同位素特征，得出如下结论：a、成矿时间大约为89.3-107.7Ma;b.成矿溶液来自中生代的当地大气降水；c、成矿溶液中的铅、锶、钙主要来自强蚀变的熔结状流纹岩，铀来自高 溪岩体；d、成矿溶液中大量CO2丢失是沥青铀矿沉淀的主要原因。 相似文献
4.
楚雄盆地砂岩铜矿床同位素特征及矿床成因 总被引：6，自引：1，他引：6
楚雄盆地砂岩铜矿形成于白垩系高峰寺组凹地苴段、马头山组六苴段和大村段,以六苴、郝家河及大村铜矿床为代表。不论是硫同位素,还是氢氧同位素、铅同位素,六苴铜矿床和郝家河铜矿床均不相同。六苴铜矿硫化物中的硫以来自围岩为主,成矿溶液来自上部天水和建造水,成矿金属物质来自围岩,推测成岩成矿作用是主要矿化机制。而郝家河铜矿,成矿物质更多的是来自地下深处,与深部地下水循环作用有关,表明郝家河铜矿床以改造成矿为主。 相似文献
5.
椅山金矿成矿主要与燕山晚期牛心屯花岗岩有关，成矿时代为燕山晚期，成矿物质具有双重来源——地层与岩浆源。牛心屯花岗岩体内石英爆裂法系统测温资料表明，该岩体在岩浆结晶期后曾有一次普遍的中一高温热液作用——成矿热液源和成矿热源。侵入石缝组接触带的牛心屯花岗岩体的岩石化学研究表明，从岩体进入围岩的元素有Si，K，Na，Fe^3 等；围岩进入岩体的元素有Al，Mg，Ca，Fe^2 等。矿石硫同位素研究表明，重硫少、富轻硫，轻硫可能来自围岩。矿体中δ^18O研究证实矿体氧同位素大多数来自牛心屯花岗岩体，少量来自围岩。碳同位素组成特征反映金矿床内的碳来自围岩。 相似文献
6.
7.
萨瓦亚尔顿金矿床成矿物质来源的初步探讨 总被引：1，自引：1，他引：1
萨瓦亚尔顿金矿床成矿物质具有多源性。资料显示，主成矿元素金一部分来自矿区容矿地层，另一部分来自下伏地层，矿质S和C主要来自深部，特别是下伏火山岩；Pb来自于造山带。成矿溶液主要来自以大气降水为补给的地下（卤）水。 相似文献
8.
201富铀矿床氢,氧,碳,硫,铅同位素研究 总被引：5，自引：0，他引：5
产于花岗岩中的２０１铀矿床是我国花岗岩型铀矿富矿之一。本文通过氢、氧、碳、硫、铅同位素组成的研究，探讨成矿溶液和成矿物质的来源，推测成矿环境。研究结果表明，该矿床成矿流体是以大气降水为主，主要成矿物质来自前燕山期花岗岩体，可能部分来自下部地壳，成矿作用是在较稳定的物化条件下进行。 相似文献
9.
石源龙地区铀矿床的同位素地质特征 总被引：1，自引：0，他引：1
本文详细研究石源龙地区铀矿床的同位素地质特征，并由此得出：ａ．成矿时间大约为９２Ｍａ～１１５Ｍａ；ｂ．成矿溶液来自当地中生代的大气降水；ｃ．成矿溶液中锶和稀土元素的来源与南园组的流纹质熔结凝灰岩有关；ｄ．成矿过程中伴随着ＣＯ２的逸失发生了同位素交换动力学效应，而且ＣＯ２大量逸失是导致沥青铀矿沉淀的主要原因。 相似文献
10.
黔西北威宁—水城铅锌矿带动力成矿作用研究 总被引：7，自引：1，他引：7
地质地球化学证据显示，黔西北铅锌矿带铅锌主要来自基底碎屑岩系，硫来自于赋矿地层，成矿流体主要来自于构造动力压泌的地层水；初始成矿流体特征可能为中低混、较高盐度、较还原、弱酸至弱碱性，具有Ca^2 (Mg^2 )-Na^ -F^-(Cl^-)型，Pb,Zn,Ba在其中呈氟氯配合物形式搬运、地相互作用是Pb,Zn沉淀的重要因素；铅锌成矿可分为两个阶段；第一阶段主要是使原始沉积的黄铁矿层改造富化和改变矿源岩中Pb,Zn的赋存状态，第二阶段的构造动力热流泵作用使Pb,Zn叠加富集成矿。 相似文献
11.
The Bulawayan Group in the Midlands greenstone belt can be divided into three formations. The Mafic Formation is composed principally of pillowed, low-K tholeiites and minor bedded chert. The Maliyami Formation and conformably overlying Felsic Formation are composed of calc-alkaline tholeiites, andesites, and dacites with andesites dominating in the Felsic Formation. Minor rhyolite quartz porphyries and ultramafic bodies also occur in the section. The Bulawayan Group near Que Que is perhaps the least altered and metamorphosed Archean greenstone succession known. The absence of andesite and related rocks, the association of bedded chert, and the consistently low K2O, Rb, and Sr contents of Mafic Formation tholeiites suggest that they represent Archean oceanic rise tholeiites. The compositions of tholeiites and andesites of the Maliyami Formation, however, suggest that they represent an emerging arc system. The Felsic Formation is interpreted as a more advanced stage in the evolution of this arc system.Trace-element model calculations favor an origin for Mafic Formation tholeiites involving about 30% partial melting of a lherzolite source. Similar calculations are consistent with an origin for Maliyami Formation tholeiites, Maliyami and Felsic Formation andesites, and Midlands rhyolites involving, respectively, 50, 20–30, and 10% equilibrium melting of eclogite or garnet amphibolite (of Mafic Formation tholeiite composition). The low K2O, Rb, and Sr contents of Mafic Formation tholeiites suggest that they were derived from an upper mantle source as depleted in these elements as the oceanic upper mantle is today.A plate tectonic model is proposed for the Bulawayan Group in which the Mafic Formation is derived from a depleted lherzolite source beneath a spreading center in a marginalsea basin and the Maliyami and Felsic Formations and associated rhyolites are produced by partial melting of eclogite in a descending slab located west of the basin. 相似文献
12.
M. Khanehbad R. Moussavi-Harami A. Mahboubi M. Nadjafi 《Geochemistry International》2012,50(9):777-790
The Sardar Formation (Carboniferous) has a lithological variation that is characterized by sandstone, shale and limestone members. Shales of the Sardar Formation from the east central Iran have been analyzed for major elements and a number of trace elements. The shales of Sardar Formation are rich in quartz minerals and clay minerals of the bulk minerals. Clay minerals of shales are composed of illite, kaolinite and slightly montmorillonite. SiO2 versus K2O/Na2O diagram shows these shales plotted in the passive continental margin or cratonic field. Geochemical data suggest high acidic source rocks similar to granite and intermediate igneous rocks. CIA and ICV suggest semi-humid climatic conditions during depositions and indicate high chemical weathering in the source area. The geochemical parameters such as V/Cr, Ni/Co and Cu/Zn ratios indicate that these shales were deposited in oxic environment. 相似文献
13.
新疆西准噶尔萨吾尔地区阿克塔木组(新建)为一套中性火山熔岩、火山碎屑岩夹少量酸性火山熔岩建造。流纹岩LA-ICP-MS锆石U-Pb年龄为337.9±0.77Ma,属早石炭世。安山岩地球化学特征表现为高Si O2(53.42%～64.74%)、A12O3(16.05%～19.23%),富Na2O(4.05%～8.13%)贫K2O(0.36%～3.65%),富Sr(448.1×10-6～1507×10-6),低Yb(0.94×10-6～1.79×10-6)、Y(8.48×10-6～16.92×10-6),高Sr/Y比值(36.6～89.0),富集LREE,亏损HREE,弱Eu正异常,明显的Nb、Ta、Ti负异常,具有典型的埃达克岩特征,为玄武质洋壳在石榴角闪岩相高度部分熔融的产物。阿克塔木组火山岩形成于与洋内俯冲有关的岛弧环境,为早石炭世额尔齐斯-斋桑洋南向俯冲的岩浆记录。俯冲板片边缘受到来自板片窗的高温软流圈物质加热,部分熔融形成的埃达克质熔体与地幔橄榄岩发生熔体-岩石反应,从而形成埃达克岩+富Nb玄武岩组合,同时发生与之相关的Cu-Au成矿作用。阿克塔木组早石炭世埃达克岩的发现,为西准噶尔地区晚古生代岩浆活动、构造演化和金属成矿等研究提供了可靠的依据。 相似文献
14.
沱沱河盆地是冻土天然气水合物潜在分布区之一,其内发育下—中二叠统开心岭群九十道班组、上二叠统乌丽群那益雄组、上三叠统结扎群巴贡组、中—渐新统雅西措组4套烃源岩以及不同类型的火山岩。研究表明,火山岩岩石类型主要为玄武岩、玄武安山岩、安山岩、玄武质粗面安山岩和粗面安山岩。火山岩主量元素低TiO_2,Al_2O_3含量较高,K_2O含量较低,K_2ONa_2O;火山岩的稀土元素配分模式为轻稀土富集型;微量元素配分模式呈锯齿状,Ta、Nb、P_2O_5、TiO_2、Y、Yb以及铁族元素Sc、Cr、Ni亏损,综合判断青海南部沱沱河地区火山岩形成于岛弧环境。结合火山岩的地球化学特征,推断火山活动可以加快烃源岩的热成熟,进而促使有机质裂解,产生热解气,为水合物的生成提供气源条件。同时,火山岩的气孔构造发育,连通性较好,有可能成为水合物的储层。火山热液具有的高压使周围的烃源岩产生裂隙,这些裂隙不仅是水合物气源的运移通道,还可以为水合物提供形成场所和储存空间。 相似文献
15.
对四川省西昌盆地上三叠统白果湾组碎屑岩的主量元素、微量元素、稀土元素进行综合研究,得出其主量元素具有富SiO2、CaO、P2O5,贫Al2O3、TFe2O3、MgO、Na2O、K2O的特征; 微量元素具有富Zr、Cs、Th、U等特征; 稀土元素总量相对较高,轻重稀土元素分馏明显,轻稀土较重稀土相对富集,具有中等负铕异常。白果湾组物源区为长英质岩区,属于被动大陆边缘区; 白果湾期的气候经历了湿润→干旱→湿润→干旱的变化过程; 成分成熟度总体偏低,呈现高→低→高→低的变化规律,与CIA变化趋势呈负相关。本次研究为该区晚三叠世环境演化研究提供了基础资料。 相似文献
16.
对内蒙古阿巴嘎旗甘珠音敖包地区中生代火山岩进行了锆石U-Pb测年和岩石地球化学研究,对其形成时代、岩石成因及构造背景给予制约。研究区主要发育中生代满克头鄂博组酸性火山岩和梅勒图组中性火山岩。LA-ICP-MS锆石U-Pb同位素定年结果显示,2组火山岩形成年龄分别为163.6±0.6Ma和139.6Ma±0.7Ma。岩石地球化学研究表明,满克头鄂博组酸性火山岩为碱性系列,具有高硅、富碱、低TFeO、Al_2O_3、TiO_2、MgO、CaO和Na_2O的特征,轻稀土元素富集、重稀土元素亏损、轻重稀土元素分馏明显,Eu强烈亏损,大离子亲石元素Rb、Th、K明显富集,Ba、Sr明显亏损,高场强元素Nb、Ta、P、Ti强烈亏损,具有A型花岗岩特点,形成于陆壳岩石的部分熔融。梅勒图组中性火山岩亦为碱性系列岩石,富碱、富钠、贫钾,高Al2O3、TiO2、MgO,贫CaO,LREE富集,HREE亏损,轻重稀土元素分馏明显,具微弱的负Eu异常,富集大离子亲石元素(LILEs)Rb、Ba、Th、U、K等,亏损高场强元素Nb、Ta、Ti、Y、Yb、Lu等,来源于下地壳镁铁质岩石部分熔融。结合岩石学及该地区构造背景特征,认为满克头鄂博组和梅勒图组火山岩可能形成于蒙古-鄂霍茨克的俯冲作用导致的大兴安岭西坡—冀北—辽西地区加厚陆壳坍塌或拆沉作用的伸展环境。 相似文献
17.
Mohammad KHANEHBAD Reza MOUSSAVI-HARAMI Asadollah MAHBOUBI Mehdi NADJAFI Mohammad Hosein MAHMUDY GHARAIE 《《地质学报》英文版》2012,86(5):1200-1210
Geochemical analysis of sandstones from the Sardar Formation (from two stratigraphic successions) in east-central Iran were used for identification of geochemical characterization of sandstones, provenance and tectonic setting. Sandstones in the two lithostratigraphic successions have similar chemical compositions suggesting a common provenance. Bulk-rock geochemistry analysis of Carboniferous sandstones from Sardar Formation indicates that they are mainly quartz dominated and are classified as quartzarenites, sublitharenites and subarkoses, derived from acid igneous to intermediate igneous rocks. Discrimination function analysis indicates that the sandstones of Sardar Formation were derived from quartzose sedimentary provenance in a recycled orogenic setting. Also, major and trace elements in sandstones of Sardar Formation (e.g., K2O/Na2O vs. SiO2) indicate deposition in a stable passive continental margin (PM). Chemical index of alteration (CIA) for these rocks (> 65%) suggests a moderate to relatively high degree of weathering in the source area. 相似文献
18.
《Precambrian Research》2007,152(3-4):170-206
The Cauê Formation of the Paleoproterozoic Minas Supergroup hosts banded iron formations (BIFs), locally called itabirites, deposited in shallow marine passive margin settings. Two major compositional types of itabirite, dolomitic and quartz itabirites, are found in the northwestern part of QF. The former consists of alternating dolomite-rich and hematite-rich bands, whereas the latter is formed with alternating quartz-rich and hematite-rich bands. Accessory minerals are chlorite, sericite, and apatite in both types.Dolomitic and quartz itabirites have a very simple chemical composition. In the dolomitic itabirite, Fe2O3 plus CaO, MgO, and LOI range from 95.8 to 97.8%, while in the quartz itabirite, Fe2O3 plus SiO2 range from 94.4 to 99.6%. Both itabirites are highly oxidized and present Fe3+/(Fe2+ + Fe3+) ratios higher than 0.98, by far superior than the average ratios of Paleoproterozoic BIFs. Trace element concentrations in itabirites are very low, ranging from <10 to 55 ppm. Dolomite shows negative δ13C values varying from −2.5 to −0.8‰ versus PDB, while the oxygen isotope data display δ18O values varying from −12.4 to −8.5‰ versus PDB. The δ13C values of the dolomitic itabirite are in the same range of those of the overlying stromatolitic dolomites of the Gandarela Formation. C and O isotopes, REE signatures, and Y/Ho ratios suggest a marine origin for the sediments of the Cauê Formation. The HREE enrichment pattern exhibited by the itabirites shows a modern seawater REE signature overprinted by a hydrothermal pattern marked by positive Eu anomalies. Very low contents of Al2O3 and TiO2 and a strong positive correlation between them indicate a minor terrigenous component in the chemically-precipitated marine sediments of the Cauê Formation. Differences in the HREE signatures of itabirites suggest that dolomitic itabirite precipitated in shallower waters receiving sediments from the continent, while quartz itabirite precipitated in deeper waters. Sea-level fluctuations caused by marine transgression–regressions possibly contributed to changes in the composition and varied input of the terrigenous sediments. These changes are expressed by the co-existence of dolomitic, quartz, and amphibolitic itabirites in the Cauê Formation, which represent lateral and vertical facies transitions of dolomitic, cherty, and shaly BIFs, respectively. 相似文献
19.
TOHRU OHTA 《Sedimentology》2008,55(6):1687-1701
The present study examines the provenance of the Jurassic Ashikita Group distributed in south‐west Japan, which is composed of the Idenohana, Kyodomari and Sakamoto Formations. Two geochemical diagrams for provenance analysis were utilized, which incorporate full consideration of compositional modifications resulting from weathering (MFW diagram) and hydraulic sorting processes (SiO2/Al2O3–Na2O/K2O diagram). The MFW diagram delineates weathering trends of sedimentary rocks and allows estimation of the original source rock composition by tracing the weathering trends backwards to an unweathered domain. Weathering trends of the Idenohana and Kyodomari Formations extend backward to the domain of intermediate and felsic igneous rocks. In contrast, sediments of the Sakamoto Formation do not fit into a linear weathering trend, indicating that the source rock cannot be approximated to igneous rocks. On the SiO2/Al2O3–Na2O/K2O diagram, sediments are organized into compositional trends, in which the range reflects compositional variations induced by the hydraulic sorting effect. On this diagram, sediments derived from the igneous and recycled sedimentary provenances can be distinguished by reading the inclination of the trend. By utilizing this principle, source rocks of the Idenohana and Kyodomari Formations are interpreted as igneous rocks and those of the Sakamoto Formation are interpreted as recycled sedimentary rocks. Therefore, these diagrams concurrently estimate the source rock composition through quantifying and adjusting the weathering and sorting effects, and reveal a systematic transition in the provenance of the Ashikita Group. The Idenohana and Kyodomari Formations were supplied chiefly from an igneous provenance, which shifted from intermediate to felsic compositions in stratigraphic order. Whereas, sediments of the Sakamoto Formation were sourced primarily from a recycled sedimentary provenance. 相似文献
20.
The Upper Miocene shales of the Samh Formation, North Marsa Alam along the Egyptian Red Sea coastal plain were analyzed for major and selected trace elements to infer their provenance, weathering intensity, and tectonic setting. The Samh Formation consists of sandstone underlies by shale and marl intercalations. The Samh shales are texturally classified as mudstones. Mineralogically, these shales consist mainly of smectite and kaolinite, associated with non clay minerals (abundant quartz and trace of plagioclase, microcline, and halite). Compared to post-Archaean Australian shales (PAAS), the Samh shales are highly enriched in SiO2, Al2O3, and Fe2O3 and depleted in TiO2, P2O5, Na2O, MgO, and K2O contents. The K2O/Al2O3 ratio values indicate predominance of clay minerals over K-bearing minerals. Trace elements like zirconium (Zr), Cr, Pb, Sc, Rb, and Cs are positively correlated with Al2O3 indicating that these elements are likely fixed in K-feldspars and clays. The Chemical Index of Alteration (CIA), Plagioclase Index of Alteration (PIA), and Chemical Index of Weathering (CIW) values indicate moderate to intense weathering of the source material in a semiarid climate. The geochemistry results suggest that the Samh shales were deposited in a passive margin of a synrift basin and derived from felsic (granitic) source rocks. The inferred tectonic setting for the Upper Miocene Samh shales in Marsa Alam is in agreement with the tectonic evolutionary history of the Eastern Desert of Egypt during the Upper Miocene. 相似文献