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1.
《Resource Geology》2018,68(3):258-274
The Dabaoshan deposit in Northern Guangdong Province, South China, is a Cu–Mo–W–Pb–Zn polymetallic deposit, located in the southern part of the Qin–Hang porphyry–skarn Cu–Mo ore belt. The deposit mainly comprises porphyry Mo and stratiform skarn Cu ore deposits. The genesis of the Cu ore deposit has been ascribed to a typical skarn ore deposit formed by the metasomatism of Devonian carbonate rock layers or to a volcanic rock‐hosted massive sulfide deposit formed by marine exhalation. In this paper, we report on the homogenization temperatures and salinities of fluid inclusions and C, H, O, S, and Pb isotopic compositions of fluids and minerals in this deposit. Homogenization temperatures and salinities of fluid inclusions in garnet, diopside, quartz, and calcite provide information on the skarnification, mineralization, and postmineralization stages. The data show that ore‐forming fluids experienced a continuous transition from high temperatures and salinities to low temperatures and salinities over the entire period of mineralization. C, H, and O isotopic compositions indicate that ore‐forming fluids were derived mainly from magmatic water. O isotopic compositions indicate that ore‐forming fluids mingled with atmospheric water during the last stage of mineralization. Sulfur in the ore came mainly from deep magmatic sources. Pb isotopic compositions in the orebody show that almost all the lead in the ore was derived from magma with a crustal source. Combined geological, geophysical, and geochemical data were achieved before we proposed that the Dabaoshan porphyry–skarn Cu–Mo–W–Pb–Zn deposit, as one member of the Qin–Hang porphyry–skarn Cu–Mo ore belt, formed during the Jurassic subduction of the paleo‐Pacific plate beneath the Eurasian continent at quite low angle. NE‐ and EW‐trending structures controlled the emplacement of magmatic rocks in the South China region. In the mining area, the Xiangguanping Fault and its branches were the main conduits for magmatic crystallization and mineralization. The many subfaults, folds, and interlayer fracture zones on both sides of the main fault provided the requisite space for the ore and, together, were the controlling structures of the orebody. 相似文献
2.
成矿热液的氢、氧同位素组成与其水的类型、水/岩交换的岩石成分和同位素组成、水/岩交换时的温度及水/岩交换程度(W/R比值大小)等诸多因素有关,微生物和有机质也对其有一定的影响。因此,仅通过简单投影的方法将成矿热液的氢、氧同位素值与一些所谓的标准值进行类比,由此就推断出热液中水的来源,这种方法是不可取的;尤其当成矿热液的氢、氧同位素值介于大气降水和岩浆水的值之间时,切忌滥用两种水混合成矿模式,因为实际情况往往并不是这样。本文以胶东乳山金矿床为例,展开了这方面的讨论。 相似文献
3.
胶东金矿成矿流体同位素的地质特征 总被引：13，自引：0，他引：13
胶东大、中型金矿床成矿流体的Ｈ、Ｏ同位素组成显示出金矿床的初生成矿流体以岩浆水为主,在重熔花岗岩形成作用中继承了部分变质水,在高温阶段的成矿作用中以岩浆水为主,其后逐渐向大气降水方向演化,只有少部分矿床属大气降水成因。本文探讨了Ｈ．Ｐ．泰勒的水岩反应同位素交换质量平衡方程的应用条件,当水／岩比很小时,该方程不能确切判定关于成矿流体的成因,本文提供了以地质条件为前提的解析方法。成矿流体的Ｒｂ－Ｓｒ年龄揭示出胶东金矿主要成矿期为燕山晚期,成矿流体的ＩＳｒ与玲珑花岗质杂岩体中的郭家店、郭家岭型岩体一致,而成矿作用特别是与郭家岭型岩体重熔形成作用有关。 相似文献
4.
通过矿床地质特征、流体包裹体及氧、氢稳定同位素的研究,认为马家窑金矿属再平衡岩浆热液矿床,金青顶和十里铺金矿属大气降水热液矿床。马家窑金矿石英的δD、δ18O值高,变化小,比较稳定;蚀变岩石的δ18O在磺向上由围岩向矿脉逐渐升高。金青顶和十里铺金矿石英的δD、δ18O值低、变化大;蚀变岩石的δ18O值由地表向深部逐渐降低。开展金矿的氮稳定同泣素研究,在国内尚数首次。马家窑金矿36Ar在温度300℃以下相对含量不到10%,金青顶和十里铺金矿36Ar则达90%以上,表明前者以岩浆成因40Ar为代表,后者则以大气氩36Ar为代表,进而表明马家窑金矿是再平衡岩浆热液成因,金青顶和十里辅金矿是大气降水热液成因。示踪结果与H、O同位素一致,表明氩同位素在示踪成矿热液、矿床成因研究方面是一种较为有效的手段。 相似文献
5.
新疆东天山康古尔塔格金矿带研究 总被引：25，自引：0，他引：25
通过矿床地质和Ｒｂ－Ｓｒ法，Ｕ－Ｐｂ法，＾４０Ａｒ－＾３９Ａｒ法，Ｓｍ－Ｎｄ法生代学及氢，氧，硫，碳，锶，铅等稳定同位素与流体包裹体研究，查明东天康古尔塔格金矿带中浅成低温热液型金矿，韧性剪切带蚀变岩型金矿及花岗岩有关的石英脉型金矿三者大地构造背景相同，成矿时代一致。成矿物质来源相似，流体包裹体成分类同，属同一成矿系列，三者之间主要是成矿地质环境不尽相同，成矿元素组合有差异，控矿构造不同，反映成矿 相似文献
6.
Electron microprobe analyses of gold and associated ore minerals as well as stable isotope analyses of sulphide and carbonate minerals were performed in order to determine the metal and fluid sources and temperature of the mineralizing systems to better understand the genesis of the Atud gold deposit hosted in the metagabbro–diorite complex of Gabal Atud (Central Eastern Desert, Egypt). The gold can be classified as electrum (63.6–74.3 wt.% Au and 24.6–26.6 wt.% Ag) and is associated with arsenopyrite and As-bearing pyrite in the main mineralization (gold-sulphides) phase within the main mineralized quartz veins and altered host rocks. Based on the arsenopyrite geothermometer, As-contents (29.3–32.7 atom%) in arsenopyrite point to deposition in the Log ?S2 and T ranges of ?10.5 to ?5.5 and 305–450°C, respectively, during the main mineralizing phase. Based on the δ34S isotopic compositions of the sulphides, they are originated from magmatic fluids in which the sulphur is either sourced directly from magma or remobilized from the magmatic rocks (gabbroic rocks). On the other hand, calcite formed from fluids having mainly magmatic mixed with variable metamorphic signatures based on its δ13C and δ18O values. This work concluded that the gold-bearing ores at Atud deposit have magmatic sources leaching from the country intrusive rocks during water/rock interactions then remobilized during a metamorphic event. Therefore, the Atud gold deposit is classified as an intrusion-related gold deposit, in which the gabbro–diorite host intrusion acted as the source of metals which were mobilized and deposited as a result of the effects of NW–SE shearing. 相似文献
7.
8.
新疆东准噶尔松喀尔苏铜金矿区斑岩型矿床成因研究 总被引：1，自引：0，他引：1
松喀尔苏铜金矿区位于卡拉麦里石炭纪陆相火山岩带。文章通过矿床地质、围岩蚀变、含矿斑岩、流体包裹体和同位素研究,探讨了矿床成因类型。研究表明,松喀尔苏矿床具斑岩型矿床的特征,铜金矿化体产于岩体接触带,围岩蚀变具有分带性,从岩体向围岩依次发育绢英岩化带、高岭石化带和青磐岩化带,绢英岩化带与成矿相关。含矿斑岩复式岩体系同期陆相火山活动产物,成矿作用在时间、空间和成因上与复式岩体中晚期花岗斑岩有关。花岗斑岩具有富水、富挥发性组分和岩浆爆破作用的氧化性岩浆特点,具有后碰撞花岗岩类的地球化学亲缘性,其岩浆起源于后碰撞挤压-伸展转换期的壳-幔岩浆过渡带。幔源岩浆注入、软流圈地幔底侵作用和壳-幔岩浆混合作用是形成含矿斑岩岩浆的主导因素。流体包裹体包括液相包裹体、气相包裹体和含子晶多相包裹体,激光拉曼探针分析表明,气相成分以CO2和CH4为主。成矿流体具有从高温、高盐度岩浆体系向低温、低盐度与大气降水混合的演化过程,流体沸腾或不混溶作用及温度、盐度降低是导致流体中成矿物质沉淀的主要因素。氢、氧同位素组成表明成矿流体以岩浆水为主,在成矿晚期混有大气降水。硫同位素具幔源硫的特征。铅同位素组成显示成矿作用起源于下地壳-上地幔过渡带的岩浆作用。综上所述,该矿床属于与陆相火山-侵入岩有关的斑岩型铜金矿床。 相似文献
9.
Zhenjun Sun Zongqi Wang Henan Yu Chengyang Wang Guanghu Liu Xaingdong Bai 《Resource Geology》2019,69(1):1-21
The Zhuanshanzi gold deposit lies in the eastern section of the Xingmeng orogenic belt and the northern section of the Chifeng‐Chaoyang gold belt. The gold veins are strictly controlled by a NW‐oriented shear fault zone. Quartz veins and altered tectonic rock‐type gold veins are the main vein types. The deposits can be divided into four mineralization stages, and the second and third metallogenic stages are the main metallogenic stages. In this paper, based on the detailed field geological surveys, an analysis of the orebody and ore characteristics, microtemperature measurement of fluid inclusions, the Laser Raman spectrum of the inclusions, determination of C? H? O? S? Pb isotopic geochemical characteristics, and so on were carried out to explore the origin of the ore‐forming fluids, ore‐forming materials, and the genesis of the deposits. The results show that the fluid inclusions can be divided into four types: type I – gas–liquid two‐phase inclusions; type II – gas‐rich inclusions; type III– liquid inclusions; and type IV – CO2‐containing three‐phase inclusions. However, they are dominated by type Ib – gas liquid inclusions and type IV – three‐phase inclusions containing CO2. The gas compositions are mainly H2O and CO2, indicating that the metallogenic system is a CO2? H2O? NaCl system. The homogenization temperature of the ore‐forming fluid evolved from a middle temperature to a low temperature, and the temperature of the fluid was further reduced due to meteoric water mixing during the late stage, as well as a lack of CO2 components, and eventually evolved into a simple NaCl? H2O hydrothermal system. C? H? O? S? Pb isotope research proved that the ore‐forming fluids are mainly magmatic water during the early stage, with abundant meteoric water mixed in during the late stage. Ore‐forming materials originated mostly from hypomagma and were possibly influenced by the surrounding rocks, suggesting that the ore‐forming materials were mainly magmatic hydrothermal deposits, with a small amount of crustal component. The fluid immiscibility and the CO2 and CH4 gases in the fluids played an active and important role in the precipitation and enrichment of Au during different metallogenic stages. The deposit is considered a magmatic hydrothermal deposit of middle–low temperature. 相似文献
10.
Feng Yang Wei Zhai Xiaoming Sun Reiner Klemd Yanyan Sun Yunshan Wu Renmin Hua Siqi Zheng 《Resource Geology》2019,69(1):107-122
The Yaoling tungsten deposit is a typical wolframite quartz vein‐type tungsten deposit in the South China metallogenic province. The wolframite‐bearing quartz veins mainly occur in Cambrian to Ordovician host rocks or in Mesozoic granitic rocks and are controlled by the west‐north‐west trending extensional faults. The ore mineralization mainly comprises wolframite and variable amounts of molybdenite, chalcopyrite, pyrite, fluorite, and tourmaline. Hydrothermal alteration is well developed at the Yaoling tungsten deposit, including greisenization, silicification, fluoritization, and tourmalinization. Three types of primary/pseudosecondary fluid inclusions have been identified in vein quartz, which is intimately intergrown with wolframite. These include two‐phase liquid‐rich aqueous inclusions (type I), two‐ or three‐phase CO2‐rich inclusions (type II), and type III daughter mineral‐bearing multiphase high‐salinity aqueous inclusions. Microthermometric measurements reveal consistent moderate homogenization temperatures (peak values from 200 to 280°C), and low to high salinities (1.3–39 wt % NaCl equiv.) for the type I, type II, and type III inclusions, where the CO2‐rich type II inclusions display trace amounts of CH4 and N2. The ore‐forming fluids are far more saline than those of other tungsten deposits reported in South China. The estimated maximum trapping pressure of the ore‐forming fluids is about 1230–1760 bar, corresponding to a lithostatic depth of 4.0–5.8 km. The δDH2O isotopic compositions of the inclusion fluid ranges from ?66.7 to ?47.8‰, with δ18OH2O values between 1.63 and 4.17‰, δ13C values of ?6.5–0.8‰, and δ34S values between ?1.98 and 1.92‰, with an average of ?0.07‰. The stable isotope data imply that the ore‐forming fluids of the Yaoling tungsten deposit were mainly derived from crustal magmatic fluids with some involvement of meteoric water. Fluid immiscibility and fluid–rock interaction are thought to have been the main mechanisms for tungsten precipitation at Yaoling. 相似文献
11.
蔡家营铅—锌—银矿床的稳定同位素地球化学研究 总被引：3，自引：0，他引：3
河北蔡家营矿床是大型中温热液充填－交代脉型铅－锌－银矿床。其硫化物的δ＾３４Ｓ值为２．２‰－７．８‰，同世代共存的１０个硫化物对的Δ＾３４Ｓ值表明，Ｆｅ－（Ｚｎ、Ｐｂ）－Ｓ系统的硫同位素非平衡分馏占主导，硫是岩浆（为主）与老变质岩层硫的混合来源。石英及其流体包裹体的δ＾１８ＯＳＭＯＷ和δＤＳＭＯＷ值（‰）按混合模式计算表明，成矿流体为混合的岩浆和大气降水，早期成矿流体以岩浆为主，尔后则变为以大气降 相似文献
12.
夏杖子金矿床中矿物包裹体水的氢、氧同位素分别为：δD=-91.7‰——73.1‰,δ18OH2o=5.68‰-6.23‰,说明读矿床的成矿溶液是来源于岩浆水和大气降水;矿物的硫同位素组成基本上全是负值,且变化范田较小,同位素平衡温度平均为208-240℃,成矿溶液总硫平均同位素组成-19.70‰——20.64‰,证明成矿热液中H2S原子团占优势,其硫源可能为本区结晶基底;石英中流体包裹体Rb-Sr同位素等时年龄为105±7.2Ma,说明其成矿时代为燕山晚期。综合分析认为,该矿床为与岩浆热液有关的中-低温热液脉型金矿床。 相似文献
13.
The Sin Quyen-Lung Po district is an important Cu metallogenic province in Vietnam, but there are few temporal and genetic constraints on deposits from this belt. Suoi Thau is one of the representative Cu deposits associated with granitic intrusion. The deposit consists of ore bodies in altered granite or along the contact zone between granite and Proterozoic meta-sedimentary rocks. The Cu-bearing intrusion is sub-alkaline I-type granite. It has a zircon U-Pb age of ~776 Ma, and has subduction-related geochemical signatures. Geochemical analysis reveals that the intrusion may be formed by melting of mafic lower crust in a subduction regime. Three stages of alteration and mineralization are identified in the Suoi Thau deposit, i.e., potassic alteration; silicification and Cu mineralization; and phyllic alteration. Two-phase aqueous fluid inclusions in quartz from silicification stage show wide ranges of homogenization temperatures(140–383℃) and salinities(4.18wt%–19.13wt%). The high temperature and high salinity natures of some inclusions are consistent with a magmatic derivation of the fluids, which is also supported by the H-O-S isotopes. Fluids in quartz have δD values of –41.9‰ to –68.8‰. The fluids in isotopic equilibrium with quartz have δ~(18)O values ranging from 7.9‰ to 9.2‰. These values are just plotted in the compositional field of magmatichydrothermal fluids in the δD_(water) versus δ~(18)O_(water) diagram. Sulfide minerals have relatively uniform δ~(34)S values from 1.84‰ to 3.57‰, which is supportive of a magmatic derivation of sulfur. The fluid inclusions with relatively low temperatures and salinities most probably represent variably cooled magmatic-hydrothermal fluids. The magmatic derivation of fluids and the close spatial relationship between Cu ore bodies and intrusion suggest that the Cu mineralization most likely had a genetic association with granite. The Suoi Thau deposit, together with other deposits in the region, may define a Neoproterozoic subduction-related ore-forming belt. 相似文献
14.
The Ciemas gold deposit is located in West Java of Indonesia,which is a Cenozoic magmatism belt resulting from the Indo-Australian plate subducting under the Eurasian plate.Two different volcanic rock belts and associated epithermal deposits are distributed in West Java:the younger late Miocene-Pliocene magmatic belt generated the Pliocene-Pleistocene epithermal deposits,while the older late Eocene-early Miocene magmatic belt generated the Miocene epithermal deposits.To constrain the physico-chemical conditions and the origin of the ore fluid in Ciemas,a detailed study of ore petrography,fluid inclusions,laser Raman spectroscopy,oxygen-hydrogen isotopes for quartz was conducted.The results show that hydrothermal pyrite and quartz are widespread,hydrothermal alteration is well developed,and that leaching structures such as vuggy rocks and extension structures such as comb quartz are common.Fluid inclusions in quartz are mainly liquid-rich two phase inclusions,with fluid compositions in the NaCl-H20 fluid system,and contain no or little CO_2.Their homogenization temperatures cluster around 240℃-320℃,the salinities lie in the range of 14-17 wt.%NaCl equiv,and the calculated fluid densities are 0.65-1.00 g/cm~3.The values of δ~(18)O_(H2O-VSMOW)for quartz range from +5.5‰ to +7.7‰,the δD_(VSMOW) of fluid inclusions in quartz ranges from-70‰ to-115‰.All of these data indicate that mixing of magmatic fluid with meteoric water resulted in the formation of the Ciemas deposit.A comparison among gold deposits of West Java suggests that Miocene epithermal ore deposits in the southernmost part of West Java were more affected by magmatic fluids and exhibit a higher degree of sulfldation than those of Pliocene-Pleistocene. 相似文献
15.
GONG Xiaodong YAN Guangsheng YE Tianzhu ZHU Xinyou LI Yongsheng ZHANG Zhihui JIA Wenbin YAO Xiaofeng 《《地质学报》英文版》2015,89(3):822-835
The Dahutang tungsten polymetallic ore field is located north of the Nanling W-Sn polymetallic metallogenic belt and south of the Middle—Lower Yangtze River Valley Cu-Mo-Au-Fe porphyry-skarn belt.It is a newly discovered ore field,and probably represents the largest tungsten mineralization district in the world.The Shimensi deposit is one of the mineral deposits in the Dahutang ore field,and is associated with Yanshanian granites intruding into a Neoproterozoic granodiorite batholith.On the basis of geologic studies,this paper presents new petrographic,microthermometric,laser Raman spectroscopic and hydrogen and oxygen isotopic studies of fluid inclusions from the Shimensi deposit.The results show that there are three types of fluid inclusions in quartz from various mineralization stages:liquid-rich two-phase fluid inclusions,vapor-rich two-phase fluid inclusions,and three-phase fluid inclusions containing a solid crystal,with the vast majority being liquid-rich two-phase fluid inclusions.In addition,melt and melt-fluid inclusions were also found in quartz from pegmatoid bodies in the margin of the Yanshanian intrusion.The homogenization temperatures of liquid-rich two-phase fluid inclusions in quartz range from 162 to 363℃ and salinities are 0.5wt%-9.5wt%NaCI equivalent.From the early to late mineralization stages,with the decreasing of the homogenization temperature,the salinity also shows a decreasing trend.The ore-forming fluids can be approximated by a NaCl-H_2O fluid system,with small amounts of volatile components including CO_2,CH_4 and N_2,as suggested by Laser Raman spectroscopic analyses.The hydrogen and oxygen isotope data show that δ5D_(V-smow) values of bulk fluid inclusions in quartz from various mineralization stages vary from-63.8‰ to-108.4‰,and the δ~(18)O_(H2O) values calculated from the δ~(18)O_(V-)smow values of quartz vary from-2.28‰ to 7.21‰.These H-O isotopic data are interpreted to indicate that the ore-forming fluids are mainly composed of magmatic water in the early stage,and meteoric water was added and participated in mineralization in the late stage.Integrating the geological characteristics and analytical data,we propose that the ore-forming fluids of the Shimensi deposit were mainly derived from Yanshanian granitic magma,the evolution of which resulted in highly differentiated melt,as recorded by melt and melt-fluid inclusions in pegmatoid quartz,and high concentrations of metals in the fluids.Cooling of the ore-forming fluids and mixing with meteoric water may be the key factors that led to mineralization in the Dahutang tungsten polymetallic ore field. 相似文献
16.
SEDEX型矿床成矿流体的研究是矿床地球化学研究的重要课题之一。正确识别系统中不同的流体来源及其混合过程,是深刻理解SEDEX型矿床形成演化的关键。系统总结了国内几个典型的SEDEX型矿床同位素研究成果,认为B和Si同位素是根据SEDEX型矿床独特的矿物组合而提出的一种示踪方法,对矿床成因和沉积环境示踪效果理想;He、Ar同位素则因为在地壳和地幔储库中有极不相同的组成,是理想的幔源流体示踪剂。鉴于SEDEX型矿床含有电气石、黄铁矿、硅质岩等特殊的矿物与岩石组合,B、Si、He-Ar同位素可能更适合SEDEX型矿床矿化流体来源研究,并指出其理论发展的薄弱之处。 相似文献
17.
Hydrogen Isotope Study of Fluid Inclusions in Vein Quartz of the Hishikari Gold Deposits, Japan 总被引：1，自引：0，他引：1
Abstract: The origin of mineralizing fluids responsible for the Hishikari vein-type epithermal Au deposits was studied on the basis of the hydrogen isotopic ratio (δD) of the inclusion fluid from vein quartz and adularia. The origin of hydrothermal fluids was estimated by combination of the present δ values and the oxygen isotopic ratios (δ18O) previously reported by Shikazono and Nagayama (1993). The water in the fluid inclusions was extracted by means of decrepitation of quartz at 500°C. Hydrogen was obtained by reduction of the collected water with Zn shot at 450°C. The δD values were determined by mass spectrometer. The δD values of inclusion fluid obtained from quartz range from –61 to –114%. These are significantly lower than the δD value of the thermal water presently venting from the Hishikari deposits and that of local meteoric water. Hydrogen isotopic fractionation between water and amorphous silica, which might have initially precipitated from the hydrothermal fluids at least partly, is not a probable cause of this isotopic depletion, while some water might have been released from the initial hydrous amorphous silica during recrystallization to quartz observed presently. Thus, a part of ore fluids for the Hishikari deposits is supposed to have been originated from the water having anomalous δD values of lower than –100%. Such D depletion cannot be caused by simple oxygen-shift of meteoric water or by contribution of magmatic volatiles. The δD values of water released from the shale samples of the Shimanto–Supergroup, a major host to the Hishikari veins range from –132 to –148%. Therefore, the anomalous δD values of inclusion fluids from some vein quartz and adularia suggest that the water released from hydrous minerals of the sedimentary basement rocks by dehydration or the groundwater isotopically exchanged with sedimentary rocks at elevated temperatures during circulation, partly contributed to the hydrothermal fluids responsible for the Hishikari deposits. 相似文献
18.
维拉斯托铅锌矿床发育在大兴安岭南段西坡成矿带内。矿区出露的岩浆岩主要为石英闪长岩、花岗闪长岩以及碱性花岗岩等;矿体严格受断裂构造控制,属典型的热液脉型矿床。矿床的热液期可划分为3个阶段:Ⅰ石英-毒砂-黄铁矿阶段、Ⅱ多金属硫化物-石英阶段和Ⅲ石英-碳酸盐阶段。流体包裹体研究表明,维拉斯托矿床矿石主要发育气液两相、富CH_4以及含CH_4-CO_2的包裹体。Ⅰ阶段3种类型包裹体均发育,Ⅱ阶段以气液两相和含CH_4-CO_2的包裹体为主,Ⅲ阶段仅发育气液两相包裹体。Ⅰ阶段包裹体均一温度范围为243.1℃~398.5℃,盐度为4.8%~12%NaCleqv;Ⅱ阶段均一温度为190.0℃~331.1℃,盐度为3.5%~9.1%NaCleqv;Ⅲ阶段均一温度范围为180.0℃~240.0℃,盐度范围为3.7%~6.7%NaCleqv,显示成矿流体具有中温、低盐度和低密度的特点;激光拉曼光谱分析包裹体气相成分主要为CO_2、CH_4和H_2O。氢、氧同位素分析结果表明成矿流体具有岩浆水和大气降水的混合特征;硫同位素结果显示成矿物质具有深源的特点。综合分析认为,矿床的形成与燕山期中酸性岩浆活动密切相关,深部岩浆在上升过程中与下渗的大气降水发生混合,导致矿物质在近东西向的"S"型压扭性断裂中沉淀并富集成矿。 相似文献
19.
《Resource Geology》2018,68(3):303-325
The Lujing uranium deposit, located in the southeastern part of the Nanling metallogenic province, is one of the representative granite‐related hydrothermal uranium deposits in South China. Basic geology, geochemistry, and geochronology of the deposit have been extensively studied. However, there is still a chronic lack of systematic research on the genesis and metallogenic process of the deposit. Thus, we recently carried out an electron microprobe and stable isotopic analysis. The main research results and progresses are as follows: Uranium minerals in this deposit include coffinite, pitchblende, and uranothorite, and small amounts of uranium exist in accessory minerals in the form of isomorphism. Coffinite, which occurs predominantly as the pseudomorphs after pitchblende, also occurs as a primary mineral and is locally formed from the remobilization of uranium from adjacent uranium‐bearing minerals. The mineralizing fluid was originally composed of a magmatic fluid generated by late Yanshanian magmatism. The high As content of pyrite in ores may reflect the addition of meteoric water, or the formation water (or both), to the magmatic hydrothermal system. The δ34S values vary from −14.4‰ to 13.9‰ (mean δ34S = −3.9‰), showing a range that is similar to nearby Cambrian metamorphic strata and Indosinian granites, indicating that these host rocks represent the source of sulfur; however, the possibility of a mantle source cannot be completely ruled out. According to our new isotopic data and recent Pb isotopic data, we conclude that the uranium in ores was derived by leaching dominantly from the uranium‐rich host rocks, especially the Cambrian metamorphic strata. The δ13CPDB values (−8.75‰ to 1.40‰; mean δ13CPDB = −5.41‰) and δ18OSMOW values (5.45–18.62‰; mean δ18O = 13.02‰) of reddish calcite from the ore‐forming stage suggest that the CO2 in the mineralizing fluids was derived predominantly from the mantle, with a small component contributed by marine carbonates. Based on these new data and previous research results, this paper proposes that uranium metallogenesis in the Lujing deposit is closely associated with mafic magmatism resulting from crustal extension during the Cretaceous to Paleogene in South China. 相似文献
20.
Classic porphyry Cu–Mo deposits are mostly characterized by close temporal and spatial relationships between Cu and Mo mineralization. The northern Dabate Cu–Mo deposit is a newly discovered porphyry Cu–Mo polymetallic deposit in western Tianshan, northwest China. The Cu mineralization postdates the Mo mineralization and is located in shallower levels in the deposit, which is different from most classic porphyry Cu–Mo deposits. Detailed field investigations, together with microthermometry, laser Raman spectroscopy, and O‐isotope studies of fluid inclusions, were conducted to investigate the origin and evolution of ore‐forming fluids from the main Mo to main Cu stage of mineralization in the deposit. The results show that the ore‐forming fluids of the main Mo stage belonged to an NaCl + H2O system of medium to high temperatures (280–310°C) and low salinities (2–4 wt% NaCl equivalent (eq.)), whereas that of the main Cu stage belonged to an F‐rich NaCl + CO2 + H2O system of medium to high temperatures (230–260°C) and medium to low salinities (4–10 wt% NaCl eq.). The δ18O values of the ore‐forming fluids decrease from 3.7–7.8‰ in the main Mo stage to ?7.5 to ?2.9‰ in the main Cu stage. These data indicate that the separation of Cu and Mo was closely related to a large‐scale vapor–brine separation of the early ore‐forming fluids, which produced the Mo‐bearing and Cu‐bearing fluids. Subsequently, the relatively reducing (CH4‐rich) Mo‐bearing, ore‐forming fluids, dominantly of magmatic origin, caused mineralization in the rhyolite porphyry due to fluid boiling, whereas the relatively oxidizing (CO2‐rich) Cu‐bearing, ore‐forming fluids mixed with meteoric water and precipitated chalcopyrite within the crushed zone at the contact between rhyolite porphyry and wall rock. We suggest that the separation of Cu and Mo in the deposit may be attributed to differences in the chemical properties of Cu and Mo, large‐scale vapor–brine separation of early ore‐forming fluids, and changes in oxygen fugacity. 相似文献