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赣北大湖塘矿集区超大型钨矿地质特征及成因探讨 总被引：23，自引：11，他引：12
江西北部大湖塘地区发现世界级超大型钨矿床,使赣北成为继赣南之后我国又一重要的钨成矿省。大湖塘矿集区包括北区、南区和大雾塘矿区,正在开采的矿床有北区的石门寺矿床(己探明WO3金属量为74.255×104t)和南区的狮尾洞矿床(己探明WO3金属量31.09×104t),正在找矿勘查的矿区有北区的大岭上、大雾塘矿区平苗、东陡崖、一矿带等。矿化类型有细脉浸染型、石英大脉型、蚀变花岗岩型、云英岩型及隐爆角砾岩型钨(铜、钼)矿等多种类型,黑钨矿与白钨矿矿体共存、钨铜共生是该矿区成矿的显著特征。区内出露的沉积地层为新元古代双桥山群浅变质岩,岩浆岩为晋宁期的黑云母花岗闪长岩和燕山期多种岩性的花岗岩。燕山期主要有两期,早期为斑状花岗岩,成岩年龄约144Ma,如狮尾洞矿床的似斑状白云母(二云母)花岗岩、石门寺矿床的斑状黑云母花岗岩等,晚期为狮尾洞和大岭上矿床产出的中细粒花岗岩或花岗斑岩,成岩年龄约135~130Ma。这些岩浆的源区很可能来源于双桥山群的泥质变质沉积岩。富钨铜等成矿元素的双桥山群泥质变质岩部分熔融可初步形成含矿花岗岩浆,岩浆在高度结晶分异过程中则可使得钨铜等金属进一步富集在岩浆热液中,通过两期岩浆与成矿作用,最终形成超大型的大湖塘钨矿床。 相似文献
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为了解卡尔却卡铜多金属矿床的物质来源, 探讨其成岩、成矿机制, 通过现场调查, 结合矿床地质成矿条件, 对矿区典型的岩浆岩、围岩及矿石进行了主量元素、微量元素分析及S、Pb同位素分析.结果表明: 矿区岩体属中酸性岩, 为高钾钙碱性系列岩石, 源于深部, 上侵时受地壳混染, 具同源特征.不同地质体稀土配分曲线均为右倾轻稀土富集型, 岩浆岩、矽卡岩和矿石为同一成矿系统.微量元素地球化学显示矿区花岗岩产于火山弧环境.矿石硫同位素δ34SCDT值为4.4×10-3~11.0×10-3, 处于岩浆硫跟围岩混合硫范围内, 成矿物质具多源性.矿石铅同位素Th/U值范围为3.46~3.69, μ值为9.46~9.52, 均低于9.58, 介于地壳与原始地幔值之间, 反应矿石铅具深源铅和壳源铅特征.铅同位素特征参数示踪、构造模式示踪和Δβ-Δγ图解示踪的结果表明: 铅来源与岩浆作用有关, 以壳源铅为主并混合少量深源地幔铅.总结矿床地球化学特征表明成矿物质主要来源于岩浆, 少量来源于周围地层.矿区岩体成矿演化过程复杂, 在岩体中形成斑岩型铜、钼矿化, 在与碳酸盐岩接触带形成矽卡岩型铅、锌矿化, 及至后期热液作用形成中低温热液脉型金矿化, 是一个多因复成矿床. 相似文献
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笔者测定和解释了安徽铜陵地区赋存于中、上石炭统中的块状硫-铁-金矿床矿石铅和与成矿关系密切的闪长岩体长石铅以及该地层(围岩)全岩铅等的同位素比值及变化特征;通过这些地质体铅同位素特征的对比,提出该地区这种矿床的成矿物质来源于地层;同时通过同一矿床不同矿化类型矿石铅同位素的测定,表明不同矿化类型具有明显不同的铅同位素特征,显示出铅同位素方法利用在矿产勘探中的潜力。 相似文献
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大湖塘钨铜多金属矿整装勘查区位于江南古岛弧造山带的中段,成矿区划上属于江南地块中生代铜钼金银铅锌成矿带的“九岭—鄣公山钨锡多金属成矿亚带”。区内石门寺、狮尾洞、大湖塘三个矿段紧密相连,成矿条件相似,实际上应是一个超大型钨矿床（大湖塘钨矿床）。在该区内近年取得重大找矿突破,截止目前大湖塘钨矿床已获得WO3金属量共计1.1047Mt、Cu金属量0.652Mt伴生钼金属量56.6kt、伴生锡金属量29.4kt,伴生银1135t。值得指出的是,大湖塘矿床已探明WO3储量已接近整个赣南探明的WO3储量（约1.50Mt）,并大大高于其保有WO3储量（约0.50Mt）。这一地区的勘查工作完成后,WO3储量有望达到2.00Mt以上,可占到世界探明储量的约1/5 ~ 1/4,将赶超现世界上已知的最大钨矿集区—哈萨克斯坦的“卡拉奥巴—阿克莫亚—凯拉克特” 矿集区。因此查明大湖塘矿床成矿地质背景和矿床成因机制,对于对于进一步扩大找矿远景,进行区内钨铜资源成矿潜力预测有着现实而重要的意义。 相似文献
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《吉林大学学报(地球科学版)》2015,(Z1)
通过对莲花芯铜钼矿床地质、物化探、钻探等资料收集整理,对矿区内的地层、构造、岩浆岩分布及其地质特征、矿体的空间分布,矿石的物质组成,结构构造、围岩蚀变、矿床成因等情况进行系统的总结。对控矿构造进行了探讨,确定了矿床主要的控制因素是构造,导矿构造是近东西向,运矿构造为区内北东、北西向两组构造,而容矿构造是破碎带内呈反"S"扭动构造,区内有利的成矿构造应为北西向与北东向构造交汇部位;通过稳定同位素地球化学特征,确定了矿床形成的时代,运用不同元素稳定同位素示踪法,指出了成矿物质的来源是地幔;通过与大湖塘钨矿在成矿物质来源及成矿时代的对比研究,认为莲花芯铜钼矿赋存的围岩不是矿体的成矿母岩,其成矿母岩及成矿热液均来源于地幔,成矿母岩是同一构造背景条件下,与大湖塘特大型钨矿具有成因联系的燕山期花岗岩;指出以寻找燕山期岩浆岩为前提,找与大湖塘钨矿同类型的隐爆角砾岩型或斑岩型铜钼矿床。 相似文献
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通过对矿床矿石铅同位素组成的分析,并与矿区岩浆岩脉和围岩地层中的岩石铅同位素组成进行对比,借以示踪矿床成矿物质来源。研究表明,矿石铅与矿区岩石铅(灰岩和脉岩)的铅同位素组成具有较相近和较窄的变化范围,暗示铅可能属同一铅源。在铅同位素构造模式图及不同成因类型矿石铅的Δγ-Δβ成因分类图解中,显示出造山带铅、地壳与地幔混合的俯冲带岩浆作用铅特征,说明铅不是单一来源的正常铅,而是混合型多来源的异常铅。成矿物质是多来源的,赋矿地层和岩浆岩共同提供了铅源及成矿物质,但以岩浆为主,地层为辅,地幔铅参与了成矿。 相似文献
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西藏申扎县甲岗雪山钨、钼、铋多金属矿床稳定同位素地球化学特征及矿床成因探讨 总被引：2，自引：0，他引：2
冈底斯成矿带是西藏重要的多金属成矿区之一,在该成矿带北部申扎县首次发现的甲岗雪山钨、钼、铋多金属矿床是不同于其南部斑岩型铜多金属矿床的成矿新类型,该矿床的发现是藏北地区内生金属矿找矿的重要突破.文章对该矿床矿石稳定同位素地球化学特征进行研究表明:成矿流体主要来源于岩浆岩,围岩(地层)可能只提供了少量成矿物质;该矿床硫的来源单一,属于岩浆硫范畴,矿石与围岩中的硫具有相同的来源;铅的来源以地壳铅为主,并混有少量地幔铅.根据上述研究,结合矿床地质特征及同国内外同类型矿床的对比,认为甲岗雪山多金属矿床是在大陆碰撞后陆内伸展构造背景下,形成于喜马拉雅中期中酸性岩浆活动阶段,矿质主要源自岩浆的石英大脉型钨、钼、铋多金属矿床. 相似文献
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I. V. Chernyshev N. S. Bortnikov A. V. Chugaev G. N. Gamyanin A. G. Bakharev 《Geology of Ore Deposits》2011,53(5):353-373
A collection of galena from the Nezhdaninsky gold deposit (62 samples), as well as galena from the Menkeche silver-base-metal deposit and the Sentyabr occurrence and K-feldspar from intrusive rocks of the Tyry-Dyby ore cluster have been studied using the high-precision (±0.02%) MC-ICP-MS method. Particular ore zones are characterized by relatively narrow variations of isotope ratios (no wider than σ6/4 = 0.26%). Vertical zoning of Pb isotopic composition is not detected. Variation in Pb isotope ratios mainly depends on the type of mineral assemblage. Galena of the gold-sulfide assemblage dominating at the Nezhdaninsky deposit is characterized by the following average isotope ratios: 206Pb/204Pb = 18.472, 207Pb/204Pb = 15.586, and 208Pb/204Pb = 38.605. Galena from the regenerated silver-base-metal assemblage is distinguished by less radiogenic lead isotope ratios: 18.420, 15.575, and 38.518, respectively. In lead from the Nezhdaninsky deposit, the component, whose source is identified as Permian host terrigenous rocks, is predominant. The data points of isotopic composition of lode lead make up a linear trend within the range of μ2 = 9.5-9.6. K-feldspar of granitic rocks has less radiogenic and widely varying lead isotopic composition compared to that of galena. The isotopic data on Pb and Sr constrain the contribution of Late Cretaceous granitic rocks as a source of gold mineralization at the Nezhdaninsky deposit. The matter from the Early Cretaceous fluid-generating magma chamber participated in the ore-forming system of the Nezhdaninsky deposit. The existence of such a chamber is confirmed by the occurrence of Early Cretaceous granitoid intrusions on the flanks of the Nezhdaninsky ore field. The greatest contribution of magmatic lead (～30%) is noted in galena from the silver-base-metal mineral assemblage. This component has isotopic marks characteristic of lower crustal lead: the elevated 208Pb/206Pb ratio relative to the mean crustal value and the lower 207Pb/204Pb ratio. Taken together, they determine a high Th/U ～ 4.0 in the source and μ2 = 9.37–9.50. This conclusion is consistent with the contemporary tectonic model describing evolution of the South Verkhoyansk sector of the Verkhoyansk Foldbelt and the Okhotsk Terrane. 相似文献
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Zhijiao Song Cuihua Chen Yulong Yang Yan Zhang Li Yin Hongzhi Li 《Resource Geology》2020,70(3):273-295
The Nanmushu Zn‐Pb deposit, hosted by the Neoproterozoic Dengying Formation dolostone, is located in the eastern part of the Micangshan tectonic belt at the northern margin of the Yangtze Craton, China. This study involves a systematic field investigation, detailed mineralogical study, and Rb‐Sr and Pb isotopic analyses of the deposit. The results of Rb‐Sr isotopic dating of coexisting sphalerite and galena yield an isochron age of 486.7 ± 3.1 Ma, indicating the deposit was formed during the Late Cambrian to Early Ordovician. This mineralization age is interpreted to be related to the timing of destruction of the paleo‐oil reservoir in the Micangshan tectonic belt. All initial 87Sr/86Sr ratios of sphalerite and galena (0.70955–0.71212) fall into the range of the Mesoproterozoic Huodiya Group basement rocks (0.70877–0.71997) and Dengying Formation sandstone (0.70927–0.71282), which are significantly higher than those of Cambrian Guojiaba Formation limestone (0.70750–0.70980), Cambrian Guojiaba Formation carbonaceous slate (0.70766–0.71012), and Neoproterozoic Dengying Formation dolostone (0.70835–0.70876). Such Sr isotope signatures suggest that the ore strontium was mainly derived from a mixed source, and both of the Huodiya Group basement rocks and Dengying Formation sandstone were involved in ore formation. Both sphalerite and galena are characterized by an upper‐crustal source of lead (206Pb/204Pb = 17.849–18.022, 207Pb/204Pb = 15.604–15.809, and 208Pb/204Pb = 37.735–38.402), and their Pb isotopes are higher than, but partly overlap with, those of the Huodiya Group basement rocks, but differ from those of the Guojiaba and Dengying Formations. This suggests that the lead also originated from a mixed source, and the Huodiya Group basement rocks played a significant role. The Sr and Pb isotopic results suggest that the Huodiya Group basement rocks were one of the most important sources of metallogenic material. The geological and geochemical characteristics show that the Nanmushu Zn‐Pb deposit is similar to typical Mississippi Valley type, and the fluid mixing may be a reasonable metallogenic mechanism for Nanmushu Zn‐Pb deposit. 相似文献
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I. V. Chernyshev A. V. Chugaev N. S. Bortnikov G. N. Gamyanin A. V. Prokopiev 《Geology of Ore Deposits》2018,60(5):398-417
The paper considers the results of high-precision Pb–Pb isotopic analysis of 120 galena samples from 27 Au and Ag deposits of the South Verkhoyansk Synclinorium (SVS) including large Nezhdaninsky deposit (628.8 t Au). The Pb isotopic composition is analyzed on a MC-ICP-MS NEPTUNE mass-spectrometer from solutions with an error of no more than ±0.02% (2σ). Four types of deposits are studied: (i) stratified vein gold–quartz deposits (type 1) hosted in metamorphosed Upper Carboniferous–Lower Permian terrigenous rocks and formed during accretion of the Okhotsk Block to the North Asian Craton synchronously with dislocation metamorphism and related granitic magmatism; (ii) vein gold–quartz (Nezhdaninsky type) deposits also hosted in Lower Permian metasedimentary rocks; (iii) Au–Bi deposits localized at the contact zones of the Late Cretaceous granitic plutons; and (iv) Sn–Ag polymetallic deposits related to granitic and subvolcanic rocks of the Okhotsk Zone of the SVS. The deposits of types 2, 3, and 4 are postaccretionary. The general range of 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios is 18.1516–18.5903 (2.4%), 15.5175–15.6155 (0.63%), and 38.3010–39.0481 (2.0%), respectively. In 206Pb/204Pb–207Pb/204Pb and 206Pb/204Pb–208Pb/204Pb diagrams, the data points of Pb isotopic compositions of all deposits occupy restricted, partly overlapping areas along a general elongated trend. The various SVS Au–Ag deposits can be classified according to the Pb isotopic composition in accordance with all three Pb ratios. Deposits of the same type show distinct Pb isotopic compositions that strongly exceed the scale of analytical error (±0.02%). The differences in Pb isotopic composition within specific deposits are low and subordinate and have little effect on variations in the Pb isotopic composition of the SVS deposits. The μ2 values (Stacey–Kramers model), which characterize the 238U/204Pb ratios of ore lead sources of the SVS deposits, widely vary from 9.7 to 9.38. The ω2 values (232Th/204Pb) are 39.82–36.61, whereas the Th/U ratios are 4.04–3.86. The content of all three radiogenic Pb isotopes and μ2 values of feldspars from SVS intrusive rocks are strongly distinct from those of galena of stratified gold–quartz and vein gold–quartz deposits and are identical to Pb of galena from Au–Bi and Sn–Ag polymetallic deposits, indicating a mostly magmatic origin for the Pb of these deposits. Detailed isotopic study of the Nezhdaninsky deposit shows different Pb isotopic composition of two consecutive mineral assemblages (gold–sulfide and Ag polymetallic): ~0.30, ~0.07, and ~0.22% for 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios, respectively. These differences are interpreted as a result of involvement of at least two metal sources during the evolution of an ore-forming system: (i) host Lower Permian terrigenous rocks and (ii) a magmatic source similar in Pb isotopic composition to that of Sn–Ag polymetallic deposits. The Pb isotopic composition and μ2 and Th/U values show that lead of stratified gold–quartz deposits combines isotopic tracers of lower and upper crustal sources (Upper Carboniferous–Lower Permian terrigenous rocks), lead of which was mobilized by ore-bearing fluids. The high 208Pb/206Pb ratios and Th/U evolutionary parameter are common to all Pb isotopic composition of all studied Au–Ag deposits and SVS Cretaceous intrusive rocks and indicate that Pb sources were depleted in U relative to Th. Taking into account the structure of the region and conceptions on its evolution, we can suggest that the magma source was related to lower crustal subducted rocks of the Archean (~2.6 Ga) North Asian Craton and the Okhotsk terrane. 相似文献
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Bruce R. Doe Peter W. Lipman Carl E. Hedge Hajime Kurasawa 《Contributions to Mineralogy and Petrology》1969,21(2):142-156
Basalts in the Southern Rocky Mountains province have been analyzed to determine if any of them are primitive. Alkali plagioclase xenocrysts armored with calcic plagioclase seem to be the best petrographic indicator of contamination. The next best indicator of contamination is quartz xenocrysts armored with clinopyroxene. On the rocks and the region studied, K2O apparently is the only major element with promise of separating primitive basalt from contaminated basalt inasmuch as it constitutes more than 1 % in all the obviously contaminated basalts. K2O: lead (> 4 ppm) and thorium (> 2 ppm) contents and Rb/Sr (> 0.035) are the most indicative of the trace elements studied. Using these criteria, three basalt samples are primitive (although one contains 1.7% K2O) and are similar in traceelement contents to Hawaiian and Eastern Honshu, Japan, primitive basalts.Contamination causes lead isotope ratios, 206Pb/204Pb and 208Pb/204Pb, to become less radiogenic, but it has little or no effect on 87Sr/86Sr. We interpret the effect on lead isotopes to be due to assimilation either of lower crustal granitic rocks, which contain 5–10 times as much lead as basalt and which have been low in U/Pb and Th/Pb since Precambrian times, or of upper crustal Precambrian or Paleozoic rocks, which have lost much of their radiogenic lead because of heating prior to assimilation. The lack of definite effects on strontium isotopes may be due to the lesser strontium contents of granitic crustal rocks relative to basaltic rocks coupled with lack of a large radiogenic enrichment in the crustal rocks.Lead isotope ratios were found to be less radiogenic in plagioclase separates from an obviously contaminated basalt than in the primitive basalts. The feldspar separate that is rich in sodic plagioclase xenocrysts was found to be similar to the whole-rock composition for 206Pb/204Pb and 208Pb/204Pb whereas a more dense fraction probably enriched in more calcic plagioclase phenocrysts is more similar to the primitive basalts in lead isotope ratios.The primitive basalts have: 206Pb/204Pb 18.09–18.34, 207Pb/204Pb 15.5, 208Pb/204Pb 37.6–37.9, 87Sr/86Sr 0.704–0.705. In the primitive basalts from the Southern Rocky Mountains the values of 206Pb/204Pb are similar to values reported by others for Hawaiian and eastern Honshu basalts and abyssal basalts, whereas 208Pb/204Pb tends to be equal to or a little less radiogenic than those from the oceanic localities. 87Sr/86Sr appears to be equal to or a little greater than those of the oceanic localities. These 206Pb/204Pb and 208Pb/204Pb ratios are distinctly less radiogenic and 87Sr/86Sr values are about equal to those reported by others for volcanic islands on oceanic ridges and rises.Publication authorized by the Director, U.S. Geological Survey 相似文献
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The Lovozero alkaline massif—an agpaitic nepheline syenite layered intrusion—is located in the central part of the Kola Peninsula, Russia, and belongs to the Kola ultramafic alkaline and carbonatitic province (KACP) of Devonian age. Associated loparite and eudialyte deposits, which contain immense resources of REE, Nb, Ta, and Zr, constitute a world class mineral district. Previous Sr, Nd, and Hf isotope investigations demonstrated that these rocks and mineral deposits were derived from a depleted mantle source. However, because the Sr, Nd, and Hf abundances in the Kola alkaline rocks are significantly elevated, their isotopic compositions were relatively insensitive to contamination by the underlying crustal rocks through which the intruding magmas passed. Pb occurring in relatively lower abundance in the KACP rocks, by contrast, would have been a more sensitive indicator of an acquired crustal component. Here, we investigate the lead isotopic signature of representative types of Lovozero rocks in order to further characterize their sources. The measured Pb isotopic composition was corrected using the determined U and Th concentrations to the age of the crystallization of the intrusion (376?±?28 Ma, based on a 206Pb/204Pb versus 238U/204Pb isochron and 373?±?9 Ma, from a 208Pb/204Pb versus 232Th/204Pb isochron). Unlike the previously investigated Sr, Nd, and Hf isotopes, the lead isotopic composition plot was well outside the FOZO field. The 206Pb/204Pb values fall within the depleted MORB field, with some rocks having lower 207Pb/204Pb but higher 208Pb/204Pb values. Together with other related carbonatites having both lower and higher 206Pb/204Pb values, the combined KACP rocks form an extended linear array defining either a?~2.5-Ga secondary isochron or a mixing line. The projection of this isotopic array toward the very unradiogenic composition of underlying 2.4–2.5-Ga basaltic rocks of the Matachewan superplume and associated Archean granulite facies country rock provides strong evidence that this old lower crust was the contaminant responsible for the deviation of the Lovozero rocks from a presumed original FOZO lead isotopic composition. Evaluating the presence of such a lower crustal component in the Lovozero rock samples suggests a 5–10% contamination by such rocks. Contamination by upper crustal rock is limited to only a negligible amount. 相似文献
16.
H-O-S-Cu-Pb Isotopic Constraints on the Origin of the Nage Cu-Pb Deposit, Southeast Guizhou Province, SW China 总被引：1，自引：0，他引：1
The Nage Cu-Pb deposit,a new found ore deposit in the southeast Guizhou province,southwest China,is located on the southwestern margin of the Jiangnan Orogenic Belt.Ore bodies are hosted in slate and phyllite of Neoproterozoic Jialu and Wuye Formations,and are structurally controlled by EW-trending fault.It contains Cu and Pb metals about 0.12 million tonnes with grades of 0.2 wt% to 3.4 wt% Cu and 1.1 wt% to 9.27 wt% Pb.Massive and disseminated Cu-Pb ores from the Nage deposit occur as either veinlets or disseminations in silicified rocks.The ore minerals include chalcopyrite,galena and pyrite,and gangue minerals are quartz,sericite and chlorite.The H-O isotopic compositions of quartz,S-Cu-Pb isotopic compositions of sulfide minerals,Pb isotopic compositions of whole rocks and ores have been analyzed to trace the sources of ore-forming fluids and metals for the Nage Cu-Pb deposit.The δ65CuNBS values of chalcopyrite range from-0.09% to +0.33‰,similar to basic igneous rocks and chalcopyrite from magmatic deposits.δ65CuNBS values of chalcopyrite from the early,middle and final mineralization stages show an increasing trend due to63Cu prior migrated in gas phase when fluids exsolution from magma.δ34SCDT values of sulfide minerals range from 2.7‰ to +2.8‰,similar to mantle-derived sulfur(0±3‰).The positive correlation between δ65CuNBS and δ34SCDT values of chalcopyrite indicates that a common source of copper metal and sulfur from magma.δDH2OSMOW and δ18OH2O-SMOW values of water in fluid inclusions of quartz range from 60.7‰ to 44.4‰ and +7.9‰ to +9.0‰(T=260°C),respectively and fall in the field for magmatic and metamorphic waters,implicating that mixed sources for H2O in hydrothermal fluids.Ores and sulfide minerals have a small range of Pb isotopic compositions(208Pb/204Pb=38.152 to 38.384,207Pb/204Pb=15.656 to 17.708 and 206Pb/204Pb=17.991 to 18.049) that are close to orogenic belt and upper crust Pb evolution curve,and similar to Neoproterozoic host rocks(208Pb/204Pb=38.201 to 38.6373,207Pb/204Pb=15.648 to 15.673 and 206Pb/204Pb=17.820 to 18.258),but higher than diabase(208Pb/204Pb=37.830 to 38.012,207Pb/204Pb=15.620 to 15.635 and206Pb/204Pb=17.808 to 17.902).These results imply that the Pb metal originated mainly from host rocks.The H-O-S-Cu-Pb isotopes tegather with geology,indicating that the ore genesis of the Nage Cu-Pb deposit is post-magmatic hydrothermal type. 相似文献
17.
A. V. Chugaev O. Yu. Plotinskaya I. V. Chernyshev A. A. Kotov 《Doklady Earth Sciences》2014,457(1):887-892
Using the high-precision technique of MC-ICP mass spectrometry, the isotope composition of lead was studied for the first time in sulfides of different mineral associations at the Verninskoe deposit that belong to large gold deposits of the Lena Province. In 23 monofractions of sulfides (pyrite, arsenopyrite, galena, and sphalerite), the Pb-Pb data showed a pronounced heterogeneity of the isotope composition of ore lead (206Pb/204Pb = 18.21–18.69, 207Pb/204Pb = 15.59–15.67, and 208Pb/204Pb = 37.98–38.63) for the deposit as a whole. This heterogeneity is also seen to a lesser degree within individual samples. In this case, a correlation takes place between the isotope composition of ore Pb and the type of mineral association: the sulfides in earlier associations are characterized by lower contents of the 206Pb, 207Pb, and 208Pb radiogenic isotopes compared to the minerals of later parageneses. The comparison of Pb-Pb isotope characteristics of ore mineralization of the Verninskoe deposit to those of the Sukhoi Log deposit (the greatest in the Lena Province) testifies to the geochemical similarity of the sources of ore Pb involved in the formation of these deposits. The sources as such were terrigenous rocks of the Bodaibo synclinorium formed mainly as a result of the disintegration of Precambrian rocks of the Siberian craton. 相似文献
18.
《International Geology Review》2012,54(3):337-349
The Dexing ore deposit, Jiangxi Province, is the largest porphyry copper deposit in China. Controversies exist regarding the ore-forming source of this deposit. We have conducted Pb isotope analyses of pyrites from the Tongchang and Fujiawu mines. Our results document consistent Pb isotopes from these two orebodies, with 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of 17.954–18.320, 15.407–15.517, and 37.888–38.153, respectively. These Pb isotope ratios are consistent with those of ore-bearing adakitic porphyries but distinctly different from those of the Neoproterozoic metamorphic wall rocks, which indicates that the metals were derived from the porphyries. Based on previous S and Os isotopic data and comparisons with more than 20 Mo-bearing deposits worldwide, we further attribute the narrow range of δ34S values of sulphide minerals and high Re–187Os concentrations of associated molybdenites to a mantle origin. This large-scale copper deposit was evidently emplaced in a continental arc setting attending westward subduction of the palaeo-Pacific plate. Partial melting of the downgoing oceanic slab generated the adakitic magmas. The associated metals were extracted from the lithospheric mantle by these magmas during ascent through the mantle wedge. 相似文献
19.
Neng‐Ping Shen Jian‐Tang Peng Rui‐Zhong Hu Shen Liu Ian M. Coulson 《Resource Geology》2011,61(1):52-62
The Xujiashan antimony deposit is hosted by marine carbonates of the Upper Sinian Doushantuo and Dengying Formations in Hubei Province, South China. Our Sr isotopic data from pre‐ and syn‐mineralization calcites that host the mineralization show that the pre‐mineralization calcite displays a narrow range of 87Sr/86Sr ratios (0.7096 to 0.7097), similar to the ratios of the Sinian seawater, and high Sr concentrations (2645 to 8174 ppm). In contrast, the syn‐mineralization calcite exhibits low Sr concentrations (785 to 2563 ppm) and high 87Sr/86Sr ratios (0.7109 to 0.7154), which is interpreted as the result of addition of radiogenic strontium during the antimony mineralization. The study of Sr isotopes suggests that their Sr component to the pre‐mineralization calcite derived directly from the host rocks (i.e. the Sinian marine carbonates), while radiogenic 87Sr for the syn‐mineralization calcite derived from the underlying Mesoproterozoic Lengjiaxi Group basement through hydrothermal fluid circulation along the major fault that hosts the mineralization. The Pb isotopic ratios of stibnite are subdivided into two groups (Group A and Group B), Group A is characterized by higher radiogenic lead, with 206Pb/204Pb = 18.874 to 19.288, 207Pb/204Pb = 15.708 to 15.805, and 208Pb/204Pb = 38.642 to 39.001. Group B shows lower lead isotope ratios (206Pb/204Pb = 17.882 to 18.171, 207Pb/204Pb = 15.555 to 15.686, and 208Pb/204Pb = 37.950 to 38.340). The single‐stage model ages of Group A are mainly negative or slightly positive values (‐258 to 3 Ma), while those of Group B range from 636 to 392 Ma, with an average of 495 ± 65 Ma. In addition, there are positive linear correlations among Pb isotopic ratios. These results suggest that the lead of Group A stibnite was mainly derived from the Sinian marine carbonates, and that of Group B stibnite from the underlying Lengjiaxi Group basement. This conclusion is consistent with the results of the Sr isotopes. These results indicate that the Xujiashan deposit is not syngenetic sedimentary and in situ reworked origin as previously considered. The metal (mainly Sb) of this deposit was not only derived from the Sinian host rocks, but also partly derived from the underlying Mesoproterozoic Lengjiaxi Group basement. 相似文献