Re-Os Dating of Chalcopyrite from the Lala IOCG Deposit in the Kangdian Copper Belt,China

This study focused on the typical Precambrian copper- iron-gold-uranium deposits in the southwestern margin of the Yangtze block, such as the Lala in Huili, Dahongshan in Xinping, Yinachang in Wuding, and Chahe in Yuanjiang. Through systematically sampling of rocks, mineral and single mineral samples, this study discussed the continental geodynamics, age of magmatic rocks and metallogenic epoch, coupling relationship between polymetallic elements and ore-forming fluid, and the coupling relationship between magma evolution and polymetallic mineralization based on the latest metallogenic theory and modern analytical techniques.

Metallogenic Age and Ore-forming Material Sources of the Dahongshan Fe-Cu Deposit,Yunnan Province:Insights from Molybdenite Re-Os Dating and H-O-S-Pb Isotopes

The Dahongshan Fe-Cu(-Au)deposit is a superlarge deposit in the Kangdian metallogenic belt,southwestern China,comprising approximately 458 Mt of Fe ores(40%Fe)and 1.35 Mt Cu.Two main types of Fe-Cu(-Au)mineralization are present in the Dahongshan deposit:(1)early submarine volcanic exhalation and sedimentary mineralization characterized by strata-bound fine-grained magnetite and banded Fe-Cu sulfide(pyrite and chalcopyrite)hosted in the Na-rich metavolcanic rocks;(2)late hydrothermal(-vein)type mineralization characterized by Fe-Cu sulfide veins in the hosted strata or massive coarse-grained magnetite orebodies controlled by faults.While previous studies have focused primarily on the early submarine volcanic and sedimentary mineralization of the deposit,data related to late hydrothermal mineralization is lacking.In order to establish the metallogenic age and ore-forming material source of the late hydrothermal(-vein)type mineralization,this paper reports the Re-Os dating of molybdenite from the late hydrothermal vein Fe-Cu orebody and H,O,S,and Pb isotopic compositions of the hydrothermal quartz-sulfide veins.The primary aim of this study was to establish the metallogenic age and ore-forming material source of the hydrothermal type orebody.Results show that the molybdenite separated from quartz-sulfide veins has a Re-Os isochron age of 831±11 Ma,indicating that the Dahongshan Fe-Cu deposit experienced hydrothermal superimposed mineralization in Neoproterozoic.The molybdenite has a Re concentration of 99.7-382.4 ppm,indicating that the Re of the hydrothermal vein ores were primarily derived from the mantle.The δ^(34)S values of sulfides from the hydrothermal ores are 2‰-8‰ showing multi-peak tower distribution,suggesting that S in the ore-forming period was primarily derived from magma and partially from calcareous sedimentary rock.Furthermore,the abundance of radioactive Pb increased significantly from ore-bearing strata to layered and hydrothermal vein ores,which may be related to the later hydrothermal transformation.The composition of H and O isotopes within the hydrothermal quartz indicates that the ore-forming fluid is a mixture of magmatic water and a small quantity of water.These results further indicate that the late hydrothermal orebodies were formed by the Neoproterozoic magmatic hydrothermal event,which might be related to the breakup of the Rodinia supercontinent.Mantle derived magmatic hydrothermal fluid extracted ore-forming materials from the metavolcanic rocks of Dahongshan Group and formed the hydrothermal(-vein)type Fe-Cu orebodies by filling and metasomatism.

Re-Os Isotopic Age of Molybdenite of the Jingren Deposit and its Mineralogical Significance of Magnetite,Pyrite and Chalcopyrite

The Jingren deposit is part of the Qimantage metallogenic belt within the eastern Kunlun orogenic belt,the largest metallogenic belt in Qinghai Province,northwestern China.Exploration data show that the metal resources of the Jingren deposit are greater than 93000 t in a mining area of 76.15 km2,which indicates significant exploration potential in the near future.Three W–E-trending faults,F1-3,dominate the extension of the mineralization zone,which consists of chalcopyrite,pyrite,magnetite,galena,sphalerite,and molybdenite as well as bismuth-bearing minerals.The deposit contains a large amount of late Triassic intrusive rocks,however,previous research did not reach a consensus on the timing or the origin of the mineralization owing to a lack of geochronological data and poor exposure conditions.In the present study,Re-Os isotopic dating from six molybdenite samples collected from a borehole of the granodiorite in the Jingren deposit using negative thermal ionization mass spectrometry(NTIMS)showed 187 Re and 187 Os concentrations of 0.26–4.40 ppm and 1.03–16.46 ppb,respectively,with an initial 187 Os/188 Os value of 0.06±0.19.This proves that the Jingren deposit has a metallogenic age of(225±4)Ma and is the product of united mineralization of the Qimantage metallogenic belt and that the Jingren deposit might actually be an Indosinian metallogeny.In addition,the Re content of these samples,at 0.42 ppm to 7.00 ppm shows that the mineralization was derived mainly from a crustal source.Furthermore,electron probe microanalysis(EPMA)conducted on chalcopyrite obtained from 22 metallic mineral samples revealed(Fe+Cu)/S ratios of 1.801–1.947 with an average of 1.852,which is lower than the ideal value(1.875).Besides,the main ore body formed in a relatively higher temperature environment than the surrounding rocks in the Jingren deposit.These data indicate that the Jingren deposit formed in a metallogenic environment at lower temperature.Moreover,according to the TiO_(2)-Al_(2)O_(3)-(MgO+MnO)and TiO_(2)-Al_(2)O_(3)-MgO genetic classification diagram for magnetite,the Jingren deposit most likely belongs to the skarn family.In addition,the Co-Ni-As genetic classification diagram of the pyrite indicates sedimentary and skarn genetic characteristics.

Re-Os Dating of Molybdenite from the Nannihu Mo (-W) Orefield in the East Qinling and Its Geodynamic Significance

Located in the East Qinling molybdenum metallogenic belt on the southern margin of the North China craton, the Nannihu Mo (-W) orefield comprising Nannihu, Sandaozhuang, and Shangfanggou deposits is a superlarge skarn-porphyry Mo (-W) orefield in the world. Re-Os dating was performed of six molybdenite samples from the Mo deposits in the Nannihu Mo orefield with inductively coupled plasma mass spectrometry (ICP-MS). The results show that the Re-Os model ages are 145.8±2.1-141.8±2.1 Ma for the Nannihu deposit, 145.4±2.0-144.5±2.2 Ma (averaging 145.0±2.2 Ma) for the Sandaozhuang deposit and 145.8±2.1-143.8±2.1 Ma (averaging 144.8±2.1 Ma) for the Shangfanggou deposit; dating of the six samples yields an isochron age of 141.5±7.8 Ma (2σ), which accurately determines the timing of mineralization. The results also suggest that the ore-forming materials were mainly derived from the lower crust, mixed with minor mantle components. These Mo deposits were formed during the transition of the Mesozoic tectonic regime in eastern China, and its mineralization was a part of the Late Mesozoic large-scale mineralization in that region.

Re-Os Dating of the Pulang Porphyry Copper Deposit in Zhongdian,NW Yunnan, and Its Geological Significance

The Pulang porphyry copper deposit is located in the Zhongdian island arc belt, NW Yunnan, in the central part of the Sanjiang area, SW China, belonging to the southern segment of the Yidun island arc belt on the western margin of the Yangtze Platform. In the Yidun island arc, there occur well-known 'Gacun-style' massive sulfide deposits in the northern segment and plenty of porphyry copper deposits in the southern segment, of which the Pulang porphyry copper deposit is one of the representatives. Like the Yulong porphyry copper deposit, this porphyry copper deposit is also one of the most important porphyry copper deposits in the eastern Qinghai-Tibet Plateau. But it is different from other porphyry copper deposits in the eastern Qinghai-Tibet Plateau (e.g. those in the Gangdise porphyry copper belt and Yulong porphyry copper belt) in that it formed in the Indosinian period, while others in the Himalayan period. Because of its particularity among the porphyry copper deposits of China, this porphyry copper deposit is of great significance for the study of the basic geology and the evaluation and prediction of mineral resources in the Zhongdian island arc belt. However, no accurate chronological data are available for determining the timing of mineralization of the porphyry copper deposit. By field observation in the study area and Re-Os dating of molybdenite and K-Ar dating of hydrothermal minerals and whole rock from the typical geological bodies, the timing of mineralization of the porphyry copper deposit has systematically been determined for the first time. The K-Ar age for the hydrothermal mineralization of biotite-quartz monzonitic porphyry that has undergone patassic silicate (biotite and K-feldspar) alteration ranges from 235.4±2.4 to 221.5±2.0 Ma and the Re-Os age for molybdenite in the quartz-molybdenite stage is ~213±3.8 Ma. These data are very close to each other, suggesting that the ore-forming processes of the Pulang porphyry copper deposit was completed in the Indosinian. But the K-feldspar K-Ar age of the main orebodies suggests that the hydrothermal activity related to porphyry copper mineralization continued till ~182.5±1.8 Ma. This indicates that the lifespan of the hydrothermal system related to porphyry copper mineralization may have lasted at least 40 Ma. This hydrothermal thermal system with such a long lifespan may be one of the necessary conditions for forming large porphyry copper deposits with a high grade. No late Yanshanian and/or Himalayan magmatism (mineralization) were superimposed in the Pulang porphyry copper deposit.

LA-ICP-MS Zircon U-Pb Dating of Intermediate-Acidic Intrusive Rocks and Molybdenite Re-Os Dating from the Bangpu Mo (Cu) Deposit, Tibet and its Geological Implication

The multi-stage intrusions of intermediate-acid magma occur in the Bangpu mining district, the petrogenic ages of which have been identified. The times and sequences of their emplacement have been collated and stipulated in detail in this paper by using the laser ablation-inductively coupled plasma-mass spectrometry （LA-ICP-MS） zircon U-Pb dating method. The ages of biotite monzogranite that were formed before mineralization in the southwest of this mining district are 70±1 Ma （mean square of weighted deviates （MSWD） =9.5, n=8） and 60.60±0.31 Ma （MSWD=3.8, n=16）, which belong to the late Cretaceous-early Paleocene in age. That means, they are products of an early tectonicmagmatic event of the collision between the Indian and Asian continentals. The ages of ore-bearing monzogranite porphyry and ore-bearing diorite porphyrite are 16.23±0.19 Ma （MSWD=2.0, n=26） and 15.16±0.09 Ma （MSWD=3.9, n=5） separately, which belong to the middle Miocene in age; namely, they are products of the Gangdese post-collision extensional stage when crust-mantle materials melted and mixed as well as magmatic intrusion simultaneously occurred. Some zircons with ages of 203.6±2.2 Ma （MSWD=1.18, n=7） were captured in the ore-bearing diorite porphyrite, which shows that there had been tectono-magmatic events in the late Triassic-early Jurassic. Molybdenum （copper） ore-bodies produced in the monzogranite porphyry and copper （molybdenum） ore-bodies produced in the diorite porphyrite are the main ore types in this ore deposit. The model ages of Re-Os isotopic dating for the 11 molybdenite are 13.97-15.84 Ma, while isochron ages are 14.09±0.49 Ma （MSWD=26）. The isochron ages of seven molybdenite from molybdenum （copper） ore with monzogranite porphyry type are 14.11±0.31 Ma （MSWD=5.2）. There is great error in the isochron ages of four molybdenite from copper （molybdenum） ore with diorite porphyrite type, and their weighted average model ages of 14.6±1.2 Ma （MSWD=41）, which generally represent the mineralization age. The results about the Re-Os isotopic dating of molybdenite in the ore of different types have limited exactly that, the minerlazation age of this ore deposits is about 14.09 Ma, which belongs to the middle Miocene mineralization. The Bangpu deposit has a uniform metallogenic dynamics background with the porphyry type and skarn-type deposits such as Jiama, Qulong and others.

LA-ICP-MS Zircon U-Pb Geochronology of the Fine-grained Granite and Molybdenite Re-Os Dating in the Wurinitu Molybdenum Deposit,Inner Mongolia,China

The Wurinitu molybdenum deposit,located in Honggor,Sonid Left Banner of Inner Mongolia,China,is recently discovered and is considered to be associated with a concealed fine-grained granite impregnated with molybdenite.The wall rocks are composed of Variscan porphyritic-like biotite granite and the Lower Ordovician Wubin'aobao Formation.LA-ICP-MS zircon U-Pb dating of the fine-grained granite reveals two stages of zircons,one were formed at 181.7±7.4 Ma and the other at 133.6±3.3 Ma.The latter age is believed to be the formation age of the fine-grained granite,while the former may reflect the age of inherited zircons,based on the morphological study of the zircon and regional geological setting.The Re-Os model age of molybdenite is 142.2±2.5 Ma,which is older than the diagenetic age of the fine-grained granite.Therefore the authors believe that the metallogenic age of the Wurinitu molybdenum deposit should be nearly 133.6±3.3 Ma or slightly later,i.e.,Early Cretaceous.Combined with regional geological background research,it is speculated that the molybdenum deposits were formed at the late Yanshanian orogenic cycle in the Hingganling-Mongolian orogenic belt,belonging to the relaxation epoch posterior to the compression and was associated with the closure of the Mongolia-Okhotsk Sea.

Re-Os Isotopic Dating of a W-Be Polymetallic Deposit in the Southern Qinling Region, China

Objective In recent years, a series of tungsten prospecting breakthroughs have been made in the southern Qinling Mountains. Especially, a new deposit type with a scheelite -beryl-molybdenite assemblage in the Zhen＇an area of Shaanxi Province was firstly discovered. This deposit is currently in a detailed investigation stage, and no detailed study has been yet conducted. This work selected one molybdenite sample from the Be （W） ores in this deposit for Re-Os isotope measurements to define the time limit of tungsten and beryllium mineralization, and to further reveal the ore-forming geological setting of rare metals in the southern Qinling region.

Rb-Sr Dating of Pyrite and Quartz Fluid Inclusions and Origin of Ore-forming Materials of the Jinshan Gold Deposit, Northeast Jiangxi Province, South China

The Jinshan gold deposit is located in the Northeast Jiangxi province,South China,which related to the ductile shear zone.It contains two ore types,i.e.the alteration-type ore and the goldbearing quartz vein ore.Rb-Sr age dating is applied to both gold-bearing pyrite in the alteration-type ore and fluid inclusion in the gold-bearing quartz vein to make clear the time of the gold mineralization of the Jinshan deposit.Analytical results of this study yielded that the age of the alteration-type ore bodies is about 838±110Ma,with an initial 87Sr/86Sr value of 0.7045±0.0020.However,the age of the gold-bearing quartz vein-type ore is about 379±49Ma,and the initial 87Sr/86Sr is 0.7138±0.0011.Based on the age data from this work and many previous studies,the authors consider that the Jinshan gold deposit is a product of multi-staged mineralization,which may include the Jinninian,Caledonian,Hercynian,and Yanshanian Periods.Among them,the Jinninian Period and the Hercynian Period might be the two most important ore-forming periods for Jinshan deposit.The Jinninian Period is the main stage for the formation of alteration-type ore bodies,while the Hercynian Period is the major time for ore bodies of gold-bearing quartz vein type.The initial values of the 87Sr/86Sr from this study,as well as the previous isotope and trace element studies,indicate that the ore-forming materials mainly derived from the metamorphic wall rocks,and the ore-forming fluids mainly originated from the deep metamorphic water.

Direct Re–Os dating of pyrite from the Jianchaling Au deposit,West Qinling,China

The West Qingling Orogen is endowed with more than 1100 t gold resources and with 50 gold deposits,ranking it the third-largest gold province in China.The Jianchaling giant gold deposit with 52 t gold reserve is a typical orogenic gold deposit in West Qinling Orogen.The deposit lacks accurate and direct metallogenic age.Five pyrite samples collected from the quartz-polymetallic veins yielded Re–Os isochron age of 206.3±2.7 Ma and an initial187 Os/188 Os ratio of 0.1154±0.0016(MSWD=0.54).The pyrites were analyzed by the electron microprobe(EMPA),and the results show that the iron content ranges from 45.1 to 47.8 wt.%,the sulfur content ranges from 52.0 to 53.5 wt.%,and the gold content varies from0.022 to 0.035%.The higher gold content means that gold is closely related to pyrite,which is a gold-bearing mineral.Moreover,the age is very close to the previous fuchsite40 Ar/39 Ar isotopic ages of 199–194 Ma,which indicates that the gold mineralization at Jianchaling has begun in the Late Triassic(206 Ma),and continued into the Early Jurassic.Through summary and comparison,it is found that the gold metallogenic age of the southern ore belt of the Mian-Lue Suture belt in the West Qinling is younger than that of the northern ore belt,suggesting that the gold deposits in the southern ore belt such as Jianchaling were formed in the transitional period from oceanic subduction to continental collision.

Molybdenite Re-Os,titanite and garnet U-Pb dating of the Magushan skarn Cu-Mo deposit,Xuancheng district,Middle-Lower Yangtze River Metallogenic Belt

The Magushan skarn Cu-Mo deposit is a representative example of the skarn mineralization occurring within the Xuancheng ore district of the Middle-Lower Yangtze River Metallogenic Belt of eastern China.The precise age of an ore deposit is important for understanding the timing of mineralization relative to other geological events in a region and to fully place the formation of a mineral deposit within the geological context of other processes that occur within the study area.Here,we present new molybdenite Re-Os and titanite and andradite garnet U-Pb ages for the Magushan deposit and use these data to outline possible approaches for identifying genetic relationships in geologically complex areas.The spatial and paragenetic relationships between the intrusions,alteration,and mineralization within the study area indicates that the formation of the Magushan deposit is genetically associated with the porphyritic granodiorite.However,this is not always the case,as some areas contain complexly zoned plutons with multiple phases of intrusion or mineralization may be distal from or may not have any clear spatial relationship to a pluton.This means that it may not be possible to determine whether the mineralization formed as a result of single or multiple magmatic/hydrothermal events.As such,the approaches presented in this study provide an approach that allows the identification of any geochronological relationships between mineralization and intrusive events in areas more complex than the study area.Previously published zircon U-Pb data for the mineralization-related porphyritic granodiorite in this area yielded an age of 134.2±1.2 Ma(MSWD=1.4)whereas the Re-Os dating of molybdenite from the study area yielded an isochron age of 137.7±2.5 Ma(MSWD=0.43).The timing of the mineralizing event in the study area was further examined by the dating of magmatic accessory titanite and skarn-related andradite garnet,yielding U-Pb ages of 136.3±2.5 Ma(MSWD=3.2)and 135.9±2.7 Ma(MSWD=2.5),respectively.The dating of magmatic and hydrothermal activity within the Magushan area yields ages around 136 Ma,strongly suggesting that the mineralization in this area formed as a result of the emplacement of the intrusion.The dates presented in this study also provide the first indication of the timing of mineralization within the Xuancheng district.providing evidence of a close genetic relationship between the formation of the mineralization within the Xuancheng district and the Early Cretaceous magmatism that occurred in this area.This in turn suggests that other Early Cretaceous intrusive rocks within this region are likely to be associated with mineralization and should be considered highly prospective for future mineral exploration.This study also indicates that the dating of garnet and titanite can also provide reliable geochronological data and evidence of the timing of mineralization and magmatism,respectively,in areas lacking other dateable minerals(e.g.,molybdenite)or where the relationship between mineralization and magmatism is unclear,for example in areas with multiple stages of magmatism,with complexly zoned plutons,and with distal skarn mineralization.

Early Silurian Wuchuan–Sihui–Shaoguan exhalative sedimentary pyrite belt, South China: constraints from zircon dating for K-bentonite of the giant Dajiangping deposit

The Wuchuan-Sihui-Shaoguan(WSS)exhalative sedimentary pyrite belt in the southwestern part of the Qinzhou-Hangzhou(Qin-Hang)belt is the most important sulfur industry base in China.However,a wide range of metallogenetic ages spanning from Ediacaran to Devonian has been reported in the literature.This age range does not support the idea that the typical character of"coeval mineralization"in an exhalative sedimentary mineralization belt in China and worldwide.Therefore,the precise determination of mineralization ages of representative deposits is necessary to provide guides for exploration and metallogenetic models.The Dajiangping pyrite deposit is a typical example of this kind of deposits and is also the largest deposit with a proven reserve of 210 Mt.This deposit was thought to have formed in Ediacaran or Devonian.In this study,2-3 layers of 10-25 cm thick 2M1-type microcrystalline muscovite slate abruptly embedded in the No.Ⅳmassive orebody of the deposit has been identified to be low-grade metamorphic K-bentonite.A Concordia zircon LA-ICP-MS U-Pb age of 432.5±1.3 Ma(mean standard weighted deviation of concordance and equivalence=1.2;N=11)has been yielded for the low-grade metamorphic K-bentonite.This age is distinctly different from the Rb-Sr isochron age of630.1±7.3 Ma for siliceous rock at the top of the No.Ⅲbanded orebody and the Re-Os isochron age of 389±62 Ma for pyrites from a laminated orebody.Instead,it is close to the intercept age(429 Ma)of the youngest detrital zircons from sandstone interlayers of the No.Ⅲbanded orebody.The Concordia age is also coincident with those of the Late Caledonian(400-460 Ma)magmatism-metamorphism events which are widely distributed in Cathaysia Block.Particularly,it agrees well with that of the Early Silurian extensional volcanism(434-444 Ma)which have been revealed in the Dabaoshan,Siqian-Hekou,and Nanjing volcanic basins in northern Guangdong Province and southern Jiangxi Province.Hence,the dating result in this study confirms that the sedimentary time of the ore-host Daganshan Formation is Early Silurian,and implies that the mineralization age of the Dajiangping pyrite deposit should also be Early Silurian.In combination with the Early Silurian age of Shezui pyrite deposit and the Dabaoshan volcanic basin along the WSS pyrite belt,it could be inferred that the WSS pyrite belt provides a record of the northern expanding of Qinzhou-Fangcheng trough in Early Silurian and that the exhalative pyrite mineralization was triggered by the postcollisional extension of the margin of Cathaysia Block after the intracontinental collision between Cathaysia Block and Yangtze Block during Late Caledonian stage.

Geological Characteristics and Molybdenite Re-Os Isotopic Dating of Shiyaogou Porphyry Molybdenum Deposit,Western Henan Province

The Shiyaogou deposit,located in Songxian,Henan Province,China,is a medium-sized Molybdenum deposit newly discovered in the East Qinling molybdenum belt.Occurring in the altered Proterozoic Xionger Group,mineralization of the deposit consists of molybedenite disseminations and quartz -molybdenite veinlets and stockworks.Hydrothermal alteration is well developed and is composed of potassic alteration,silicification,sericitization,pyriti-

青海格尔木驼路沟喷流沉积型钴(金)矿床的黄铁矿Re-Os定年

青海驼路沟矿床是新近发现的中国西北首例独立大型喷流沉积型钴（金）矿床，赋矿岩石为富钠的热水沉积岩——石英钠长石岩。利用Re-Os同位素体系（ICP-MS方法）对不同类型矿石中的7件黄铁矿样品进行了定年，结果表明尽管它们的Re（0．122×10^-9～8．988×10^-9）和Os（0．00313×10^-9～0．05366×10^-9）的含量很低，但在两种相关图解上分别得到432±23Ma和442±17Ma较好等时线年龄。该Re-Os定年结果不仅进一步厘定区域纳赤台群地层的主体时代为早古生代，而且为确定东昆仑造山带晚奥陶世板块裂解及成矿作用提供了新的重要证据，对深入认识区域成矿规律和探讨地质构造演化具重要意义。

安徽铜陵新桥Cu-Au-Fe-S矿床黄铁矿Re-Os定年及成矿意义

安徽铜陵地区是长江中下游Cu-Au-Fe-S成矿带中的一个重要成矿区，新桥大型Cu-Au-Fe-S矿床为其重要的矿床之一。运用Re-Os同位素定年方法对该矿床中矿石的黄铁矿进行了精确定年测定，首次获得了黄铁矿的Re-Os等时线年龄为126±11Ma，初始Os值1.2±1.9（MSWD=2.6），属早白垩世，代表了铁硫化物的成矿年龄。结合前人的精确同位素定年结果，认为铜陵地区存在两种成矿事件，一种是与Cu-Au-Mo矿有关的成矿事件，代表的铜钼金硫化物的成矿年龄为138.0～140.0Ma；另一种与铁矿有关的成矿事件，代表的铁硫化物的成矿年龄为112.6～126Ma。

辽东裂谷白云金矿载金黄铁矿Re-Os定年及其地质意义

白云金矿是辽东裂谷区内重要的大型金矿之一,长期以来缺少直接的年代学数据。本次对白云金矿不同矿石类型中的8件载金黄铁矿进行了Re-Os同位素定年,获得其等时线年龄为225.3±7.0 Ma(MSWD=5.8),187Os/188Os初始值为2.1±2.8。结合前人的研究成果及本次年代学研究得出:白云金矿形成于印支期,其成矿物质主要为壳源,白云金矿是与印支期岩浆活动有关的热液矿床;其形成构造背景可能为受蒙古–鄂霍次克大洋向南北两侧俯冲之后的陆内后碰撞造山环境。本次研究也为今后在辽东裂谷区寻找与印支期岩浆活动有关的矿床提供了依据。

湘中龙山大型金锑矿床成矿时代研究--黄铁矿Re-Os和锆石U-Th／He定年

龙山金锑矿床是湘中锑-金矿集区最重要的矿床之一，因缺少适合传统放射性同位素定年的矿物，其成矿时代以往未得到很好的限定，制约了对矿床成因的认识。由于分析测试技术的进步，Re-Os同位素定年技术得到了发展，可对热液矿床中形成的低Re、Os含量的硫化物进行较准确可靠的年龄测定，从而可为低温热液矿床的形成时代提供有效制约。锆石u．Th／He同位素定年，也是近年发展和成熟起来的定年技术，对低温热事件极其敏感，同样是约束低温成矿年龄的重要手段之一。本文采用矿床中黄铁矿Re-Os同位素和蚀变围岩中受成矿热事件影响的锆石U—Th／He同位素定年技术，对龙山金锑矿床的成矿时代进行了研究。定年结果显示：热液成因黄铁矿的Re-Os等时线年龄为195±36Ma，对应于印支晚期；锆石U-Th／He年龄为51．2～133．3Ma，经Ft校正后，U—Th／He年龄分布于93．78—258．29Ma之间，平均值为160．7±7．3Ma，对应于燕山早期。该矿床可能发生了200Ma和160Ma的两次成矿作用；或者矿床形成于200Ma左右，但是受到了160Ma左右岩浆热事件的改造，黄铁矿Re-Os年龄代表成矿年龄，而锆石U—Th／He年龄则代表第二期热事件发生的时间。无论是200Ma左右一次成矿，还是另有160Ma左右的成矿作用叠加，这两个年龄分别与区内两期岩浆活动的时间相当，这表明岩浆事件对驱动矿床的形成发挥了重要的作用。

贵州贞丰烂泥沟卡林型金矿床含砷黄铁矿Re-Os同位素测年及地质意义

贵州贞丰烂泥沟金矿(现称锦丰金矿)是滇黔桂“金三角”已知最大的卡林型金矿床,矿体赋存于断层破碎带内,最主要的载金矿物是具环带结构的含砷黄铁矿。本文运用Re-Os同位素法对该矿床的9个含砷黄铁矿样品进行了两次测试,成功获得10-9～10-12级Re-Os同位素数据:Re0.1257～1.233ng/g,Os6.75～33.50pg/g,等时线年龄为193±13Ma,反映其成矿时代为早侏罗世。等时线的初始n(187Os)/n(188Os)值为1.127±0.043,指示成矿物质来源于地壳而不是地幔。结合其他资料,初步建立其成矿模式为:盆地流体不断地从沉积物中萃取出包括金在内的成矿组分,形成含矿流体。印支期挤压造山期间,含矿流体沿不整合接触面和同生断层向上运动,造山后的伸展含矿流体进入减压扩容空间沉淀形成超大型金矿床。成矿作用发生在从印支期挤压造山向燕山期伸展转变的构造转换期。该模式与本文得到的成矿年龄和初始比值相吻合。

小秦岭车仓峪钼矿成因研究:辉钼矿Re-Os年龄及黄铁矿微量元素制约

车仓峪钼矿位于小秦岭中生代娘娘山花岗岩体与太华群基底的接触带内,矿体发育在由一组X节理控制的石英脉内。本文对车仓峪钼矿开展了辉钼矿Re-Os定年以及黄铁矿微量元素LA-ICP-MS原位分析工作。所得辉钼矿Re-Os模式年龄为133.8±4.3Ma和132.7±2.2Ma,表明车仓峪钼矿的成矿年龄为早白垩世,与娘娘山岩体的成岩年龄一致。辉钼矿样品的Re含量较低,为83×10-6和86×10-6,指示了成矿物质可能来源于I型花岗岩——娘娘山花岗岩。对与辉钼矿共生的黄铁矿进行LA-ICP-MS微量元素原位分析,发现黄铁矿中Ni含量低（4.5×10-6～76.1×10-6,平均17.4×10-6）,表明其来源应该是酸性岩,也就是其围岩娘娘山花岗岩。综合辉钼矿定年以及黄铁矿微量元素分析结果,车仓峪钼矿应该是早白垩世娘娘山花岗岩侵位时,由岩浆冷凝分异出的成矿流体充填和交代围岩形成。同时,小秦岭燕山期Mo矿化并不伴随Au矿化,结合已有资料,从侧面说明燕山期可能并不是小秦岭金的主成矿期。

安徽铜山铜矿床硫化物Re-Os定年及其地质意义

安徽铜山矽卡岩型铜矿床是长江中下游成矿带的重要矿床之一,其2件辉钼矿样品和2件黄铁矿样品的Re-Os同位素年龄分别为150.70±1.14～151.22±1.11Ma和148.73±3.22～152.50±6.69Ma,4件样品的等时线年龄为150.98±0.78Ma(MSWD=0.68,误差2σ)。这一结果表明,铜山铜矿形成于晚侏罗世,而非早白垩世。考虑到前人获得的长江中下游成矿带的成矿年龄介于134Ma和144Ma之间,我们认为长江中下游成矿带的成矿作用主要发生在侏罗纪-白垩纪之交,与构造体制由挤压转向伸展的过程同步。