新疆望峰金矿成矿流体的He、Ar同位素示踪

本文采用稀有气体同位素质谱方法,通过分析望峰金矿石中载金黄铁矿流体包裹体He、Ar同位素组成,对成矿流体进行示踪研究。结果显示,黄铁矿流体包裹体3He/4He比值为0.00473～0.01079Ra,40Ar/36Ar比值为301～413,具地壳放射性成因氦同位素组成和大气降水成因氩同位素组成,总体显示由大气降水改造而成的地壳流体特征。望峰金矿成矿流体中He同位素组成异常,是成矿前大气降水与高U、Th含量古老容矿围岩作用遭受放射性成因4He稀释、成矿时发生流体减压沸腾综合作用的结果,Ar同位素组成异常是成矿前大气降水下渗获取容矿围岩放射性成因40Ar的结果,成矿流体是大气降水深循环的产物。     

对新疆萨日达拉金矿成矿流体的He、Ar同位素示踪

采用稀有气体同位素质谱方法,通过分析萨日达拉金矿载金黄铁矿中流体包裹体的He、Ar同位素组成,对成矿流体进行示踪研究。结果表明,萨日达拉金矿黄铁矿流体包裹体中He同位素组成变化范围较大,R/Ra值为0.34~1.59,显示壳幔混合特征,二元混合模型计算结果显示以地壳放射性成因氦为主,并有地幔氦的加入;Ar同位素组成较均一,~(40)Ar/~(36) Ar值为305~359,平均336,~(36)Ar/~(38)Ar值为5.34~5.44,平均5.40,显示叠加有部分放射性成因~(40)Ar的大气降水成因氩同位素组成。综合分析结果表明,萨日达拉金矿成矿流体为由大气降水深循环改造而成的地壳流体,其所具有的地幔He同位素组成应继承自下部地壳中隐伏的壳幔混合成因地质体。     

闽中梅仙式铅锌银矿床矿质来源的硫、铅同位素示踪及成矿时代

福建闽中地区是我国又一个新的、重要的火山岩容矿块状硫化物铅锌多金属成矿带。为查明梅仙式铅锌银矿床的金属成矿物质来源和成矿时代,本文对其中5个主要矿床进行了矿石矿物和围岩的硫、铅同位素测试和同位素地质年代学研究。结果表明,不同矿床矿石硫化物的硫同位素组成变化范围较小且平均值接近于零,δ34S介于-3.5‰~ 5.6‰,平均 2.0‰,表明硫主要为岩浆来源,火山直接喷发和从容矿火山岩中淋取皆是可能的机制。大部分矿床矿石铅以放射性成因为特征(206Pb/204Pb>18.140、207Pb/204Pb>15.584、208Pb/204Pb>38.569),且矿石铅同位素值均大于围岩,指示铅可能主要是由容矿火山岩淋滤而来。根据矿床地质特征和同位素地质测年数据,厘定出两次重要的铅锌成矿作用,即中-新元古代海底火山喷流沉积同生成矿(赋矿围岩单颗粒锆石U-Pb法、Sm-Nd等时线法和40Ar-39Ar法年龄介于933~1788Ma)和燕山期岩浆热液叠加改造成矿(侵入岩锆石SHRIMPU-Pb和Rb-Sr等时线年龄为127~154Ma)。     

四川大渡河金矿田成矿流体来源的氦氩硫氢氧同位素示踪

四川大渡河金矿田位于扬子地台西缘金成矿带北段,受大渡河剪切带控制。本文以该矿田黄金坪、白金台子、黑金台子金矿为例,根据对黄铁矿流体包裹体氦氩同位素、黄铁矿硫同位素以及与黄铁矿共生的石英流体包裹体的氢氧同位素组成测定,讨论了大渡河金矿田成矿流体的来源。结果显示,该金矿田黄铁矿流体包裹体中的~3He/~4He变化较小,为0.16～0.86Ra,而~(40)Ar/~(36)Ar的变化较大,为298～3288;而黄铁矿δ~(34)S同位素变化范围较窄,一般为0.7‰～4.2‰,集中于2.5‰～3‰,显示硫地幔来源的特点;石英流体包裹体的氢、氧同位素分别为-2.6‰～ 3.64‰和-39.13‰～-108.23‰,说明成矿流体为岩浆水和大气降水的混合流体。本文认为大渡河金矿田成矿流体是地幔流体与地壳流体的混合作用的结果,而以地壳流体占主导地位。其中,地幔流体为与下伏隐伏岩体有关的岩浆水,而地壳流体端元则是含有一定放射成因Ar的大气降水,并且温度小于200℃。     

新疆阿尔泰南缘克因布拉克铜锌矿床成矿流体的氦-氩同位素示踪

克因布拉克铜锌矿床赋存于二长花岗岩外接触带的上志留—下泥盆统康布铁堡组黑云石英片岩、变质石英砂岩中,矿体呈似层状、透镜状及脉状。本文对铜锌矿石中的黄铁矿流体包裹体氦和氩同位素组成进行了研究。黄铁矿中流体包裹体的4He含量为0.241×10-7~5.288×10-7cm3STP/g,Rc/Ra值为0.95~1.89,幔源He的含量为14.1%~28.8%,表明成矿流体中氦主要来源于地壳,存在幔源氦的加入。40Ar含量为4.345×10-8~7.752×10-8cm3STP/g,40Ar/36Ar比值变化于302.10~436.96,40Ar*含量为2.2%~32.4%,表明成矿流体中存在含有放射性成因氩的大气降水加入。结合矿床地质特征及氢、氧、碳、硫同位素特征,认为成矿流体来源于高温深源壳幔混合成因的岩浆流体,具大气氩同位素组成特征的低温大气降水。     

新疆准噶尔北缘索尔库都克铜钼矿氦-氩同位素组成及地质意义

索尔库都克铜钼矿床位于准噶尔北缘,矿体呈似层状、透镜状、脉状产于中泥盆世北塔山组安山岩和矽卡岩中。采用稀有气体同位素质谱法,对矿床中绿帘石矽卡岩、安山岩和矿石3种产状的黄铁矿中流体包裹体氦和氩同位素组成进行测试分析。测试结果显示,黄铁矿中流体包裹体的4He含量为(0.882 1~13.341 0)×10-8cm3STP/g,3He/4He为0.88~1.76 Ra(Ra为大气中的3He/4He,Ra=1.4×10-6),幔源He占13.27%~26.93%,表明成矿流体中氦主要来源于地壳。40Ar含量为(4.237 6~13.970)×10-8cm3STP/g,40Ar/36Ar为301.07~331.55,40Ar*含量占1.71%~10.87%,表明成矿流体中Ar主要来源于大气降水。3种产状的黄铁矿中氦、氩同位素组成及特点相似,结合矿床流体包裹体和稳定同位素研究,认为成矿流体来源于壳-幔相互作用的岩浆流体和大气降水,矿床的形成与安山岩和矽卡岩关系密切,暗示矿床成因为矽卡岩型。     

新城金矿稳定同位素地球化学特征及成矿物质的来源

新城金矿是胶东金矿集区招远—莱州成矿带的一个"焦家式"蚀变型金矿床。本文主要通过C、H、O、S、Pb同位素研究,对新城金矿成矿流体、物质来源和成矿作用进行探讨和研究。新城金矿矿石中δD值范围为-116‰~-91‰,δ18O水值范围为3.8‰~7.2‰,表明成矿流体早期来源于岩浆水,成矿晚期混入大气降水。矿石硫化物、郭家岭花岗闪长岩、玲珑花岗岩和胶东群δ34S平均值分为7.9‰、6.5‰、8.5‰和6.2‰,认为矿石硫具有对矿区地层及岩浆岩硫的继承性。硫化物矿石206Pb/204Pb=17.115~17.414,207Pb/204Pb=15.460~15.577,208Pb/204Pb=37.912~38.196,显示铅具有壳幔混合来源的特征。碳、氢、氧、硫、铅同位素反映新城金矿成矿物质和流体主要来源于深部岩浆。     

江西相山矿田硫铅同位素地球化学特征

为查明江西相山矿田内铅锌矿和铀矿床的成矿物质来源,对与铅锌矿、铀矿有关的矿石矿物进行了S、Pb同位素研究,结果显示,与铅锌矿有关的金属矿物δ34S值为1.3‰~4.7‰,同铀矿伴生的黄铁矿δ34S值为7.9‰~14.9‰;赋矿围岩、基底变质岩、铀矿床黄铁矿和铅锌矿硫化物的206Pb/204Pb、207Pb/204Pb及208Pb/204Pb比值整体上有逐渐降低的趋势,均表现出放射性成因铅的特征,不同岩石或矿石的样品铅同位素组成范围基本一致。结合前人研究,说明铅锌矿和铀矿并非来自同一次成矿事件;铅锌矿的成矿期次具有阶段性,硫源具有均一性,主要以深部硫源为主,在其向上迁移的过程中有少量基底变质岩中的硫加入,按照硫化物共生矿物对计算出铅锌矿的成矿温度:早阶段为424~382℃,晚阶段为331~290℃,属中高温热液矿床;铀矿的硫源具有地层硫特征,主要来自于基底变质沉积岩。铀矿床伴生的黄铁矿铅同位素组成比铅锌矿硫化矿的铅同位素组成更具放射性成因铅,铅锌矿的铅源主要与上地壳基底变质岩有关,铀矿的铅源主要以相山火山-侵入杂岩体为主,但是可能还具有少量幔源铅参与。     

粤北诸广南部铀矿田流体包裹体的氦氩同位素组成及成矿流体来源示踪

粤北诸广南部铀矿田是我国重要的花岗岩型铀矿产地之一,有关诸广南部花岗岩型铀矿田的成因,多年来一直存在较大的争议。本文以诸广南部铀矿田典型铀矿床成矿期萤石、方解石和黄铁矿中流体包裹体为测试对象,研究了成矿流体的He、Ar同位素地球化学。研究表明,萤石流体包裹体的~3He/~4He比值为0. 021～0. 186Ra,~(40) Ar/~(36)比值为298. 4～2515. 7;方解石流体包裹体的3He/4He比值为0. 027～0. 209Ra,~(40) Ar/~(36)比值为295. 9～327. 2;黄铁矿流体包裹体的3He/4He比值为0. 021～1. 543Ra,~(40) Ar/~(36)比值为326. 9～1735. 1; He-Ar同位素系统显示成矿流体的3He/4He比值略高于地壳氦同位素特征值(0. 01～0. 05Ra),但低于幔源氦同位素特征值(6～9Ra),~(40) Ar/~(36)比值接近或高于大气氩的同位素组成(~(40) Ar/~(36)=295. 5),成矿流体为壳-幔混合来源。结合H-O、He-Ar、C和Sr等多元同位素证据表明,成矿流体由两个端元组成:一是含有一定放射性成因Ar的大气降水的地壳流体,二是含幔源He的地幔流体。进一步研究表明,受NNW向断裂控制的棉花坑、书楼丘、长排等铀矿床受地幔流体影响比较大,而受NE向断裂控制的蕉坪、东坑、烟筒岭铀矿床受大气降水影响比较大。     

新城金矿稳定同位素地球化学特征及成矿物质来源探讨

新城金矿是胶东金矿集区招远—莱州成矿带的一个"焦家式"蚀变型金矿床。本文主要通过C、H、O、S、Pb同位素研究,对新城金矿成矿流体、物质来源和成矿作用进行探讨和研究。新城金矿矿石中δD值范围为-116‰~-91‰,δ18O水值范围为3.8‰~7.2‰,表明成矿流体早期来源于岩浆水,成矿晚期混入大气降水。矿石硫化物、郭家岭花岗闪长岩、玲珑花岗岩和胶东群δ34S平均值分为7.9‰、6.5‰、8.5‰和6.2‰,认为矿石硫具有对矿区地层及岩浆岩硫的继承性。硫化物矿石206Pb/204Pb=17.115~17.414,207Pb/204Pb=15.460~15.577,208Pb/204Pb=37.912~38.196,显示铅具有壳幔混合来源的特征。碳、氢、氧、硫、铅同位素反映新城金矿成矿物质和流体主要来源于深部岩浆。     

内蒙古阿右旗卡休他他夕卡岩型铁金矿床地质特征及控矿因素探讨

内蒙古阿右旗卡休他他铁金矿床属于夕卡岩-热液叠加型矿床。特定岩性、岩浆岩、构造是形成该种类型矿床的基本条件：辉长岩和石英闪长岩与围岩的接触带控制矿床的产出部位,岩体接触带的夕卡岩控制着铁、金矿体的分布范围,层间破碎带和构造裂隙带则控制着铁、金矿体的形态。铁矿化产于中基性岩体和围岩接触的夕卡岩带中,金矿体产在富铁矿体及其附近的夕卡岩中,金矿和铁矿是同一地质作用过程中不同阶段的产物,矿床可能形成于海西中期。     

加拿大萨斯喀彻温省索西(Southey)钾盐矿床特征及成因

加拿大萨斯喀彻温省索西(Southey)钾盐矿床,主要赋存于中泥盆统的Elk Point(埃尔克波因特)群上部Prairie Evaporite(草原蒸发岩)组。钾盐矿层稳定,似水平状展布,埋深约1250~1550 m;钾盐矿物主要有钾石盐(KCl)和光卤石(KCl·Mg Cl2·6H2O),矿石品位高,w(K2O)可达11.17%~21.85%,是世界少有的高品质钾盐矿床。文章分别从构造位置、古地理条件、物源补给、沉积韵律和成矿过程等多个方面综合分析了索西钾盐矿床的成因。     

论凤山铜矿床的再生成因

凤山铜矿床产于中元古界昆阳群绿汗江组凤山段，其下伏为中元古代晚期的滇中裂陷槽中的狮山铜矿床。凤山铜矿床矿体呈脉状、巢状、囊状，切割围岩，形态产状受断裂构造及狮山段紫色层“刺穿体”的控制，是典型的后生矿床。矿石物质成分（以黄铜矿、斑铜矿为主）、黄铁矿的Co含量（0．6％）及Co/Ni比值（75．71）和硫化物的δ^34S值均继承了狮山铜矿床的特点；矿石具碎斑状、角砾状，细脉状和网脉状等后生矿石构造，凤山铜矿床黄铜矿、斑铜矿对各种波长入射光的反射率均高于狮山铜矿床黄铜矿、黄铜矿的Cu、Au、Ag含量高于狮山铜矿的黄铜矿，而S、As、Zn含量低于狮山矿的黄铜矿。基于上述特征，提出了凤山铜矿床的再生成矿模式。凤山铜矿床的成矿物质来自下伏的狮山铜矿床及狮山段紫色层细碧质火山角砾岩，经后期非含矿热液溶解而沿构造上升，而后在上覆地层的构造中沉淀、富集而形成再生矿床。     

云南白牛厂银多金属矿床成因

对云南白牛厂超大型银多金属矿床的地质、地球化学特征及矿床形成的长期性及多阶段性的研究认为:白牛厂银多金属矿床是热水沉积—叠生成因矿床,早期呈现寒武纪的热水同生沉积成矿作用,晚期为燕山期花岗岩浆热液成矿作用。该矿床是热水沉积成矿作用与岩浆热液成矿作用叠加成矿的产物。     

云南大平掌铜多金属矿床硫、铅、氢、氧同位素地球化学

对云南大平掌铜多金属火山岩型块状硫化物矿床的矿石矿物和火山岩围岩的Ｓ、Ｐｂ同位素及脉石矿物、硅 化岩、硅质岩等的Ｈ、Ｏ同位素地球化学特征进行了研究,认为矿床中大多数硫来源于热液对火山岩的淋滤,或直接 来源于火山喷气作用;矿石铅与火山岩铅属同一来源,且以富放射性成因铅为特征;成矿流体可能主要来源于深循环的海水与岩浆水的混合流体,而大气降水参与的可能性很小。     

新疆和田县雪凤岭锂矿床、雪盆锂矿床和双牙锂矿床地质特征及伟晶岩脉群分带初步研究

作为战略性关键金属矿产,锂矿勘查与研究已成为当今矿产勘查和地学研究的热点。项目组2017年以来通过多次野外勘查、系统取样与室内化验分析,确认在新疆和田县白龙山锂多金属矿床东部的雪凤岭一带发现了雪凤岭、雪盆和双牙3处花岗伟晶岩型锂多金属矿床。雪凤岭锂矿床由3个含矿伟晶岩脉群共计47条锂多金属矿体组成,矿体长32~360 m,厚0.9~8 m,走向110°~120°,倾角49°~78°。对雪凤岭矿区伟晶岩脉群研究,发现含矿伟晶岩脉群‒含白云母伟晶岩脉群‒块体石英长石伟晶岩脉群‒含黑色电气石伟晶岩脉群‒块体石英长石伟晶岩脉群‒含白云母伟晶岩脉群‒含矿伟晶岩脉群具对称分带特征,进而在距雪凤岭1550 m南部的双牙山和雪盆沟发现较好的锂矿体,其中双牙锂矿床主矿体长850 m,厚12 m,出露最宽处近100 m;雪盆锂矿床3条锂矿体,长800~1200 m,厚4~8 m,向西合成一个矿体,厚12~20 m。各矿体Li2O品位0.6%~4.02%。伴生BeO品位0.04%~0.15%,Rb2O品位0.10%~0.23%,Nb2O5品位0.007%~0.047%,Ta2O5品位0.003%~0.046%。预测雪凤岭、雪盆、双牙3个矿床334资源量共计Li2O为7.1886×105 t,BeO为2.648×103 t,Rb2O为1.433×103 t,Nb2O5为3.387×103 t,Ta2O5为1.727×103 t,雪凤岭一带有望成为一个超大型锂多金属稀有金属矿产基地。     

Silver-Bearing and Associated Minerals in El Zancudo Deposit, Antioquia, Colombia

The occurrence and the chemical compositions of ore minerals (especially the silver‐bearing minerals) and fluid inclusions of the El Zancudo mine in Colombia were investigated in order to analyze the genetic processes of the ore minerals and to examine the genesis of the deposit. The El Zancudo mine is a silver–gold deposit located in the western flank of the Central Cordillera in Antioquia Department. It consists mainly of banded ore veins hosted in greenschist and lesser disseminated ore in porphyritic rocks. The ore deposit is associated with extensive hydrothermally altered zones. The ores from the banded veins contain sphalerite, pyrite, arsenopyrite, galena, Ag‐bearing sulfosalts, Pb‐Sb sulfosalts, and minor chalcopyrite, electrum, and native silver. Electrum is included within sphalerite, pyrite, and arsenopyrite, and is also partially surrounded by pyrite, arsenopyrite, sphalerite, and tetrahedrite. Native silver is present in minor amounts as small grains in contact with Ag‐rich sulfosalts. Silver‐bearing sulfosalts are argentian tetrahedrite–freibergite solid solution, andorite, miargyrite, diaphorite, and owyheeite. Pb‐Sb sulfosalts are bournonite, jamesonite, and boulangerite. Two main crystallization stages are recognized, based on textural relations and mineral assemblages. The first‐stage assemblage includes sphalerite, pyrite, arsenopyrite, galena and electrum. The second stage is divided into two sub‐stages. The first sub‐stage commenced with the deposition and growth of sphalerite, pyrite, and arsenopyrite. These minerals are characterized by compositional growth banding, and seem to have crystallized continuously until the end of the second sub‐stage. Tetrahedrite, Pb‐Cu sulfosalts, Ag‐Sb sulfosalt, and Pb‐Ag‐Sb sulfosalts crystallized from the final part of the first sub‐stage and during the whole second sub‐stage. However, one Pb‐Ag‐Sb sulfosalt, diaphorite, was formed by a retrograde reaction between galena and miargyrite. The minimum and maximum genetic temperatures estimated from the FeS content of sphalerite coexisting with pyrite and the silver content of electrum are 300°C and 420°C, respectively. These estimated genetic temperatures are similar to, but slightly higher than the homogenization temperatures (235–350°C) of primary fluid inclusions in quartz. The presence of muscovite in the altered host rocks and gangue suggest that the pH of the hydrothermal solutions was close to neutral. Most of the sulfosalts in this deposit have previously been attributed as the products of epithermal mineralization. However, El Zancudo can be classified as a xenothermal deposit, in view of the low pressure and high temperature genetic conditions identified in the present study, based on the mineralogy of sulfosalts and the homogenization temperatures of the fluid inclusions.     

Geology, Geochemistry and Minerogenesis of the Shijuligou Zinc–Copper Deposit in Gansu, China

Abstract: The Shijuligou deposit was separated by an arcuate ductile shear zone cross the center of the deposit region, resulting in the difference between the southern and northern ore bodies. The lead (Pb) isotopic data of ores of the Shijuligou copper deposit have averages of 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb in 17.634, 15.444, and 37.312, respectively. It has been shown that ore-forming metals originated from intrusive and extrusive rocks in the upper part of ophiolites. The sulfur isotopic data of pyrite and chalcopyrite in the northern part change from +7.61‰ to +8.09‰ and +4.95‰ to +8.88‰ in the southern part. Isotopes of δ18O in the Shijuligou copper deposit are between +11.1‰ and +18.6‰, with the calculated δ18OH2O at +0.65‰. It is suggested that the mineralized fluid is a mixture of magma fluid, meteorological water, and seawater through circulating and leaching metals from the volcanic rocks. The zircon uranium-lead (U–Pb) dating of gabbro is 457.9±1.2 Ma, and the lower crossing age of the discordant and concordia curves of pyroxene spilite of zircon is 454±15 Ma. It is indicated that the Shijuligou deposit formed in a new ocean crust (ophiolite) of the back-arc basin in the late Ordovician. Mineralization should occur in the intermittence period after strong volcanic activity, and the age should be the late Ordovician. Moreover, the mineralization of ophiolite-hosted massive sulfide deposits in the ancient orogenic belt of the late Ordovician in the northern Qilian Mountains was controlled by the primary fault/fracture, with the forming of a metallogenic hydrothermal system by a mixture of volcanic magma fluid and seawater, which circularly leached the metallogenic metals from the volcanic rocks, resulting in their accumulation. The ore bodies were transformed with morphology and metallogenic elements. Jasperoid is an important sign for prospecting such deposits. There were many island arcs in the continent of China. This study provides evidence for understanding and exploration of ophiolite-hosted massive sulfide deposits in western China, especially in the area of northern Qilian Mountains.     

东天山维权银铜矿床中钴矿化发现及成因意义

新疆东天山地区是中国重要的钴成矿带之一,在多个与基性-超基性岩有关的铜镍硫化物矿床和磁海铁矿床中伴生有中小型钴矿资源。最近,笔者在研究东天山维权矽卡岩型银铜矿床物质组分的过程中,通过显微镜观察、电子探针扫描和成分分析发现了独立钴矿物辉砷钴矿,不仅代表了东天山含钴矿床的新类型,而且具有综合利用的前景。文章对维权矿床中铜银钴矿石类型、矿石中辉砷钴矿和其他主要金属矿物的赋存状态进行了研究,划分出铜矿石、铁铜矿石、含银铜钴矿石、银矿石、含钴铁铜矿石和铅银铜矿石6种矿石类型,认为它们可能是铁铜、钴、银3期成矿作用叠加的产物,钴成矿作用为独立的一期中高温热液成矿作用,含钴铁铜矿石是钴成矿作用叠加在铁铜成矿作用之上形成,而含银钴铜矿石是银成矿作用叠加在钴成矿作用之上形成。     

甘肃岷县寨上金钨矿床中钨矿特征及找矿标志

寨上矿床属于以金为主、伴生钨的多金属矿床。目前已发现15条钨矿化体,其中主要的6条钨矿体均与金矿体相重合。寨上矿区9处异常中有7处Au、W异常相重合。Au、W元素相伴生存在,局部地区形成金、钨矿化体共生的局面。钨矿物主要为白钨矿,极少量黑钨矿。白钨矿也是重要的载金矿物,金与钨关系密切。矿体主要产于碳质板岩、泥质板岩、钙质板岩等较软弱岩性地层。矿脉受控于层间或顺层断裂破碎带。矿区的主要蚀变类型有硅化、黄铁矿化,其次为碳酸盐化、绢云母化。低阻高极化异常能较准确的反映矿化带和矿脉的延伸位置。钨的水系沉积物异常和土壤异常均呈带状低值异常特征,与已知矿带吻合较好。研究成果及勘查实践证明,在该金矿化(带)体中寻找钨矿化体是最简捷的方法。