滇东南茶花寨金矿床载金黄铁矿LA-ICPMS原位微量元素组成与地质意义

右江盆地是世界上卡林型金矿床最集中的地区之一,盆地南缘的滇东南地区是其重要组成部分。茶花寨金矿床为滇东南地区产于印支运动不整合面附近的代表性金矿床,黄铁矿为主要的载金矿物,其环带特征明显,为认识该区卡林型金矿成矿作用提供了理想的实例。本文在野外考察及镜下观察的基础上,通过LA-ICPMS分析技术,对茶花寨金矿床中不同期次黄铁矿开展了原位微量元素组成分析,以总结不同成矿阶段金的富集特征与关键控制因素。研究结果表明,该矿床黄铁矿存在3个期次：沉积成因的Py1,包括草莓状黄铁矿Py1a和环带状黄铁矿核部Py1b,交代成因的中间环带Py2,热液成因最外侧环带Py3。其中,Py1b富集Sb、Pb、Zn等元素,Py2富集As、Co、Ni,Py3则具有较高的Au、As、Cu、Sb含量和稍高的Se、Hg、Tl含量。三者对比显示,Py2中As含量最高,Py1b和Py2除As以外的其他微量元素含量接近或Py2中含量稍低,二者Co/Ni比值均在0.1附近,表明Py2为Py1b受热液交代改造形成;而Py3中微量元素组成与Py1b和Py2差异明显,指示其热液成因,且Py3中Co、Ni含量相较Py1b和Py2更低...     

安徽铜陵新桥铜硫金矿床的成因:来自两类黄铁矿微形貌学、地球化学特征的证据

新桥矿床是长江中下游成矿带铜陵矿集区内大型铜金硫矿床。本文以矿床中的黄铁矿为研究对象,在详细的野外观察和室内鉴定的基础上,将矿床中的黄铁矿分为胶状黄铁矿(Py I)和半自形-自形黄铁矿(Py II)两种类型。通过场发射扫描电镜(FE-SEM)和等离子激光质谱(LA ICP-MS)对两类黄铁矿的矿物相、形貌、微结构和微量元素成分进行研究。FE-SEM分析结果表明,Py I基本由极细粒黄铁矿组成,以自形-半自形立方体晶形为主,粒径大约100~500nm,而Py II主要为粒度为50~100μm,以八面体和五角十二面体晶形态为主,两类黄铁矿的形貌和微结构特征明显不同。LA-ICP-MS分析测试显示,Py I中相对富含As、Se、Te等元素,而Py II中成矿元素Cu、Pb、Zn、Au、Ag的含量则比Py I型黄铁矿明显偏高,分别为792.0×10-6、2125×10-6、1.67×10-6、0.29×10-6和190.7×10-6,且Bi、Co、Ni、V、Ti、Mg、Cr、Cd、Al、Mn等微量元素含量较Py I均明显偏高1~2个数量级。在综合分析黄铁矿的结构形态和微量元素组成特征的基础上,本文认为Py I可能形成于晚古生代海底热水沉积环境,Py II形成于中生代岩浆热液环境。新桥铜金硫多金属矿床的成矿作用包括了海西期同生沉积成矿作用和燕山期与岩浆活动有关的热液成矿作用。晚侏罗世-早白垩世广泛发育的强烈岩浆侵入及与之有关的热液活动,对矿床的最终形成起了主导作用,提供了Cu、Au等主要成矿物质。     

山东莱州曲家金矿黄铁矿微量元素对成矿过程的指示

曲家金矿位于我国重要的蚀变岩型金矿矿集区之焦家金矿带的中段，矿床赋存标高为-726～-1 334 m。为研究黄铁矿的演化及其对金成矿过程的指示，运用LA-ICP-MS分析黄铁矿原位微量元素含量，结合岩相学观察和点群分析对黄铁矿进行了分类。发现黄铁矿中Co、Ni、As等微量元素主要以类质同像形式赋存，而Au、Ag、Cu、Zn、Pb、Bi等元素主要以纳米级、微米级矿物包裹体形式赋存。黄铁矿主要分为5种类型：富Co型Py1,富Ni型Py2,富Au、As型Py3,富Au、Ag、Pb、Bi型Py4及“干净”型Py5。黄铁矿微量元素特征指示成矿物质可能主要来源于前寒武纪变质基底岩石和中生代岩浆岩，少量来源于地幔，成矿热液可能属变质热液、岩浆热液和浅部大气降水的混合成因。不同类型黄铁矿反映成矿热液由富Co、Ni经富As、Au向富Pb、Bi、Au、Ag演化。Py1和Py2形成后受构造活动影响发生强烈破碎，裂隙表面对热液中金络合物增强的吸附作用促使金在裂隙中沉淀，对金的富集成矿可能起重要作用。Co、Ni含量较低，同时Au、Ag、As、Pb、Bi等元素含量较高的黄铁矿与成矿作用有密切关系。另外，黄铁矿中C...     

滇西北红山铜多金属矿床的成因类型:黄铁矿和磁黄铁矿LA-ICPMS微量元素制约

红山大型铜多金属矿床位于云南中甸地区,包括红山、红牛和恩卡3个矿段,矿体主要呈层状-似层状产于石榴石夕卡岩、角岩、大理岩和硅质岩之中,或者呈细脉浸染-网脉状赋存于深部隐伏花岗斑岩体之中。目前学术界关于该矿床的成因类型仍然存在不同认识,本文使用激光剥蚀电感耦合等离子体质谱仪(LAICPMS)对矿区硅质岩、夕卡岩矿石中的黄铁矿和磁黄铁矿进行了微区原位成分的测试,进而根据微量元素特征来约束矿床的成因。分析结果表明,不同产状的黄铁矿具有明显不同的微量元素组成,硅质岩中的黄铁矿相对富集Ti、Mn、Ni、As、Pb、Bi、Te、Ag和Sb等微量元素,Co/Ni比值小于1,表现为典型同生沉积黄铁矿的微量元素特征;而夕卡岩矿石中的黄铁矿则相对富集Co和Cu,亏损As、Se和Sb等低温元素,且Co/Ni比值多数大于1,显示高温岩浆热液黄铁矿的微量元素特征。此外,硅质岩中磁黄铁矿的Co、Ni和Se等微量元素组成与黄铁矿的组成十分类似,表明它们的化学组成主要受到沉积环境的控制。夕卡岩中的磁黄铁矿与黄铁矿相比强烈亏损Co,这可能归因于早期黄铁矿沉淀时带走了大量的Co,从而导致残余热液中Co浓度的大幅降低。通过研究,我们还查明红山矿区黄铁矿中的Co、Ni、As和Se等元素主要以固溶体的形成存在,而Pb、Bi、Ag、Cu和Mn等元素则主要以显微包裹体的形式存在。黄铁矿和磁黄铁矿中Pb和Bi均表现为正相关关系,暗示它们可能以显微包裹体或纳米微粒的形式分布于这两种硫化物中。结合野外地质产状与前人已有研究,我们认为红山矿区至少存在两期成矿作用,其中晚三叠世沉积成岩作用形成的黄铁矿富集了一定的Ag、Bi和Pb等成矿元素,而晚白垩世的岩浆-热液活动则带来了大量的Cu和Mo等金属元素,从而在红山矿区形成了复合型的Cu-Mo-Pb-Zn-Ag多金属矿化体系。     

安徽铜陵新桥Cu-Au-S矿床黄铁矿微量元素LA-ICP-MS原位测定及其对矿床成因的制约

激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)是一种固体微区分析新技术。用该技术来分析矿床中硫化物的微量元素组成可以为研究成矿流体特征、矿床成因及找矿勘探提供有关的科学信息。文中以安徽铜陵矿集区内新桥Cu-Au-S矿床中的黄铁矿为研究对象,在详细的野外观察和室内鉴定的基础上,将矿床中的黄铁矿分为具有沉积特征的胶状黄铁矿(PyⅠ)、具有变形重结晶和热液叠加作用特征的细粒他形黄铁矿(PyⅡ)和具热液成因特征的中—粗粒自形黄铁矿(PyⅢ)3种类型。LA-ICP-MS原位微量元素测定结果显示,PyⅠ中相对富含Ti、Co、Ni、As、Se、Te;PyⅡ继承了PyⅠ中富含Ti、Co、Ni、As、Se、Te、Bi的特征,同时还含有不均匀分布的少量成矿元素(Cu、Pb、Zn、Au、Ag);PyⅢ中成矿元素Cu、Pb、Zn、Ag、Au以及Bi元素的含量较高,Co、Ni、As的含量较低。在元素赋存状态方面,Co、Ni、As、Se和Te均以类质同象的形式进入到了黄铁矿的晶格中;Bi在PyⅡ中主要以含Bi矿物的微细包裹体形式存在,而在PyⅢ中的Bi还部分取代了Fe而占据了晶格;Cu、Pb、Zn、Au、Ag这些成矿元素中,Cu和Zn分别以黄铜矿和闪锌矿的矿物包裹体存在于黄铁矿中;PyⅡ中所含的少量Au、Ag,可能分别以自然金和自然银的形式存在,而在PyⅢ中Au可能主要以银金矿的形式存在,Ag除了以银金矿的形式存在以外还可能赋存于黄铁矿中含铋的矿物包裹体内;Pb主要赋存于黄铁矿中的方铅矿或含铋矿物的包裹体中。在综合分析黄铁矿的结构形态和微量元素组成特征的基础上认为,PyⅠ型黄铁矿可能形成于前人提出的晚古生代海底沉积或喷流沉积环境,PyⅡ和PyⅢ型黄铁矿分别形成于中生代区域构造变形-热液叠加改造的过渡环境和热液环境,PyⅡ和PyⅢ的形成时间相近。新桥矿床的形成可能经历了晚古生代海底沉积或喷流沉积期和燕山期热液期,胶黄铁矿主要形成于沉积成矿期,而矿床中成矿物质Cu、Pb、Zn、Au、Ag等主要来自燕山期岩浆侵入作用形成的热液成矿系统。     

安徽铜陵冬瓜山矿床矿石硫化物环带及地质意义

安徽冬瓜山矿床是铜陵矿集区内一个重要的大型铜(金)矿床,颇受关注,成因认识分歧较大。矿床内块状硫化物矿石中普遍发育以黄铁矿为核部、黄铜矿为中间带、磁黄铁矿为边部带的硫化物环带。这些环带核部黄铁矿多呈自形-半自形晶,黄铜矿呈他形晶围绕黄铁矿沉淀,磁黄铁矿呈他形分布在黄铜矿外围,内带常被外带硫化物溶蚀交代。硫同位素分析结果显示,环带中硫化物矿物的硫同位素(δ34S=1.6‰~5.1‰)具有岩浆硫源特征,同时从核部黄铁矿到中间带黄铜矿,再到边部磁黄铁矿δ34S值逐渐降低。以上特征表明环带从内到外硫化物之间并非平衡共生关系,而是黄铁矿、黄铜矿和磁黄铁矿先后依次晶出。硫化物环带核部粗粒黄铁矿(粒径大于1.5cm)的Co、Ni含量分别为292×10-6~1504×10-6和32.7×10-6~39.9×10-6,Co/Ni=7.32~46.0(平均26.7),与海底火山喷流沉积型黄铁矿的Co、Ni特征基本一致。核部黄铁矿由颗粒中心向边缘,Fe/S原子比值、Mo和Co含量先逐渐升高,再逐渐降低,而Cu、Zn等成矿元素主要富集于颗粒边缘,并向边缘有逐渐升高趋势。与此同时,细粒黄铁矿(粒径小于0.5cm)中的Cu、Zn等元素的含量明显高于粗粒黄铁矿。环带中三种硫化物矿物的REE配分曲线和微量元素蛛网图极为相似,相对富集LREE、Rb、Th等元素,而亏损Nb、Ta、Zr、Hf、Sr、Ba和HREE等元素,由环带核部到边部δEu逐渐减小,与矿区石英二长闪长(玢)岩表现出较高的相似性。以上特征综合分析表明,冬瓜山铜(金)矿床中硫化物环带经历了以下形成过程:石炭纪海底喷流沉积作用在矿区形成沉积黄铁矿,到燕山期,在区内强烈的构造-岩浆活动作用下,致使早期沉积的黄铁矿首先发生变质重结晶作用,形成粒状黄铁矿,随后岩浆热液对其进行叠加改造,并在岩浆热液作用下相继围绕粒状黄铁矿增生,依次沉淀出热液型黄铁矿、黄铜矿和磁黄铁矿,最终形成硫化物环带。这一认识,结合硫化物环带中元素及硫同位素特征进一步表明冬瓜山铜(金)矿床的形成先后经历了古生代海底喷流沉积成矿作用和燕山期岩浆热液成矿作用,矿床中的成矿物质(特别是Cu、Zn等成矿元素)主要来源于燕山期岩浆热液,但石炭系海底喷流沉积作用也提供了部分物质(例如,Fe、S、Mo、Co和Ni等)。此外,环带中微量元素的变化特征表明,随着硫化物环带的形成,成矿热液系统的温度、硫逸度和氧逸度逐渐降低和(或)p H值升高。     

粤北东坑铀矿床黄铁矿LA-ICP-MS微量元素特征及其意义

东坑铀矿床是粤北地区代表型花岗岩型铀矿床之一,复杂的成矿过程制约了人们对其成因的理解。文章依据成矿期次,将其中黄铁矿划分为4类:矿前期粗晶萤石-梳状石英中的黄铁矿(Py Ⅰ)、成矿期早阶段红色微晶石英中的自形-半自形黄铁矿(Py Ⅱ)、主成矿阶段沥青铀矿中的胶状-他形黄铁矿(Py Ⅲ)以及晚成矿阶段自形-半自形细粒黄铁矿(Py Ⅳ)。微量元素分析结果表明,黄铁矿中Co、Ni、As、Se主要以类质同象的形式存在,而U、Pb、Cu、Zn、Bi等元素则以矿物包裹体的形式存在。Py Ⅰ和Py Ⅱ具有相对较高的As、Tl含量和较低的Co、Ni以及U、W、Mo、V、Ti含量,表明其形成温度较低;Py Ⅲ具有最低的As、Tl含量和最高的Co、Ni、Ti、V、Mn、U、Mo含量,暗示流体温度相对较高,且辉绿岩或深源流体可能提供了部分物质;Py Ⅳ的As、Tl、Sb略微升高,Co、Ni及Se、U、Mo、W、Ti、V、Mn、Cu、Zn则降低,且其Co/Ni值变化较大,结合结构特征认为其形成于流体快速降温过程。不同矿床黄铁矿微量元素的对比结果表明,东坑铀矿床主成矿期黄铁矿与竹山下“交点型”和辉绿岩中黄铁矿类...     

胶东焦家金成矿带2420~3206 m垂深金矿物和黄铁矿微量元素特征

在胶东莱州吴一村地区完成的3266.06 m深钻,是目前焦家金成矿带最深见矿钻孔,研究钻孔揭露的深部矿石中金矿物及黄铁矿微量元素特征,对探讨深部成矿作用演化具有重要意义。笔者采取深钻中2420~3206 m垂深的岩（矿）芯样品进行了详细的岩相学和矿相学研究,结合扫描电镜和电子探针微区分析,研究了矿石中金矿物的赋存状态和成分。对不同成矿阶段形成的黄铁矿进行了LA-ICPMS微量元素分析。研究结果表明,深部矿石中载金矿物主要为黄铁矿,其次为石英、黄铜矿、方铅矿,可见金主要以自然金和银金矿的形式存在,以晶隙金和裂隙金为主,其次为包体金。与浅部金矿床比较,深部金的成色较高。黄铁矿分为6种类型,第Ⅰ成矿阶段形成富Co型黄铁矿Py1,第Ⅱ成矿阶段形成富Ni型黄铁矿Py2a和Py2b,第Ⅲ成矿阶段形成富Au、As型黄铁矿Py3a和富Au、Ag、Pb、Bi型黄铁矿Py3b,第Ⅳ成矿阶段形成贫微量元素黄铁矿Py4。其中,Py1和Py2a发生强烈破碎,裂隙表面对热液中的Au络合物产生吸附作用,对金沉淀富集起重要作用。黄铁矿中Co、Ni、As等微量元素主要以类质同象形式赋存,而Au、Ag、Cu、Pb、Zn、Bi等主要以纳米级、微米级矿物包体形式赋存。Pb+Bi、Cu+Pb+Zn、Te+Bi与Au+Ag呈明显正相关,而Au与As相关性较差。黄铁矿中Co、Ni含量较低,而Au+Ag+As或Au+Ag+Pb+Bi+Cu含量较高指示成矿有利。另外,黄铁矿中Co、Ni含量较高,并且破碎强烈,成矿相关元素含量较高也指示成矿有利。     

甘肃寨上金矿黄铁矿特征与成因

甘肃寨上金矿是我国重要的卡林型金矿床,发育多种特征的黄铁矿、毒砂、黝铜矿、黄铜矿等金属硫化物。黄铁矿贯穿整个地质过程,对其进行研究可深入理解成矿作用。观察发现,黄铁矿可分为3个世代。第1世代黄铁矿为莓球状黄铁矿(Py1A)和多孔海绵状黄铁矿(Py1B)2类;第2世代中粗粒自形黄铁矿(Py2);第3世代粗粒黄铁矿(Py3)。Py1A呈莓球状,直径介于10～50μm,w(Co)/w(Ni)小于1,w(S+As)/w(Fe)大于2,部分黄铁矿因受到热液改造,莓球中w(Co)/w(Ni)大于1,w(S+As)/w(Fe)小于2;Py1B呈多孔海绵状,w(Co)/w(Ni)大于1,w(S+As)/w(Fe)小于2。Py2呈中粗粒五角十二面体,w(Co)/w(Ni)介于1.41～3.78,w(S+As)/w(Fe)由内向外逐渐升高,介于1.93～2.02,w(Au)/w(As)介于0.023～0.108。Py3呈粗粒立方体晶,周围发育石英压力影,w(Co)/w(Ni)介于1.36～1.39,w(S+As)/w(Fe)介于1.98～2.00。结合地质背景分析认为,黄铁矿微晶直接聚集形成Py1A(莓球状),或在松散状态下经胶结作用形成Py1B(多孔海绵状),并遭受热液叠加改造。Py2(中粗粒五角十二面体)由含矿热液环绕多孔海绵状核部直接结晶形成,Py3(粗粒自形立方体)由晚期热液结晶形成,并同时遭受构造变形活动。该区黄铁矿的特征对于判别地质环境有标型意义。     

黔中猫场杨家洞矿段铝土矿中富钴黄铁矿的发现与意义

铝土矿中伴生有Li、Ga、V、Cr、REE、Sc、Co、Ni、Nb、Zr、W等关键金属.黔中猫场铝土矿是我国最大的隐伏铝土矿矿床,已发现伴生有镓、钪和锂等关键矿产资源,然而对硫铁矿中可能伴生的关键金属尚未引起足够的重视,本文系统开展了猫场杨家洞矿段中不同类型含矿岩系及矿石中黄铁矿的精细矿物学工作.结果表明,杨家洞矿段黄铁矿具有复杂的结构和成因,可分为沉积黄铁矿(PyⅠ)和热液黄铁矿(PyⅡ)等2大成因.前者以草莓状或细粒结构为特征;后者从早到晚进一步划分为3个世代:PyⅡ-1、PyⅡ-2和PyⅡ-3,其中PyⅡ-2呈不规则状交代或增生于PyⅡ-1颗粒的边部,PyⅡ-3呈脉状或网脉状切穿早期的黄铁矿.电子探针分析结果表明,PyⅡ-2具有明显高于其他世代黄铁矿的Co和As含量,分别高达9.31％和2.98％,揭示猫场硫铁矿中钴元素的富集与后期热液活动密切相关.Co与Fe明显的负相关性反映Co主要以类质同象的方式赋存于黄铁矿晶格内,PyⅡ-2和PyⅡ-1截然的接触界线和不同的化学成分暗示富钴黄铁矿PyⅡ-2主要由耦合的溶解-再沉淀作用形成.猫场铝土矿中富钴黄铁矿的发现为猫场矿区硫铁矿的综合回收利用乃至黔中地区铝土矿中伴生关键金属类型找矿提供了新的方向.     

Genesis of the Bianjiadayuan Pb-Zn polymetallic deposit,Inner Mongolia,China:Constraints from in-situ sulfur isotope and trace element geochemistry of pyrite

The Southern Great Xing'an Range(S(GXR)which forms part of the eastern segment of the Central Asian Orogenic Belt(CAOB)is known as one of the most important Cu-Mo-Pb-Zn-Ag-Au metallogenic belts in China,hosting a number of porphyry Mo(Cu),skarn Fe(Sn),epithermal Au-Ag,and hydrothermal veintype Ag-Pb-Zn ore deposits.Here we investigate the Bianjiadayuan hydrothermal vein-type Ag-Pb-Zn ore deposit in the southern part of the SGXR.Porphyry Sn± Cu± Mo mineralization is also developed to the west of the Ag-Pb-Zn veins in the ore field.We identify a five-stage mineralization process based on field and petrologic studies including(i)the early porphyry mineralization stage,(ii)main porphyry mineralization stage,(iii)transition mineralization stage,(iv)vein-type mineralization stage and(v)late mineralization stage.Pyrite is the predominant sulfide mineral in all stages except in the late mineralization stage,and we identify corresponding four types of pyrites:Pyl is medium-grained subhedral to euhedral occurring in the early barren quartz vein;Py2 is medium-to fine-grained euhedral pyrite mainly coexisting with molybdenite,chalcopyrite,minor sphalerite and galena;Py3 is fine-grained,subhedral to irregular pyrite and displays cataclastic textures with micro-fractures;Py4 occurs as euhedral microcrystals and forms irregularly shaped aggregate with sphalerite and galena.LA-ICP-MS trace element analyses of pyrite show that Cu,Pb,Zn,Ag,Sn,Cd and Sb are partitioned into pyrite as structurally bound metals or mineral micro/nano-inclusions,whereas Co,Ni,As and Se enter the lattice via isomorphism in all types of pyrite.The Cu,Zn,Ag,Cd concentrations gradually increase from Pyl to Py4,which we correlate with cooling and mixing of ore-forming fluid with meteoric water.Py2 contains the highest contents of Co,Ni,Se,Te and Bi,suggesting high temperature conditions for the porphyry mineralization stage.Ratios of Co/Ni(0.03-10.79,average 2.13)and sulphur isotope composition of sulfide indicate typical hydrothermal origin for pyrites.The δ~(34)S_(cDT) values of Pyl(0.42‰-1.61‰,average1.16‰),Py2(-1.23‰to 0.82‰,average 0.35‰),Py3(—0.36‰to 2.47‰average 0.97‰).Py4(2.51‰--3.72‰,average 3.06‰),and other sulfides are consistent with those of typical porphyry deposit(-5‰to 5‰),indicating that the Pb-Zn polymetallic mineralization in the Bianjiadayuan deposit is genetically linked to the Yanshanian(Jurassic-Cretaceous)magmatic-hydrothermal events.Variations of δ~(34) S values are ascribed to the changes in physical and chemical conditions during the evolution and migration of the ore-forming fluid.We propose that the high Sn content of pyrite in the Bianjiadayuan hydrothermal vein-type Pb-Zn polymetallic deposit can be used as a possible pathfinder to prospect for Sn mineralization in the surrounding area or deeper level of the ore field in this region.     

胶东三山岛金矿床黄铁矿显微结构和微量元素特征:对金富集机制的指示

三山岛金矿床是位于胶东金矿集区西北部的超大型破碎带蚀变岩型金矿床.该矿床细致的矿相学及元素地球化学研究尚有不足,限制了对其金富集机制及过程的理解.基于野外地质调查和室内矿相学研究将该矿床划分为4个成矿阶段:石英?绢云母?黄铁矿阶段(I)、石英?金?黄铁矿阶段(I I)、石英?金?多金属硫化物阶段(I I I)和碳酸盐?...     

云南都龙超大型锡锌多金属矿床中闪锌矿微量及稀土元素地球化学特征

云南马关都龙锡锌多金属矿床位于滇东南老君山锡锌钨多金属成矿区南部,是我国三大锡石硫化物矿床之一,目前对其矿床成因认识存在较大分歧。本文采用ICP-MS对都龙矿床中闪锌矿微量元素及稀土元素组成进行分析,以探讨该矿床成矿作用,为甄别已有成因观点提供证据。结果表明,矿床中闪锌矿以富集Fe、Mn、In、Co、Sn和贫Cd、Ga、Ge、Ni等元素为特征,成矿温度属于中—高温,其微量元素组成与白牛厂矿床(与燕山晚期花岗岩有关的矽卡岩型矿床)中的闪锌矿非常相似,和远源矽卡岩型铅锌矿床(核桃坪和芦子园)中闪锌矿存在一定差异,明显有别于喷流沉积型铅锌矿床(云南澜沧老厂和广东大宝山)中闪锌矿。此外,该矿床闪锌矿稀土配分模式多为轻稀土元素富集中等的向右倾斜曲线,以LREE/HREE值高、Eu负异常明显和Ce异常不明显为特征,与矿区燕山晚期隐伏花岗岩稀土元素特征基本一致,成矿物质来源以矿区燕山晚期隐伏花岗岩为主。结合近期矿山开采和地质勘探所揭露的矿化和矽卡岩蚀变的垂向分带等矿床地质特征,认为云南马关都龙锡锌多金属矿床属于与燕山晚期花岗岩有关的矽卡岩型多金属矿床,其中层状矽卡岩的形成应为成矿流体顺层交代的结果,矿化类型和围岩蚀变的分带与隐伏岩体的距离有关。     

Trace elements mineral chemistry of sulfides from the Woxi Au-Sb-W deposit,southern China

The Woxi Au-Sb-W deposit is one of the largest polymetallic ore deposits in the Xuefengshan Range, southern China, hosted in low-grade metamorphosed Neoproterozoic volcaniclastic rocks. The orebodies of the deposit are predominantly composed of banded quartz veins, which are strictly controlled by bedding and faults. Petrographic observations and geochemical results are reported on the occurrence of Au and properties of the ore-forming processes for different stages in the deposit. The veins extend vertically up to 2 km without obvious vertical metal zoning. The ore-forming process can be subdivided into four mineralization stages: Pre-ore stage; Early stage (scheelite-quartz stage); Middle stage (pyrite-stibnite-quartz stage); and Late stage (stibnite-quartz sage). Four types of pyrite (Py0, Py1, Py2, and Py3) were identified in the ores and host-rock: Py0 occurs as euhedral grains with voids in the core, ranging in size from 50 to 100 μm and formed mainly in the Pre-ore stage and Early stage; Py1 occurs as subhedral grains. Small grains (around 10 μm) of Py1 form irregularly shaped clusters of variable size ranging from tens to hundreds of μm and mainly formed in the Middle stage; Euhedral-subhedral fine-grained Py2 formed in the Late stage; Minor subhedral fine-grained Py3 was deposited in the Late-stage. Stibnite is widely distributed in the Middle and Late stage ore veins. No systemic difference was recognized in mineralogical features among stibnite formed in different stages. In addition to native gold, the lattice bound Au⁺¹ widely exists in Py1 and Py2 in the deposit, and widespread Py1 is considered as the main Au-bearing mineral with the highest Au contents. Most elements (such as Co, Ni, Cu, As, Sb, Ba, and Pb) are considered to occur as solid solution within the crystal lattice and/or invisible nanoparticles in sulfides minerals. The Co/Ni ratio of most pyrite is lower than 1, suggesting that the metals in the ore-forming fluid are sourced from sedimentary rocks. The coupled behavior between Au and As; Au and Sb suggests that the substitution of As and Sb in pyrite can enhance the incorporation of Au. Variation of trace elements in pyrites of different stages suggests some information on the mineralization processes: Large ion lithophile elements (such as Ba and Pb) are enriched in Py0 indicating that water-rock reaction occurred in the Early stage; Fine-grained Py1 with a heterogeneous distribution of elements suggests fast crystallization of pyrite in the Middle stage.     

Metal source of gold deposits in the Jiaoxibei area,Eastern China: Insights from trace element analysis of gold and pyrite

The metal source of gold deposits in the Jiaoxibei area, eastern China, has been investigated by many researchers, but no consensus has been reached so far. In this study, three typical gold deposits, the Xinli, Jiaojia, and Dayingezhuang deposits, were selected for trace element analysis of gold and pyrite to constrain the metal source. Pyrite from these three deposits has similar morphological and compositional characteristics, and can be divided into three types: Py1 with euhedral to subhedral textures, Py2 with subhedral to anhedral textures with micro-fractures, and Py3 with subhedral to anhedral textures and intergrowing polymetallic sulfides. Among them, Py2 and Py3 were formed in the main ore-forming stage and they are the dominant host minerals of visible gold. In these deposits, visible gold occurs mainly in micro-fractures or as inclusions in Py2 and Py3. Most of the pyrite has extremely low concentration of invisible gold, indicating that visible gold in the Jiaoxibei district is not a product of the remobilization of invisible gold from earlier pyrite. Both Py2 and Py3 are characterized by low Co concentration of <100 ppm and Co/Ni ratio of <1, which are similar to those of pyrite in sedimentary rocks. Therefore, ore-forming metals of these gold deposits in the Jiaoxibei district may originate mainly from a sediment-related metal source.     

Trace Element Record of Pyrite from Diverse Deposits-Examples from the Dabaoshan Polymetallic Deposit of Northern Guangdong,South ChinaEI北大核心CSCD

The Dabaoshan polymetallic deposit, located in the middle Nanling metallogenic belt, is an important and representative W-Mo-Cu-Pb-Zn deposit in the northern Guangdong. The deposit is characterized by a complex combination of ore-forming elements, containing 0.86 Mt Cu, 0.85 Mt Zn, 0.31 Mt Pb, 0.14 Mt WO3 at grades of 0.86%, 12%, 1.77% and 0.12%, respectively. Due to different mineral association and occurrence, mineralization at Dabaoshan can be defined as three types: porphyry W-Mo mineralization, skarn Mo-W mineralization and strata-bound sulfide mineralization. Pyrite from the three-mineralization types has different textures and element compositions. EMPA mapping analysis suggested that distribution of Co, Ni, and As is nearly homogeneous, whilst As in pyrite from the stratabound sulfides shows weak irregular zoning. LA-ICP-MS analyses of pyrite suggested that the three type have distinctive trace element characteristics even though the concentrations of the trace elements are relatively low. Cobalt, Ni, As and Se substitutes Fe and S in pyrite respectively while Cu, Zn, Sn Sb are mainly represented by chalcopyrite, sphalerite, cassiterite and stibnite inclusions enclosed in pyrite. Ni and Ag are rich in the pyrite from the stratabound mineralization. The results suggested that the trace element characteristic of pyrite can be used to: a) study the occurrence of trace element in pyrite; b) imply the chemical-physical conditions; c) trace the regional ore-forming substance and ore forming process. The stratabound mineralization is formed during the volcano eruption during the Devonian then and overprinted by the deep source material and multiple ore-forming fluids in the Yanshanian period. © 2018, Science Press. All right reserved.     

胶东三山岛金矿床黄铁矿原位微区微量元素特征及对矿床成因的指示

胶东地区是我国最大金成矿聚集区,其金矿床的成因长期以来一直存在很大争议,三山岛金矿床是胶东地区最大的金矿床,通过采用LA-ICP-MS分析不同阶段黄铁矿中微量元素组成,可以探讨成矿流体演化及成矿物质来源。根据野外地质特征及岩相学观察,结合SEM结构分析将三山岛金矿床的黄铁矿分为3个阶段,6个亚类,即黄铁绢英岩化带(Py1)中包裹大量绢云母和石英的Py1-a和表面光滑的Py1-b,石英—黄铁矿±菱铁矿脉(Py2)中富含矿物包裹体的Py2-a和与菱铁矿共生且表面光滑的Py2-b,石英—多金属硫化物脉(Py3)中有很多细粒多金属硫化物包裹体的Py3-a和表面光滑的Py3-b。3个阶段黄铁矿晶格中金含量均很低,大部分小于1×10^-6,金主要以可见金形式存在。从早阶段到晚阶段黄铁矿中Au与Ag,Cu,Pb,Sb有较好的正相关性,且含量有逐渐增加的趋势。最早阶段黄铁矿中Co+Ni的含量很高(最高为9268×10^-6),反映了早期黄铁矿可能来源于岩浆岩源区,后期Co/Ni值逐渐降低,暗示了成矿流体温度逐渐降低。结合地质特征和黄铁矿微量元素研究,表明三山岛金矿床成矿物质可能来源于深部岩浆热液储库,通过地震泵机制沿断裂构造多次侵位成矿。     

Fluid source and physicochemical conditions of the polymetallic mineralization in Gawuch Formation,Kohistan Island Arc,NW Pakistan

The Cu-Sb-Pb polymetallic vein deposit is hosted by metavolcanics rocks of the Gawuch Formation at the Kaldom Gol area of the northwest Kohistan arc terrain in northern Pakistan. The mineralization is closely associated with the dioritic to granodioritic rocks of the Lowari pluton, which was intruded into the Gawuch metavolcanics. Details of ore characterization and processes of ore genesis of this evidently hydrothermal mineralization are not well documented. Integrating petrographic, mineral-chemical and isotopic investigations, this study aims to comprehend the source of hydrothermal fluids, geochemical evolution, mineral inclusions and physicochemical conditions of the Cu-Sb-Pb polymetallic vein deposit in Gawuch metavolcanics in the Kohistan arc terrain in northern Pakistan. The mineralization is distinguished into three types of ore-gangue associations: Type Ia, Type Ib, and Type II. The textural study revealed two pyrite generations: (i) Py1 displaying euhedral to subhedral habits and containing scarce inclusions, and (ii) Py2 occurring as anhedral grains hosting abundant inclusions. Type Ia is characterized by Py1 associated with abundant quartz (Qz) showing comb texture, sericite (Ser), and minor chlorite (Chl). Type Ib comprises Qz + Ser + Chl and Py2, chalcopyrite (Ccp), and magnetite (Mag). Type II is represented by mosaic quartz, rhombic adularia, and bladed calcite, and the ore minerals fahlore and galena. Alteration zones composed of Qz-Ser ± Chl and Qz-Ser-Chl, surround Type I (a, b) and Type II veins, respectively. Fahlore and galena mostly replace pyrite of Type Ia and chalcopyrite of Type Ib. In addition, malachite, azurite, hematite and covellite occur as secondary (supergene) minerals. The Co/Ni ratios (>1) of Kaldom Gol pyrites suggest that the ore-forming fluids were hydrothermal in origin and Py1 and Py2 solidified at 221–304 °C and 225–261 °C, respectively. The LA-ICP-MS time-resolved depth profiles confirm the existence of sphalerite, and chalcopyrite inclusions in pyrite (Py1 and Py2) and millerite, bravoite, vaesite, Au-tellurides, native Au and galena inclusions in chalcopyrite and fahlore. Sulfur isotope compositions of pyrites (δ³⁴S = Py1, −0.58 to +2 ‰; δ³⁴S = Py2, −0.24 to +2.04 ‰) indicate that the ore-forming fluids were derived from magmatic source (s). The mineral assemblage, hydrothermal alterations, textures, temperature and δ³⁴S of pyrites suggest that the Cu-Sb-Pb polymetallic mineralization at Kaldom Gol represents an intermediate-sulfidation type of epithermal deposit.     

小秦岭东桐峪金矿床黄铁矿LA-ICP-MS微量元素特征及其成矿意义

位于华北克拉通南缘的小秦岭地区是我国仅次于胶东的大型金矿床集中区,但金矿床的成矿物质来源及成因问题一直存在较大争议.以华北南缘小秦岭矿集区东桐峪金矿床中的黄铁矿作为研究对象,在黄铁矿显微结构研究的基础上利用LA-ICP-MS对黄铁矿的微量元素进行原位分析,为进一步认识东桐峪金矿床及区内其他同类型矿床的成因提供新的资料和制约.东桐峪金矿床的黄铁矿从早到晚依次划分为3个世代(PyⅠ、PyⅡ和PyⅢ).PyⅠ主要形成于粗粒黄铁矿-石英阶段,颗粒粗大且自形程度高,呈星点状或斑点状赋存于乳白色石英脉中.PyⅡ主要形成于石英-中细粒黄铁矿阶段,呈半自形-他形结构且裂隙发育,常被晚期石英、多金属硫化物、自然金等矿物充填.PyⅢ主要形成于多金属硫化物阶段,常呈他形粒状结构与黄铜矿、方铅矿及闪锌矿等硫化物密切共生.LA-ICP-MS分析结果显示,PyⅠ中As平均含量为16.63×10-6,Au、Ag和Te含量较低且常位于检测限以下;相较而言,PyⅡ中As含量稍低,而Au、Ag和Te含量略高(其中Au含量为0.10×10-6~0.59×10-6);PyⅢ中Au、Ag和Te含量差异较大且显著升高,其中Au、Te含量最高可达35.58×10-6和79.79×10-6,而As含量较低且大部分数值低于检测限;不同世代黄铁矿的Co/Ni比值基本上都大于1,且PyⅢ的Co、Ni含量和Co/Ni比值明显低于PyⅡ和PyⅠ.以上结果表明,东桐峪金矿床的载金矿物黄铁矿中As的含量很低,金的富集与As无关;不同世代的黄铁矿中Au、Ag和Te之间存在显著且稳定的线性正相关关系,暗示金矿化与Te关系密切.另外,第3世代黄铁矿(PyⅢ)中Au、Ag及Te存在显著富集,指示Te(而不是As)在金和银的迁移、搬运、富集、沉淀等过程中具有重要作用.华北克拉通南缘小秦岭地区晚中生代大规模的金成矿作用及金矿床中普遍存在Te-Au-Ag矿物,且黄铁矿中As含量低、Te含量高等特征,暗示该区金矿床的成矿物质/成矿流体可能来自深部岩浆的脱挥发分或地幔脱气作用,而与区域变质作用的关系不大.