【摘要】 铁氧化物-铜-金(Iron Oxide-Copper-Gold,IOCG)矿床是Hitzman et al.(1992)提出的一个新矿床类型。该概念的提出与澳大利亚Olympic Dam超大型矿床的发现有关,一定程度上促进了世界上同类新矿床的发现,引起工业界和学术界的广泛关注。中国IOCG矿床的研究起步较晚,在IOCG概念提出后很长一段时间内,并没有国内外公认的IOCG矿床报道。近年来,通过对一些Fe-Cu矿床的实例研究,目前已初步确立中国西南康滇地区、东准噶尔北缘和东天山阿齐山-雅满苏等Fe-Cu成矿带具有类似于IOCG的成矿特征,并且在矿床形成时代、机制及构造背景等成因问题上取得诸多进展。成矿时代上,康滇Fe-Cu成矿省形成于元古代,包括有～1. 65和～1. 0Ga两期主成矿事件,分别对应于区域上的两期板内岩浆作用,说明Fe-Cu矿化与大陆裂谷背景相关。东准噶尔北缘和东天山阿齐山-雅满苏成矿带均形成于古生代,分别为295～320Ma和～380Ma,被认为可能与陆缘盆地闭合有关。三个成矿带中Fe-Cu矿床围岩均为火山-沉积地层、均具有早期Fe矿化和晚期Cu矿化为主的特征且大部分矿床与同期侵入岩体没有明显空间关系,但在蚀变矿物组合及金属元素富集程度、流体特征等方面仍存在一些差别。例如康滇成矿省的蚀变组合以成矿前区域Na化、Fe矿化期Fe-Na-(Ca)化及铜矿化期K化和碳酸盐化等为特点;矿体在空间上常与大小不等的热液角砾岩筒共生;各矿床不同程度地富集REE、Mo、Au、Co等金属;成矿流体上早期以高温、中高盐度的岩浆热液为主,而成矿晚期则有更多非岩浆流体(盆地水、地层水或大气降水等)的加入。这些特点与世界上典型的IOCG矿床(特别是前寒武纪矿床)基本一致,因此目前为止,康滇成矿省作为中国的典型IOCG矿床而受国内外认可的程度相对较高。东准噶尔北缘与东天山阿齐山-雅满苏成矿带矿化特征较为相似,最新研究显示这些矿床中非岩浆流体(如盆地卤水、地层水等)对Fe-Cu矿化的贡献更大、成矿发生于陆缘盆地闭合期等,可能与南美中安第斯成矿带IOCG矿床更为类似。但是,部分矿床在成矿前均显示有明显的矽卡岩化,甚至个别矿床中矿体、岩体和矽卡岩具紧密时空关系而类似于矽卡岩矿床;多数矿床除Fe和Cu外,所含金属元素比较单一。这些特点一定程度上导致这两个矿带Fe-Cu矿床归属于矽卡岩还是IOCG矿床的问题上仍存在不少争议,尚待进一步的探索和讨论。基于目前的研究现状,本文也对中国IOCG矿床今后研究中值得关注的问题提出了一些设想和展望,包括不少矿床Fe-Cu矿化空间上分离的原因、不同地球化学行为差异较大的成矿元素(如Co、Ni与REE、U、Mo等)在矿床中均有富集的原因等方面。更多还原

【Abstract】 Iron oxide copper-gold( IOCG) deposits are a new group of hydrothermal Fe-Cu deposits,the concept of which was recently proposed by Hitzman et al.( 1992) initially due to the discovery of the giant Olympic Dam Fe-Cu-U deposit in Australia. Such a definition has triggered new discoveries of similar deposits worldwide,thus attracting extensive concerns from academy and industry societies. Researches on IOCG deposits in China are rare in past few years,and no typical IOCG deposits were reported for a long time until recent. Recent case studies on some Fe-Cu deposits in China have revealed several potential IOCG provinces in China,including the Kangdian in SW China,northern margin of East Junggar and Aqishan-Yamansu( Eastern Tianshan) Fe-Cu belts in East Tianshan,NW China. The Fe-Cu deposits in the Kangdian province are Proterozoic in ages,but involving two mineralization events of ～1. 65 Ga and ～1. 0 Ga. Both events are synchronous with within-plate rifting-related magmatism in the region,and thus were considered to be related to continental rifting setting. On the other hand,the Fe-Cu deposits in both the northern margin of Eastern Junggar and Aqishan-Yamansu( Eastern Tianshan) Fe-Cu belts are Plaeozoic in ages,forming at ～380 Ma and 295～320 Ma,respectively.Geochemical studies on the coeval magmatism in both belts indicated that the Fe-Cu deposits in the northern margin of Eastern Junggar and Aqishan-Yamansu belts have formed during closure of rifting basins in continental margins. The Fe-Cu deposits in the three belts are broadly similar in terms of mineralization styles,such as the hosting rocks as volcanic-sedimentary sequences,a paragenetic sequence of early Fe and late Cu mineralization stages,and no clearly spatial relationships of ore bodies with synchronous intrusions.However,there are also minor differences in terms of alteration and metal assemblages. For example,compared to the other two belts,Fe-Cu deposits in the Kangdian Fe-Cu province were characterized by pre-ore,regional Na alteration,Fe-Na-( Ca) ateration in Fe stage and K-carbonate alteration in Cu stage; by the close associations of ore bodies with breccia pipes; by variably enrichments of REE,Mo,Au and Co; and by a fluid evolution involving magmatic-hydrothermal fluids at early stages and more contributions of nonmagmatic fluids( basinal brines,meteoric water) at late stages. These characteristics of the Kangdian Fe-Cu deposits are similar to those of typical IOCG deposits worldwide( particularly the Precambrian ones),thus the Kangdian province as typical IOCG province is well recognized in the research society. In contrast,recent studies indicated that Fe-Cu deposits in the northern margin of Eastern Junggar and Aqishan-Yamansu belts were similarly formed during closure of basins in continental margins,and nonmagmatic fluids play relatively important roles on the Fe-Cu mineralization. These studies show that the deposits are more likely comparable with the Mesozoic IOCG deposits in central Andes. However,it is important to note that some of deposits in the two belts contain remarkable,pre-ore skarn-type alteration that is,in few cases,temperally and spatially associated with ore bodies and intrusions,and most of them do not contain a number of metals in addition to Fe and Cu. These features are more or less responsible for the dabate on the affinities of these deposits( IOCG or skarn). In this paper,we have also proposed that some important issues regarding the origin of IOCG deposit in China still desever further studies,including the mechanisms for spatially separation of Fe and Cu mineralization in some deposits and factors controlling enrichments of various elements that have different geochemical behaviors( e. g.,Co-Ni & REE-UMo).更多还原