造山带金矿研究现状与存在的问题

造山带金矿是当前矿床学和大地构造学研究热点,Groves等(1998)、Goldfarb等(2001)基于太古"地壳连续模式"(Groves,1993)的研究工作以涉及资料量大、应用成果新、考虑地质因素多而居于这一领域前沿.但是,目前众多研究对前寒武地质与显生宙地质的宏观差异、世界金矿一些总体规律及若干具体大地构造背景等尚认识不足.显生宙缺乏太古代大规模火成活动,已知金矿中很少同变质深成型(hypozonal),以浅变质岩为围岩的金矿区中没有相当的中-深变质岩为围岩的金矿."太古绿岩带"金矿区同样也缺乏浅变质岩为围岩的金矿.华北地块周边金矿主要形成在侏罗-白垩纪,明显晚于大兴安岭造山带和秦岭-大别山造山带,而与欧亚陆缘近南北向燕山期岩浆弧有关.距俯冲带较远、缺乏蛇绿混杂岩与大规模变质作用、发育大量中-新生代盆地及广泛地壳减薄等表明,中国东部与北美科迪勒拉(Cordillera)造山带晚中生代地质存在宏观差异,燕山期岩浆弧可能形成于一个以伸展为主导的环境,大量以花岗岩为围岩或相对太古变质围岩后生成因金矿及其成矿的大地构造背景值得深入研究,弄清各类显生宙金矿与造山带的关系是推进造山带金矿研究的关键.

Orogenic gold deposits:Studies,advances and debates

Orogenic gold deposits are the focus of attention of many tectonic and mineral geologists. Groves et al. (1998) and Goldfarb et al's (2001) studies, based on the crustal continuum model for late-Archaean lode-gold deposits (Groves, 1993), are marked by involvement of large-amount of new data and consideration for many factors. However, many current studies failed to notice certain macroscopic disparities between Archaean and Phanerozoic geological entities rationally and understand global gold occurrences and some tectonic settings properly. The Phanerozoic, identified by far too limited igneous activity, lacks the "hypozonal" type of and any other higher-grade metamorphic rock-hosted gold deposits in a low-grade metamorphic rock-hosted gold camp, whereas the Archaean is likewise devoid of low-grade metamorphic rock-hosted gold deposits in a greenstone belt. The gold deposits in the margin of the North China Block (NCB) are primarily of Jurassic-Cretaceous age, notably younger than the Late Palaeozoic Greater Hinggan (on the north of NCB) and Triassic Qinling-Dabieshan (on the south of NCB) orogens. Those gold deposits, mostly hosted by Archaean intermediate-high grade metamorphic rocks and Late Mesozoic granitoids, are basically ascribed to the giant magmatic arc along the Eurasian Margin, which is Yanshanian in age (Jurassic-Cretaceous) and nearly N-S orientated. Eastern China appears to differ from the North America Cordillera in the Late Mesozoic interval as to being further from the subduction zone, lacking ophiolitic complexes and large-scale metamorphism, having numerous basins and thinning in the crust, suggesting that the magmatic arc was probably formed in a back arc basin-like extensional setting. Further clarifying the connection of Phanerozoic gold deposits to relevant orogens may be the key to understanding orogenic gold deposits throughout the geological age.