试论主要类型矿床的形成深度与最大延深垂幅

On the ore-forming depth and possible maximum vertical extension of the major type ore deposits

在大量典型矿床实地调查和国内外综合对比研究的基础上,基于深部找矿的现实需要和存在问题,本文首先回顾评述了主要矿床类型的原始成矿深度,按受控于中下地壳尺度大规模岩浆堆积体的超深成岩浆矿床与受控于流体渗透率制约的中上地壳深成、中成和浅成岩浆热液矿床序列展开。在此基础上尝试探讨主要类型矿床的最大延深垂幅,探讨分析了以Bushveld层状岩体和Voisey s Bay小岩体为代表的铜镍矿床、驱龙为代表的斑岩铜矿床、Muruntau为代表的造山型金矿、胶东金矿省的已控制延深垂幅、剥蚀程度以及深部可能的延深空间。内生矿床系统具有很宽的成矿深度范围,大型层状岩体的成矿深度可逾20 km,最大矿化垂直延深幅度可达6~8 km。岩浆热液矿床的最大成矿深度以地壳尺度流体渗透的下限为底界,其中造山型金矿床成矿深度最大(约12~15 km),伟晶岩和花岗岩型矿床次之,斑岩型矿床居中(约2~6 km),浅成低温金银矿床深度最浅(1 km至近地表);相应的最大延深垂幅则依次可达4~7 km、2~3 km和1 km。评述了高渗透性的聚矿构造空间、成矿作用顶峰、合适的矿床保存条件等控制因素及部分标志。并对如何确定合理统一的成岩成矿深度(压力)的估算方法以及确定最大成矿深度与矿化体系最大延深幅度的理论依据、判断标志、综合辨识方法体系等未来研究方向进行了展望。

Based on a large number of field investigations and comparative studies of typical mineral deposits,and in considerations of the existing problems and practical needs of deep ore prospecting and evaluation,we first review in this paper the depth of ore deposits for the main deposit types,from the ultra-deep magmatic deposits controlled by large-scale magmatic accumulation in the middle-to-lower crust,to the deep,middle and shallow magmatic-hydrothermal deposits controlled by fluid permeability in the middle and upper crust.On this basis,we attempt to explore the maximum vertical extension of the major type ore deposits,and discuss the constrained depth of mineralization,degree of denudation,and possible vertical extension at depth for the copper-nickel(-chromite-PGE)deposits represented by the Bushveld and Voisey's Bay,the porphyry copper deposits represented by Qulong,the orogenic gold deposits represented by Muruntau,and the Jiaodong gold province.The depth and vertical extension of hypogene mineralization associated with magmatic ore deposit can vary greatly;for example,the depth of mineralization in a layered igneous complex can extend to 20 km,with vertical extension ranging from 6 to 8 km.The maximum depth of magmatic-hydrothermal deposits is at the bottom of the lower crust where fluid penetration occurs.Oroganic gold deposits have the greatest depth,about 12-15 km,followed by pegmatite and granite deposits;porphyry deposits are in the middle,about 2-6 km;and the epithermal Au-Ag deposits have the shallowest depth of less than 1 km to the surface.The corresponding vertical extension of these deposits ranges in 4-7 km,2-3 km,and 1 km,respectively.The controlling factors and some indicators are reviewed,such as high permeability of ore accumulating structural space,peak of mineralization,and suitable preservation conditions.Future research on the depth of mineralization may focus on such issues including how to determine a reasonable and uniform estimation method for the depth(pressure)of hypogene mineralization,as well as the theoretical basis,judgement markers and comprehensive identification method for determining the maximum depth and vertical extension of deposits.