华东地区燕山期花岗质岩浆与成矿作用关系研究

华东地区是我国重要的钨、铜、铁、钼、金、银、铀、铅、锌等多种金属矿产的产业基地。本文系统总结了华东地区钦杭成矿带和武夷山成矿带等重要多金属成矿带的燕山期岩浆活动与成矿作用的时空演化规律,提出燕山期区域成岩成矿作用可划分为早、晚两期四个阶段。(1)燕山早期早阶段(180~165Ma),以I型花岗岩及埃达克质岩石为主,主要分布在钦杭结合带东段以及武夷山成矿带的闽西南坳陷区内,形成一系列斑岩型及矽卡岩型铜铅锌银多金属矿床;其中埃达克质岩是俯冲板块挤压环境下加厚(或拆沉)下地壳重熔的产物;(2)燕山早期晚阶段(165~140Ma),以S型花岗岩以及钨锡、铌钽矿床为主,主要分布于南岭成矿带,另有少量非埃达克质I型花岗岩;(3)燕山晚期早阶段(145~120Ma),为区域由挤压向伸展过渡的构造转换期,在古太平洋板块斜向俯冲所导致的大规模伸展背景下,产生了S型与I-A型花岗岩共生的局面,其中S型火山-侵入杂岩与火山热液型铀铅锌矿床关系密切;在钦杭结合带东段一线出现A型花岗岩以及伴生的钨锡铌钽矿化,其年龄(135~125Ma)略晚于S型火山-侵入杂岩,在武夷山地区岩石类型则以I型为主,并与矽卡岩型以及石英脉型钨锡铁钼矿有关;(4)燕山晚期晚阶段(120~90Ma),在强烈的伸展背景以及俯冲带向洋迁移作用下,成岩成矿事件集中在武夷山以东的沿海地区,以出现晶洞花岗岩、过碱性花岗岩等高温、浅成、高分异花岗岩类为特征,但金属成矿作用则大多与富钾的I型花岗岩类有关,在多个矿集区内形成大量的浅成低温热液型铜金银矿床。钦杭成矿带和武夷成矿带之间的成岩-成矿时空差异性主要受控于古太平洋板块俯冲过程及基底物质组成。

Yanshanian granitic magmatisms and their mineralizations in East China

East China is one of important W-Cu-Fe-Au-Ag-U and Pb-Zn industrial bases in China. In this paper, we systematically summarize Yanshanian granitic magmatisms and their mineralizations in major metallogenic belts such as Qinhang and Wuyishan metallogenic belts, and divide Early and Late metallogenic episodes as well as four metallogenic stages in East China. (1) The 1^st metallogenic stage is early stage of Early Yanshanian (180~165Ma), forming I-type and adakitic rocks and related porphyry- and skarn-type Cu-Pb-Zn-Ag deposits which dominantly occurred in eastern Qinhang metallogenic belt and southwestern Fujian depression of Wuyishan metallogenic belt, among them adakitic magmas were derived from the partial melting of the (delaminationed) thickened lower crust under compressed setting of paleo-Pacific Plate subduction; (2) The 2^nd metallogenic stage is late stage of Early Yanshanian (160~165Ma), mainly forming crust-derived peraluminous S-type granitoids and related W-Sn & Nb-Ta deposits, while minor I-type granites; (3) The 3^rd metallogenic stage is early stage of Late Yanshanian (140~120Ma). In the stage, S- and I-A type volcanic-subvolcanic complex and related hydrothermal Pb-Zn and U deposits co-existing in the region. Along Qinhang suture zone occur A-type granites and related W-Sn-Nb-Ta deposits, whose ages (125~135Ma) are slightly younger than these S-type rocks. While, the I-type granites and related skarn- or quartz vein-type W-Sn-Fe-Mo deposits intensively outcrop in the Wuyishan area; (4) The 4^th metallogenic stage is late stage of Late Yanshanian (120~90Ma), under strong extensional setting of subducted slab rollback, accompany with generation of miarolite, peralkaline granitic rocks and bimodal volcanics in the coastal region of East China, forming fruitful epithermal Au-Ag-Cu deposits, which are mainly related to high-K I-type granites. Spatial-temporal differences of magmatisms and mineralizations between both Qinhang and Wuyishan metallogenic belts were mainly controlled by the process of paleo-Pacific Plate subduction and basement materials.