粤北新洲推覆构造同推覆期构造地球化学的动态学研究

DYNAMIC STUDY ON THE SYNTHRUSTING TECTONOGEOCHEMISTRY OF THE XINZHOU NAPPE STRUCTURE,NORTHERN GUANGDONG PROVINCE

粤北新洲推覆构造从尾缘片体(BK_1)至前缘片体(BK_7)的渐进发育过程,代表了推覆构造的递进变形历史.在推覆运动早期,Au、Pb、Cu、As、Bi、Hg 等成矿元素从推覆体后缘迁出,晚期在前缘富集成矿.因此,外来系统中金矿成矿预测靶区,应该是在推覆体前缘片体 BK_4～BK_7.同时,在推覆运动早、中期形成的韧性推覆断层带中,Au、Hg、As、Cu 等元素的富集过程完全受同推覆期增量剪应变历史的控制,从而造成在断层带有限剪应变强度中心两侧的最大增量剪应变强度中心所限制的区段内,形成剪切带型金矿体。

The progressive developing process from the rear nappe sheet(BK_1)to the frontal nappe sheet(BK_7)of the Xinzhou nappe structure in Northern Guangdong repre- sents the progressive deformation history of the nappe structure.During the early stage of the thrusting,ore-forming ele- meats(Au,Pb,Cu,As,Bi,Hg)moved out from the rear nappe sheets(BK_1-BK_3),then migrated and concentrated in the frontal nappe sheets(BK_4-BK_7)during the late stage of the thrusting.Thus,the prospecting target area of gold deposit in the allochthon should be might the frontal nappe sheets(BK_4-BK_7).At the same time,within the ductile thrusting fault zone formed during the early and middle stages of the thrusting,the concentrating process of the ore-forming elements (Au,Hg,As,Cu)is completely controlled by the progressive shear strain history,which forms shear-zone type gold ore body within the ductile shear zone domain enclosed by the two highest incremental shear strains on the side of the highest finite shear strains in the ductile thrusting fault zone.