沉积改造型金矿床的构造古地理控制

沉积改造型金矿床系指矿源层由正常(非火山的)沉积作用形成,经后期改造未变质或弱变质的层控型金矿床,金呈微细浸染状。该类型矿床的分布明显受古地理控制,盆地边缘相、台地前缘斜坡相、台地边缘生物礁相、局限台地相以及槽盆相,特别是两相区的过渡带是矿源层形成的有利场所。其形成的大地构造环境为不同时代的被动大陆边缘区、弧后边缘海的陆侧以及初生洋盆。矿床存在的大地构造单元以加里东期、海西—印支期冒地槽褶皱带为主。

TECTONO-PALEOGEOGRAPHIC CONTROL OF SEDIMENTO-REFORMED GOLD DEPOSITS IN CHINA

The scdimcnto-rcformcd gold deposits are referred to those stratabound gold deposits found in nonmctamorphic or slightly metamorphosed rocks and reformed in late stage, in which gold occurs in dissemination, and their source beds were formed by normal (nonvolcanic) sedimentation. The distribution of this type of gold deposits is obviously controlled by palcogcography and sedimentary environments. The basin-margin facics, platform-margin biohermal facies, platform front slope facics, restricted platform facics and trough basin facies, especially transitional zones of the two facies bolts are the sites favourable for deposition of the source beds. Impure carbonates, dark grey or black shales, siltstones, slates and fine-grained turbidites are the main host rocks. The geotectonic settings in which the source beds were deposited are passive continental margins, continental sides of backarc marginal sea and juvenile ocean basins of various times. The gold deposits in question occur mainly in the Caledonian and Hercynian-Indo-Chinese miogeosynclinal velts.