粤北晚古生代沉积盆地扩张和金属成矿作用  

LATE PALEOZOIC SEDIMENTARY BASIN-EXTENSION AND METALLOGENESIS IN THE NORTHERN GUANGDONG PROVINCE, CHINA

作　　者：杨振强[1] 陈开旭[1] 陈善庆[1] 毛晓冬[1] 蒋德和[1] 

机构地区：[1]宜昌地质矿产研究所

出　　处：《华南地质与矿产》1996年第3期23-30,共8页Geology and Mineral Resources of South China

摘　　要：晚古生代期间,粤北半地堑式裂陷盆地受控于华南大板块内的三叉张裂盆地系统.沉积盆地演化阶段包括:基底上隆、张裂、沉陷(三角洲充填)、下沉和封闭阶段.海西期盆地演化史中的沉陷至稳定早期阶段对热水成矿有利.热水(喷气)沉积矿床一般具有“三明治”式的矿石序列:底板蚀变(脉状矿石)→整合块状硫化物矿体→顶板蚀变或喷气盖层以及矿层底部见有爆发和沸腾特征.热水沉积(喷气)岩具有负的δ^(13)C和δ^(18)O值、低于正常海相硅质岩的δ^(18)O值和强烈的Eu正异常REE模式.晚古生代旋回可识别出5个与矿化层位有关的热事件:中泥盆统、上泥盆统、中石炭统、下二叠统和上二叠统.区内块状硫化物矿床绝大多数是盆地扩张期热事件的产物,而某些矿床(例如金、银、铜)则是盆地封闭阶段——印支运动(T_3—J_1)的产物.During the Late Paleozoic Era. a semi-graben subsidence basin at the northern Guan-dong area was controlled by a triple-rift-basin system after the Devonian within the South China Plate. The Late Paleozoic sedimentary evolution in the studied area shows several graben-like phases, including basement uplift, spreading, subsidence (infilled delta), down-warping and closing stages.In the Hercynian basin-evloution history, the early stages from subsidence to stable ones are favorable for the forming of hydrothermal-sedimentary (exhalative)rock/ores. The hy-drothermal metallogenesis may be expressed as a epithermal cycle activity on/beneth sea-floor including recharge and discharge zones.In most case, therefore, the hydrothermal exhalation deposit has an ore sequence of sandwich structure: footwall alteration (stringer ore)→comformable massive sulfide ore→ hang-ingwall alteration and/or exhalite cap,and have explosion and boiling features at the bottom. The exhalative limestons and marbles yeild variously negative δ13C( - 2. 6 to -8. 15‰PDB)and δ18O(-7 to - 18‰PDB) values. The δ13C-δ18O changing curves on Scotchman's (1991) diagram show a synpathetic trend. And the exhalite silica rocks yeild δ18O(12 to 21‰sMOW) which are lower than that of the normal marine silica (25 to 28‰swow). Both exhalites and ores yeild a feature of REE patterns with strongly positive Eu anomalies which are similar to that of morden discharge vent zones on deep seafloor(Barrett et al. 1990)Based on the geological and geochemical characteristics of the six studied deposits with in the Hercynian cycle (Devonian to Carboniferous System). the massive sulfide deposits may fall into two groups:(1)hosted in sediment only(e. g. Vankou Pb-Zn deposit)and (2)hosted by volcano-sedimentary cycles (e. g. Dabaoshan multimetal district). In the Hercynian cycle, five heat-events related to the mineralization are recongnized:(1) Hercynian and pyrite sedimentation in the Middle Devonian Series; (2)exhalite in the Upper Devonian Series; (3)Fe-sil

关 键 词：盆地扩张 热水沉积 喷气岩 金属矿床 成矿作用 

分 类 号：P618.205[天文地球—矿床学]