三江地区中段成矿元素地史演化的探讨及意义

DISCUSSIONS ON THE GEOLOGIC EVOLUTION OF MINERALIZING ELEMENTS IN THE MIDDLE PART OF THE THREE-RIVER AREA AND ITS SIGNIFICANCE

以富集系数值 ( ki)为指标 ,系统讨论了三江地区中段 Au,Ag,Cu,Pb,Zn,As,Sb,Hg8个成矿元素从老基底时期—盖层时期—古特提斯时期—中新生代地层时期富集与贫化的演化历史情况。研究表明 ,基底时期 Cu-Pb-Sb富集 ;盖层时期 Au-Ag富集 ,特别是 As强烈富集 ;古特提斯洋时期 ,Au-Sb强烈富集在金沙江洋脊环境 ,Cu强烈富集在金沙江洋岛环境 ;古特提斯弧时期 ,金沙江洋内弧表现出 Cu的富集 ,Pb-Zn富集在滞后弧 ,而碰撞弧及澜沧江陆缘弧没有成矿元素的明显富集 ;中新生代时期 ,As-Hg富集。

Based on the indexes of the enrichment coefficients( k i )of eight mineralizing elements,i e Au,Ag,Cu,Pb,Zn,As,Sb and Hg,their geologic evolution of enrichment and depletion is systematically discussed from the basement to the cover,to Paleo Tethys,and to Mesozoic Cenozoic time.It is shown that the elements of Cu,Pb and Sb are enriched in the old basement;and the cover strata are enriched in Au,Ag,especially in As.In the Paleo Tethyan ocean period,Au and Sb were strongly enriched in the Jinsha River mid ocean ridge setting,and Cu was evidently enriched in the Jinsha River oceanic island setting.In the Paleo Tethyan arc period,Cu was enriched in the oceanic island arc,and Pb and Zn were enriched in the post collisional arc('delay'arc).The collisional arc and Lancang River continental marginal arc were not rich in the mineralizing elements.As and Hg were enriched in the Mesozoic and Cenozoic period.