扬子地块西北缘、西南缘超大型卡林型金矿床的找矿方向

根据扬子地块西北缘、西南缘卡林型金矿床的地质、地球化学特征 ,可以将它们划分为三种矿床地球化学类型 :Au -As-(Sb)型、Au -Hg -(Tl或U)型和Au -Sb -黄铁矿型金矿床。Au -As-(Sb)型金矿床可以成为超大型金矿床。Au -As-(Sb)型金矿床的含矿建造富含有机质、沉积成因的黄铁矿和Au、As、Sb、Fe、S等。它们属于还原环境形成的黑色沉积岩系。其构造背景是被动大陆边缘的裂谷带和裂陷沉降盆地。Au -As-(Sb)型金矿床含矿建造的干酪根是Ⅱ型干酪根 ,其原始有机母质是还原环境中形成的海相菌藻类生物演化成的腐泥型有机质。大型或超大型金矿的干酪根的元素组成显示 ,含矿流体的脱碳作用和内生氧化作用在成矿过程中具重要意义。

METALLOGENIC PROGNOSIS OF SUPERLARGE CARLIN-TYPE GOLD DEPOSITS AT THE NORTHWEST AND SOUTHWEST MARGINS OF YANGTZE PLATE

Based on geological and geochemical characteristics of the Carlinr\|type gold deposits at the northwest and southwest margins of the Yangtze plate, they can be divided into three geochemical types: Aur\|Asr\|(Sb) type, Aur\|Hgr\|(Tl or U) type and Aur\|Sbr\|pyrite type. The Aur\|Asr\|(Sb)r\|type gold deposits may become superlarge ones. Orer\|bearing formations of the Aur\|Asr\|(Sb)r\|type gold deposits are rich in organic matter and sedimentary pyrite, as well as Au, As, Sb, Fe, S and so on. They belong to the black sedimentary rocks formed in a reducing environment. The geotectonic setting of orer\|bearing formations was inferred to be a rift belt and a downwarping basin of passive continental margin. Kerogen in the orer\|bearing formations of the Aur\|Asr\|(Sb)r\|type gold deposits is of Type Ⅱ, its original organic matter is sapropelic matter evolved from bacteria and algae formed in a reducing environment. Element composition of kerogen in the superlarge or great Carlin\|type gold deposits shows that decarbonization and endogenic oxidation of ore fluids must have taken place in the metallogenic process.