黔西南灰家堡金矿田成矿构造模式及构造地球化学研究

通过解析灰家堡金矿田地质和地球物理等资料,建立该矿田成矿构造模式,并应用构造地球化学研究方法了解Au和其他微量元素在不同构造部位分布情况,最后将研究结果应用于找矿勘探实践。灰家堡背斜是龙潭组及其之上地层由弯滑褶皱作用形成的。背斜中Au元素在垂向上主要沿着构造蚀变体和背斜轴分布,在横向上背斜核部越紧闭金矿化越强,显示了明显的背斜控矿特征。微量元素因子分析显示成矿元素组合为Au、As、Sb、Hg和Tl。对应分析表明构造蚀变体中的角砾岩主要富集Sb和Tl,龙潭组和长兴组的生物碎屑灰岩主要富集Au,龙潭组的黏土岩、粉砂质黏土岩等主要富集Hg和As。原生晕垂向分带序列自下而上为Tl-Sb-Hg-Au-As。在综合成矿构造模式和构造地球化学研究的基础上,认为黔西南二叠系-三叠系浅海碳酸盐台地相区的背斜/穹窿及相关的逆断层构造组合区是重要的找矿区域,Au、As、Sb、Hg和Tl元素异常套合最好的地段为找Au有利靶区,高As/Tl比值地段深部找矿潜力大,且碳酸盐岩和黏土岩组合部位是有利的富Au部位。

Tectonic Model and Tectonic-geochemistry Characteristics of the Huijiabao Gold Orefield,SW Guizhou Province

TheHuijiabao gold orefield is located at the border of Xingren and Zhenfeng counties, southwestern Guizhou province. Sedimentary rocks in the gold orefield consist of bioclastic limestone, siltstone, and argillite, which are Middle and Upper Permian and Lower Triassic in age. The Upper Permian and its overlying strata were deformed into an East–West-trending anticline with limbs cut by reverse faults. A series of Northeast-striking faults cut the major reverse faults, some of which control the mercury–thallium deposits/occurrences. In this paper, we established the tectonic model of the Huijiabao gold orefield based on geology and geophysics, determined the spatial distribution of gold and other trace elements, and proposed geological prospecting direction at the southwestern Guizhou province. Folding of the Upper Permian and its overlying strata caused the horizontal shortening and vertical thickening. Displacement differential of these strata at different parts of the anticline led to tear which cuts the anticline into several blocks. Blocks with closed anticline show strong gold mineralization, whereas blocks with gentle anticline display weak gold mineralization. Gold mainly distributes along the anticlinal axis and the unconformity between the Middle and Upper Permian on a representative profile. Factor analysis of trace elements shows that ore-forming elements consist of Au, As, Sb, Hg and Tl, which are important prospecting indicator elements. Other trace elements have no obvious relation with gold mineralization. Correspondence analysis between elements and rocks/strata shows that the unconformity is enriched in Sb and Tl, the bioclastic limestone of the Longtan and Changxing Formations is enriched in Au, and the argillite of the Longtan Formation is enriched in Hg and As. The zonation of ore-forming elements is calculated to be Tl–Sb–Hg–Au–As (from bottom to top). We therefore propose that (1) zones near the anticline/dome and related reverse fault are important target areas, (2) element anomalies of Au, As, Sb, Hg and Tl are helpful prospecting indicators, (3) high As/Tl ratio may indicate concealed gold orebodies, and (4) locations of carbonate rock and argillite are favorable gold precipitation position.