玻利维亚Laurani斑岩-浅成低温热液矿床地质特征及控矿因素

Laurani矿床是玻利维亚Altiplano盆地内典型的高硫化浅成低温热液矿床,发现和开采历史悠久,但研究程度低,控矿因素和找矿潜力不清.通过矿床地质特征精细解剖,文章查明了该矿床控矿因素,分析了深部找矿潜力.研究表明,构造-岩浆作用为其主导性控矿因素.火山穹窿构造与环状断裂约束了矿床的定位,侵入接触构造、爆破角砾岩...

Geological characteristics and ore-controlling factors of Laurani porphyryepithermal deposit, Bolivia

Laurani deposit is a typical high-sulfidation epithermal deposit in the Altiplano basin, Bolivia. The deposit has a long history of discovery and exploitation, but the research degree is low, and its ore-controlling factors and prospecting potential are still unclear. Through detailed analysis on geological characteristics of the deposit, we summarized ore-controlling factors and provided insight into prospecting potential of the Laurani deposit. Tectonism and magmatism are the dominate ore-controlling factors. The volcanic dome and ring faults constrain the location of the deposit. The intrusion contact zones, explosive breccia pipes, NE-trending faults and fractures control the formation and distribution of ore-bodies(-veins). The igneous rocks comprise monzogranite porphyries,dacites, dacite porphyries and tuffs, belong to high-K calc-alkaline and shoshonite series, and have a relatively consistent zircon U-Pb ages(~7.5 Ma), which indicates they are the products of the same magmatic event in the late Miocene. The Laurani deposit develops four types of mineralization with different occurrence characteristics: Porphyry-type Au-Cu, explosive breccia-type Au-Cu, contact-type Cu-Au-Ag and hydrothermal vein-type Au-Ag-Cu-Pb-Zn. There is a clear element zonation, horizontally the Au-Ag-Cu-Pb-Zn and Ag-Pb-Zn occur respectively in hanging wall and footwall of the Huari Humana fault;vertically the Au-Cu forms mainly in the deep part and Au-Ag-Cu-Pb-Zn develops well in the shallow part. The Laurani deposit has extensive hydrothermal alterations with significant zonation. Centered with dacite porphyries, the horizontal zoning of alteration varies outwards from phyllic to propylitic and carbonate alteration. Widespread argillic alteration overprints on the phyllic and propylitic zones to varying degrees in the shallow. Quartz-alunite-barite distribute mainly within the hydrothermal vein-type ore-bodies and their adjacent areas. Vertically, the alteration zoning varies from phyllic to propylitic and argillic from the deep to the shallow. The absence of the potassic zone in the Laurani deposit, is likely due to its possible existence in deep and has not been exposed. The deposit is well preserved resulted from weak post-mineral tectonism, combined with the interception of porphyry-type and explosive breccia-type mineralization in the deep by drilling, we suggest there is great upside potential for porphyry-type ore-bodies in the deep of the Laurani deposit.