贵州晴隆锑矿古油藏发现及其对锑矿成矿的约束研究

Qinglong antimony deposit is a classic one of Sb ore belt in South China, although being with a complicated geological tectonic background and a great disputation on ore genesis. But recently, a paleo reservoir is drilled by five holes with average thickness of 8.58m and average volume of 4.68% pitch in basaltic volcanic breccias and volcanic tuff of Dachang Strata where Sb orebodies usually occur in continued resources exploration activities directed by applicant in Shaziling section of Qinglong antimony deposit. Some sulfide minerals such as pyrite, stibnite, chalcopyrite and bornite are found coexisting with asphalt，and Sb ore bodies are also found under the asphalt layers. These findings above may indicate there may be close relation between ore forming and hydrocarbon accumulation. Based on investigation of ore geology, petroleum geology, inorganic geochemistry , organic geochemistry and　so　on, spatial, material and geochronologic relationship between Sb deposit and paleo-oil pool which is found lately will be analyzed in this applied project. Combing with new understandings of regional geology and geophysics generated in 2000s by Sinopec and other researchers, we will study coupling relationship between ore forming and evolution of Nanpanjiang-Youjiang sedimentary basin. Using this study data and previous study of other's achievements, we will also discuss basin-scale source of mineralization material and ore fluid, fluid pathways and mechanisms of ore forming, and then rebuild solid model of mineralization and　exploration　of　Qinglong antimony deposit. The disvovery of paleo-oil pool and the study of ore forming and hydrocarbon accumulation will provide weight of evidence in ore genesis of Qinglong antimony deposit, accelerating antimony and shale gas exploration in Southwestern Guizhou Depression. It is also helpful for enriching mineralization theory and intensive study of ore deposits in sedimentary basin, especially in study of organic matter effects on ore mineralization.

晴隆锑矿床是华南锑矿带典型矿床之一，但地质构造复杂，矿床成因争议较大。申请者负责的晴隆锑矿外围锑矿勘查项目，在锑矿赋存层位-"大厂层"中发现了古油藏，同时在沥青层之下也发现了锑矿层，说明晴隆锑矿床的形成与油气藏形成可能存在成生关系。本申请通过对晴隆锑矿及新发现的古油藏开展地质地球化学研究，探讨锑矿与古油藏的空间关系、物质关系和时间关系。结合晴隆锑矿床、区域地质和区域地球物理的最新研究成果，将锑矿床研究与南盘江-右江沉积盆地的演化相结合，在盆地尺度上探讨晴隆锑矿成矿物质和成矿流体来源、运移路径及成矿机理,构建锑矿床实体成矿模型。该研究不仅为锑矿床成因研究提供有力证据，将推动黔西南地区锑矿勘查和页岩气勘探。丰富和发展沉积盆地金属矿床成矿理论。

晴隆锑矿床是华南锑矿带内典型矿床之一，位于南盘江-右江盆地的黔西南坳陷。通过对晴隆锑矿及其附近的古油藏开展地质地球化学工作，得到如下认识。.成矿与成藏背景分析 通过区域构造分析、火山岩相分析和埋藏史分析，结合地球物理资料，查明晴隆锑矿床位于由青山镇主控断层、大厂古隆起和北东向二级断层构成的复式半地堑构造中。晴隆锑矿的成矿流体具有盆地流体性质。.古油藏的发现及地质特征 在锑矿勘查过程中，施工的5个钻孔发现合计15层沥青的古油藏，估算储量约36.84万吨。无论是在平面上还是在纵向上，古油藏与大厂锑矿都显示了密切的空间关系，推测两者的形成具有成生关系。.古油藏地球化学特征 根据有机元素分析，确定古油藏沥青为碳质沥青。测定的沥青反射率值对应的温度为199 ℃ ~ 211℃，平均为206℃，处于凝析油湿气阶段末期或干气阶段早期。沥青碳同位素为-27.7‰ ~ -28.8‰，平均为-28.1‰，接近泥盆系烃源岩。沥青微量元素特征显示Cu有一定的富集，Sb未富集。沥青稀土元素特征与辉锑矿的差异很大，推测成藏成矿流体不一致。古油藏流体包裹体均一温度为121.5℃~156.1℃，平均为136.8℃，低于晴隆锑矿流体包裹体均一温度，说明锑矿床的形成伴随着部分液态烃和凝析油-湿气的形成。.沥青来源及成因 根据饱和烃气相色质谱和稀土元素特征曲线，古油藏沥青来源于泥盆系烃源岩。.古油藏生油时代厘定 通过沥青Re-Os精确定年，测得约252 Ma年龄，通过沥青Re-Os同位素分馏原理，结合南盘江-右江盆地石油地质背景资料，认为该年龄代表了D烃源岩的生烃年龄。.古油藏与晴隆锑矿成矿关系 晴隆锑矿泥盆系烃源岩在晚二叠世初期（254.3 Ma）生油，伴随着埋藏作用的加深和印支运动的驱动，原油沿同生断层和不整合面运移至二叠系不整合面上下的玄武岩、大厂层和茅口灰岩有利空间中逐渐储存形成油藏，油藏成藏年代约235 Ma，并逐渐演化成古油气藏（含沥青、天然气等），气藏运移至大厂背斜核部进而促使锑矿发生硫酸盐热化学还原作用（TSR），向成矿流体提供大量的S2+，锑矿在燕山中晚期（142~148Ma）成矿。硫同位素显示古油藏沥青与晴隆锑矿具有相同硫源。