摘要
呷村矿床是一个与晚三叠世海相钙碱性酸性火山岩系有关的典型块状硫化物（ＶＨＭＳ）矿床。热水流体系统和贱金属成矿作用发育于义敦岛弧碰撞造山带上的弧间裂谷盆地内，并受其内部的一系列局限盆地及ＳＮ向基底断裂－裂隙系统控制。含矿岩系为双峰岩石组合，具火山碎屑岩－矿体－喷气岩“三位一体”特征。硫化物矿床具有“块状矿席＋层控网脉状矿带”式三维结构特征。块状矿席发育多旋回的硫化物－硫酸盐韵律型式，揭示热水流体在海底的幕式排泄以及硫化物－硫酸盐在卤水池内的韵律式化学淀积和滑塌堆积过程。层控网脉状矿带产出于流纹质火山岩系，与上覆的块状矿席平行展布，揭示高渗透性碎屑岩层和多条同级别断层或断裂共同约束海底下部热水流体，并诱导其“弥散式”排泄和侧向流动交代。热水流体的传导冷凝过程导致硫化物沉积，热水流体与冷海水的简单混合导致硅质岩或／和重晶石淀积，传导冷凝与海水混合的联合作用导致含硫化物重晶石、硅质岩和红碧玉形成。
The Gacun deposit is a typical massive sulfide deposit associated with Late Triassic seafloor calc-alkaline felsic volcanics (VHMS). The hydrothermal fluid system and base metallic mineralization were developed in interarc rift basins of Yidun arc-collision orogenic belt. The emplacement of orebodies was controlled by a series of restricted basins and SN-trending fault-fissure systems. The ore-bearing beds have a bimodal rock association and exhibit assembly characteristics of pyroclastic rock, orebody and exhalite. The sulfide deposits have three- dimensional texture feature of 'massive ore sheet plus stratabound network ore zone'. Massive ore sheets show polycyclic rhythmicity of sulfide + sulphate, suggesting that the hydrothermal fluids were discharged episodically on seafloor, and sulfides and sulphate were both deposited chemically in brine pools and accumulated through collapse. The stratabound network ore zones occur in rhyolitic volcanics and are distributed in parallel with the massive ore sheets, indicating that the highly-permeable clastic rock and several same-order faults jointly controlled the hydrothermal fluid systems beneath the seafloor and caused diffused discharge and lateral metasomatism of ore-bearing fluids. Conduction cooling of ore-bearing fluids led to sulfide deposition; meanwhile simple mixing of hydrothermal fluid and cool seawater resulted in formation of silicate and barite rocks. The combined action of conduction cooling and seawater mixing would cause deposition of sulfide-bearing barite, silicate and jasper rocks.
出处
《矿床地质》
CAS
CSCD
北大核心
2001年第1期44-56,共13页
Mineral Deposits
基金
国家自然科学基金项目(49773177)
国家科技部流体攀登项目(95-预-39)联合资助
