滇西北休瓦促钨钼矿区复式岩体地质及其成矿特征——来自年代学、氧逸度和地球化学的约束

发布时间：2018-06-16 12:53

本文选题：休瓦促 + W-Mo矿床　；参考：《岩石学报》2017年07期

【摘要】：休瓦促钨钼矿床位于义敦岛弧南段的香格里拉北部,目前已达中-大型。该区发育由两期岩体(晚三叠世的黑云母花岗岩和晚白垩世的斑状二长花岗岩)叠加而成的复式岩体,而该矿区钨钼矿形成于82~86Ma。然而,两期岩体间关系,以及晚三叠世岩体对矿床的形成有怎样的贡献,目前未有报道。笔者通过对两期岩体形成时间及其地球化学特征的研究,从成岩年代学、岩浆氧逸度等方面探究上述问题,并揭示两期岩体的成矿特征,为找矿实践提供一定的参考依据。研究表明,黑云母花岗岩结晶年龄为211.7±2.6Ma,SiO_2偏高(69.48%~73.73%),属高钾的钾玄质系列,偏铝质,富集轻稀土元素和大离子亲石元素而亏损重稀土元素以及高场强元素Nb、Sr、Ti等,有微弱的负Eu异常,岩浆氧逸度相对较高(fO_2=-19.4~-9.1,平均-13.7);斑状二长花岗岩结晶年龄为76.8±3.8Ma,且有一颗锆石核部的年龄值为219±2.6Ma,该岩体与前者有相似的地球化学特征,SiO_2高(67.35%~75.65%),属偏铝质的钾玄质系列,ΣREE较高,高于黑云母花岗岩,铕负异常明显大于前者,岩浆氧逸度相对较低(fO_2=-30.4~-18.2,平均-23.4)。据此,结合休瓦促矿区断层发育情况,提出矿区内两期岩体以近南北向F_4为界呈断层接触关系,北西向走滑断层(F_1-F_3)为控矿构造。本文认为,晚期斑状二长花岗岩对早期黑云母花岗岩具有一定的继承性关系,黑云母花岗岩来源于晚三叠世甘孜-理塘洋向西俯冲环境下地壳的部分熔融,岩浆富水、氧逸度高,利于形成Cu-Au矿床,且在找矿实践中得到部分验证;斑状二长花岗岩来源于加厚下地壳的部分熔融,岩浆贫水、氧逸度低于黑云母花岗岩,与W-Mo矿床相关。即,晚白垩世岩浆热液沿矿区断裂-裂隙系统运移,继承和发展早期岩浆活动,形成脉状细晶岩和W-Mo矿床。
[Abstract]:The Huva-promoted tungsten and molybdenum deposit is located in the northern Shangri-La in the southern segment of Yidun Island Arc. A complex rock mass consisting of two stages of rock mass (late Triassic biotite granite and late Cretaceous porphyry monzomorphic granite) was developed in this area, while the tungsten and molybdenum deposit in this area was formed at 82 ~ 86 Ma. However, the relationship between the two stages and the contribution of the late Triassic rock mass to the formation of the deposit have not been reported. Based on the study of the formation time and geochemical characteristics of the two stages of rock mass, this paper probes into the above problems from the aspects of diagenetic chronology and magmatic oxygen fugacity, and reveals the metallogenic characteristics of the two periods of rock mass, which provides a certain reference basis for prospecting practice. The results show that the crystallization age of biotite granites is 211.7 卤2.6MaSiO-2, which is 69.48g / 73.73g, belongs to the potassium metamorphic series with high potassium, aluminite, enriched light rare earth elements and large ion lithophile elements, and depleted heavy rare earth elements and high field strength elements, such as NB, SrTi, and so on. There are weak negative EU anomalies, such as negative EU anomalies, weak negative EU anomalies, and weak negative EU anomalies, due to the enrichment of light rare earth elements and large ion lithophiles. The oxygen fugacity of magma is relatively high, with an average of -13.70.The crystallization age of porphyry monzonitic granites is 76.8 卤3.8 Ma.The age of one zircon core is 219 卤2.6 Ma.The body has a similar geochemical characteristic to the former, SiO2 is high 67.3575.650.It belongs to the potassium metaluminite series, and 危 REE is higher. Compared with the biotite granite, the negative anomaly of europium is obviously greater than that of the former, and the oxygen fugacity of the magma is relatively low. The oxygen fugacity of the magma is relatively lower than that of the biotite granite. On the basis of this, combined with the fault development in Xiuwa mining area, it is proposed that the fault contact relation between the two stages of rock mass in the mining area is near north-south direction FSP _ 4, and the north-west strike-slip fault (F1-F _ 3) is the ore-controlling structure. It is believed that the late porphyry monzogranites have a certain inheritance relationship to the early biotite granites. The biotite granites originated from the partial melting of the crust in the late Triassic Ganzi-Litang oceanic subduction environment, and the magma is rich in water. High oxygen fugacity is favorable for the formation of Cu-Au deposit and is partly verified in prospecting practice. Porphyry monzonitic granites are derived from partial melting of thickened lower crust, magma is poor in water, and oxygen fugacity is lower than biotite granite, which is related to W-Mo deposit. That is the late Cretaceous magmatic hydrothermal fluid migrated along the fault-fissure system of the mining area inherited and developed the early magmatic activities and formed vein-like fine-grained rocks and W-Mo deposits.
【作者单位】：中国地质大学地球科学与资源学院;云南省地质调查局;中国地质调查局成都地质调查中心;中国地质大学地质过程与矿产资源国家重点实验室;
【基金】：国家重点基础研究发展计划项目(2015CB452605) 云南省科技领军人才培养计划项目(2013HA001)联合资助
【分类号】：P618.6

【参考文献】