滇中姚安老街子板内富碱火山岩锆石SHRIMP U-Pb年代学及火山机构划分

发布时间：2018-07-21 16:20

【摘要】：滇中姚安老街子板内富碱火山-岩浆杂岩体属于哀牢山-金沙江富碱侵入岩带的一部分,因其富含Pb-Ag-Au多金属矿床和特殊大地构造位置被地质学家广泛关注。尽管前人在矿床学(金属赋存状态和物质来源)、岩石学、地球化学等方面展开大量的研究,但关于姚安富碱火山岩体火山机构和岩相学以及形成时代等却少有研究。本文对老街子火山-岩浆杂岩体进行详细的岩相学地质调查和剖面实测,划分出完整的次火山岩相(含集块正长斑岩)、火山-沉积相(凝灰质砾岩和砂岩)和火山喷发相火山机构,其中将火山喷发相细分为溢流亚相(熔结凝灰岩和假白榴石粗面岩)和爆发亚相(含角砾和集块粗面质熔结凝灰岩)。并对粗面质凝灰岩和熔结凝灰岩进行锆石SHRIMP U-Pb精确年代学研究,最终分别获得~(206)Pb/~(238)U年龄加权平均值为33.63±0.50Ma和33.27±0.38Ma,代表着火山岩喷发形成时代为渐新世。该期火山岩的报道为老街子Pb-Ag-Au矿区深部外围找矿预测提供新思路,也为青藏高原东南缘新生代岩石圈构造演化和地球动力学过程研究提供新的窗口。
[Abstract]:The alkali-rich volcanic-magmatic complex of Laojie sub-plate in central Yunnan is a part of the Ailaoshan-Jinshajiang alkali-rich intrusive rock belt, and has been widely concerned by geologists for its rich Pb-Ag-Au polymetallic deposits and special geotectonic locations. Although many previous studies have been carried out in ore deposit (state of occurrence and source of metals) petrology and geochemistry few studies have been carried out on volcanic mechanism petrography and age of formation of the Yao'an alkali-rich volcanic rock body. In this paper, detailed petrographic geological investigation and profile measurement of Laojie volcano-magmatic complex are carried out. The subvolcanic facies (containing syenite porphyry), the volcanic-sedimentary facies (tuffaceous conglomerate and sandstone) and the volcanic mechanism of volcanic eruption facies are distinguished. The volcanic eruption facies are subdivided into overflow subfacies (melt-bound tuff and pseudo-garnet trachyte) and explosive subfacies (breccia and agglomerate melt-deposited tuff). Zircon shrimp U-Pb dating of coarse surface tuff and fused tuff is carried out, and the weighted mean values of ~ (206) Pb / 238 U age are 33.63 卤0.50 Ma and 33.27 卤0.38 Ma, respectively, indicating that the volcanic eruption occurred in the Oligocene epoch. The report of volcanic rocks in this period provides a new idea for the prospecting and prediction of the deep periphery of the Pb-Ag-Au mining area in Laojie Zi, and also provides a new window for the study of the Cenozoic lithospheric tectonic evolution and geodynamic processes in the southeast margin of the Qinghai-Tibet Plateau.
【作者单位】：昆明理工大学国土资源工程学院地球科学系;中国地质科学院地质研究所北京离子探针中心;
【基金】：北京离子探针中心开放基金(编号:DDC15-016) 云南省应用基础研究计划青年(编号:2016DF031) 国家重点基础研究发展计划(编号:2015CB452600、2015CB452605)项目联合资助的成果
【分类号】：P588.14;P597.3

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