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。
The Laojiezi alkali-rich volcano-magmatic complex in Yao’an, Central Yunnan province, is part of the Cenozoic Jinsha River-Ailaoshan alkali-rich intrusive rock zone. It has been widely concerned by the geologists because it hosts a large amount of Pb-Ag-Au polymetallic deposits and is special intraplate tectonic location. Although the previous researchers mainly concentrated on the mineral deposits with main study of metal state and material sources, petrology and geochemistry etc, there are few studies on the volcanic edifice. This study carried out an investigation over the alkali-rich volcanic rocks in Yao’an using petrography and profile measurement. One complete volcanic edifice is divided： subvolcanic facies （orthophyre contained agglomerates）, volcanic sedimentary facies （tuffaceous conglomerate and sandstone）, and volcanic eruption facies. Among them, the volcanic eruption facies are subdivided into the effusion subfacies （ignimbrite and pseudoleucite trachyte） and the explosive subfacies （trachytic ignimbrite contained breccia and agglomerates）. Zircon SHRIMP U Pb dating was also conducted for the Laojiezi rich alkali trachytic tuff and ignimbrite, yielding two 206Pb/238U weighted average ages of 3363±050Ma and 3327±038Ma. This indicates that the volcanic eruption age occurred in the Oligocence. The report of this period volcanic rock in the Sanjiang orogenic zone provides not only a new idea for ore prediction in deep and peripheral of the Laojiezi Pb Ag Au polymetallic deposit, but also a new window for Cenozoic lithospheric tectonic evolution and the geodynamics process in the southeastern margin of the Qinghai Tibet Plateau.
作者
严清高
江小均
吴鹏
孙会一
管申进
YAN Qinggao JIANG Xiaojun WU Peng SUN Huiyi GUAN Shenjin(Department of Earth Sciences, Faculty of Land Resource Engineering, Kunming University of Science and Technology ,Kunming, 650093 ,China Beijing SHRIMP Center, Institute of geology, Chinese Academy of Geological Sciences, Beijing , 10037, China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2017年第8期1743-1759,共17页
Acta Geologica Sinica
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
关键词
滇中
老街子
富碱火山岩
SHRIMP
U-PB年代学
火山机构
Central Yunnan Province
Laojiezi
alkali-rich volcanic rocks
SHRIMP U-Pbgeochronology
volcanic edifice
