川西九龙花椒坪燕山期花岗岩的厘定及其地质意义

    Determination of Yanshanian Granite and its Geological Significance in the Taka Dome, Western Sichuan

    • 摘要: 这是一篇地球科学领域的论文。川西九龙是目前燕山期花岗岩分布最为集中的地区,有铁厂河、桥棚子-烂碉及新火山岩体。踏卡穹隆外围花椒坪分布有约0.5 km2的花岗岩岩株,本文通过对该花岗岩开展LA-ICP-MS锆石U-Pb年代学研究,以确定该花岗岩的形成时代及其与周边花岗岩的时空联系,为松潘-甘孜南缘里伍式铜矿的对比研究提供依据。结果显示,花椒坪花岗岩成岩年龄为(163.1±1.4) Ma,该岩体遭受了晚期(146±3) Ma的岩浆作用或构造热事件改造,与周边铁厂河、新火山、洛莫地区花岗岩体经历的地质事件一致。花椒坪花岗岩浆温度为592~727 ℃(平均温度648 ℃),明显低于桥棚子花岗岩浆温度(766~804 ℃),为低温花岗岩。结合区域地质背景,170~140 Ma,松潘—甘孜地块南缘岩石圈处于伸展阶段,早期(163 Ma)以花椒坪为主体的花岗岩浆活动,晚期(146 Ma)遭受了岩浆作用或构造热事件的改造。这一发现丰富了九龙地区燕山期岩浆或构造-热事件。

       

      Abstract: This is an article in the field of earth sciences. Jiulong area is the most concentrated area of Yanshanian granite found in western Sichuan, including Tiechanghe, Qiaopengzi-Landiao and Xinhuoshangranite. In this paper, LA-ICP-MS zircon U-Pb dating were carried out to determine the formation age of the granite, and its temporal-spatial relationship with the surrounding granites, providing a basis for the comparative study of Liwu copper deposit in the southern margin of Songpan-Ganzi block. The results show thatthe diagenetic age of Huajiaoping granite is (163.1±1.4) Ma, andit underwent magmatic or tectonic thermal events at (146±3) Ma, which is consistent withthe geological events ofTiechanghe, Xinhuoshan and Luomogranite. The magma temperature of Huajiaoping granite is 592~727 ℃ (average temperature 648 ℃), which is significantly lower than that of Qiaopengzi granite (766~804 ℃). Combined with the regional geological background, about 170 ~ 140 Ma, the lithosphere in the southern margin of Songpan Ganzi block is in the extension stage. The granite magma activity dominated in the early stage (163 Ma) by Huajiaoping granite, and in the late stage (146 Ma) by magmatism or tectonic thermal events. This discovery enriched the Yanshannian granitic magmatic thermal events in Jiulong area.

       

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