青海格尔木地区驼路沟钴(金)矿床石英钠长石岩锆石SHRIMP U-Pb定年——对“纳赤台群”时代的制约

SHRIMP zircon U-Pb dating of quartz albitite from the Tuolugou cobalt (gold) deposit, Golmud, Qinghai, China-Constraints on the age of the Naij Tal Group.

青海格尔木驼路沟矿区赋矿火山-沉积岩系中的石英钠长石岩样品锆石SHRIMPU-Pb精细测年结果表明,该岩石具有一组8个测点构成的455～483Ma的206Pb/238U年龄数据,加权平均年龄为468Ma±9Ma,应代表本区海底火山喷流作用的时间,因此重新厘定了矿区内含矿岩系的时代为奥陶纪,同时,这一年龄指示区域上纳赤台群主体的时代应为早古生代。其他较老年龄锆石是由强烈的海底火山喷发作用从深部基底物质中带出的,并与热水流体一起沉积下来,赋存在石英钠长石岩中。锆石年龄多组性表明了本区基底演化和源区物质的复杂性。

This paper reports the results of highly precise zircon SHRIMP U-Pb dating of quartz albitite in the volcanic-sedimentary series of the Tuolugou cobalt (gold) deposit, Golmud, Qinghai. Analyses of eight spots presented 206Pb/238U ages of 455 to 483 Ma with a weighted mean age of 468±9 Ma, which represents the timing of submarine volcanic exhalation in this area. Therefore, the age of the host rocks of the Tuolugou ore district is redefined as Ordovician, which implies that regionally the main part of the Naij Tal Group should be Early Paleozoic in age. Some other older zircons with 206Pb/238U ages of 932 to 2443 Ma were brought from Precambrian basement rocks at depth by strong submarine volcanic eruption and then deposited in quartz albitite together with hydrothermal fluids. The wide range of ages of older zircon reflects the complex tectonic evolution of the basement in the area and multi-source material.