伊犁地区果子沟南华系塔里萨依组冰碛岩顶部花岗斑岩年龄及其意义

Granite Porphyry SHRIMP U-Pb Age at Top of the Nanhuan Talisaye Formation in Guozigou,Ili area,and Implications for Glaciogenic Diamictite

西天山东北段伊犁地区的果子沟—科古琴剖面发育了新元古代3套冰碛岩,自下而上为库鲁铁列克提组(下冰碛岩)、别西巴斯套组(中冰碛岩)和塔里萨依组(上冰碛岩)。前人研究认为塔里萨依组冰碛岩与库鲁克塔格地区的汉格尔乔克组对比。本文报道了侵入于塔里萨依组顶部的花岗斑岩中岩浆锆石206Pb/238U年龄为(642±5)M a,应代表花岗斑岩的形成时代。尽管该年龄为花岗斑岩侵位年龄,但可限定果子沟剖面塔里萨依组冰碛岩的沉积上限。由于区内有库鲁铁列克提组(下冰碛岩)和别西巴斯套组(中冰碛岩),可分别对比于库鲁克塔格地区的贝义西组和阿勒通沟组冰碛岩,故推测塔里萨依组冰碛岩应与特瑞艾肯组冰碛岩对比而不是前人认为的与库鲁克塔格地区汉格尔乔克冰碛岩对比。所以,本文为西天山果子沟剖面新元古代冰期地层的时代划分及其与库鲁克塔格地区的对比提供了新的证据。

There are three diamictite（tillite） units in the Guozigou—Keguqin section in Ili area of the northern part of the Western Tianshan Mountains,which are Qurutielikti Formation（Lower diamictite）,Biexibasitao Formation（Middle diamictite） and Talisaye Formation（Upper diamictite） from bottom to top.According to the former study,the Talisaye Formation is still correlated with the Hagriqaok diamictite in Quruqtagh area.This paper reports a magmatic zircon age of 642±5 Ma（206Pb/238U） from granite-porphyry,which intrudes into the top of the Talisaye Formation.This dating represents the evolved magma age.Even this is the dating of the intrusive body,yet this is a new evidence for the up limit of the Talisaye Formation.Meanwhile,the Qulutielikti Formation（Lower diamictite）,the Biexibasitao Formation（Middle diamictite） correlated with Bayxi diamictite and Alatonggou diamictite respectively in Quruqtagh area,so we can put a suggestion that the Talisaye diamictite is correlated with Teruiaiken diamictite and not with Hagriqaok diamictite in Quruqtagh area.So,this paper advanced a new evidence for the Neoproterozoic glaciogenic diamictite between the Guozigou section in the Western Tianshan and some sections in Quruqtagh area in the Eastern Tianshan.