新元古代陆缘岩浆弧——塔里木盆地巴楚隆起的基底:来自钻井岩芯的最新证据

塔里木盆地巴楚隆起西缘的同1井(TX1)在寒武系之下钻遇一套火山岩,本文对该套火山岩的岩石类型、形成时代、岩石成因及构造环境进行了详细研究。结果显示,这套火山岩可分为上下两段,分别为杏仁状辉石安山岩和角闪石英安岩,属于钙碱性系列火山岩,形成于大陆边缘弧构造环境。安山岩锆石U-Pb年龄(747±12Ma)表明该岩浆弧发育时代为新元古代。同1井钻揭的火山岩与卡塔克隆起上塔参1井(TC1)钻揭的闪长岩(744.0±9.3Ma~790.0±22.1Ma)和花岗闪长岩(757.4±6.2Ma)成岩时代一致、形成环境相同,表明横亘塔里木盆地中部的古隆起带(巴楚隆起-卡塔克隆起-古城虚隆起)起源于一条新元古代陆缘岩浆弧,塔里木盆地的基底是由新元古代造山作用拼合的基底。以中央隆起带为界,南、北塔里木的基底性质和成盆演化过程可能有所差异。

Bachu uplift in the central Tarim Basin based on Neoproterozoic continental arc: New lines of evidence from drilled andesite and dacite

A set of volcanic rocks was drilled beneath the Cambrian in TX1 well on the western margin of the Bachu uplift in the Tarim Basin, the rock type, diagenetic age, petrogenesis and tectonic setting of the volcanic rocks were systematically analyzed in this paper. The results show that two sections of the volcanic rocks are almond-shaped pyroxene andesite and hornblende dacite respectively, belonging to the calc-alkaline series and formed in a continental margin arc tectonic setting. SIMS U-Pb isotopic dating on zircons from the andesite obtained a weighted average age of 747±12Ma, indicates that the magmatic arc developed in the Neoproterozoic. The volcanic rocks drilled by TX1 well coincide with the diagenetic age and tectonic setting of diorites (744.0±9.3Ma~790.0±22.1Ma) and granodiorites (757.4±6.2Ma) drilled by TC1 well in Katake uplift, suggests that the paleo-tectonic uplift (Bachu uplift-Katake uplift-Guchengxu uplift) running through the central of the Tarim Basin originated from a Neoproterozoic continental margin magmatic arc. The basement of the Tarim Basin is a amalgamated basement formed in the Neoproterozoic orogeny. With the central uplift belt as the boundary, the basement and basin evolution may differ between the northern and southern Tarim.