铜陵舒家店岩体的年代学和地球化学特征研究

摘要

舒家店岩体位于长江中下游中部的铜陵断隆区与繁昌断凹区(盆地)的过渡部位,主要的岩石类型有辉石闪长岩、石英闪长玢岩、花岗闪长斑岩、闪长岩以及闪长玢岩.本文通过对岩体中主要岩性-辉石闪长岩锆石LA-ICP MS精确定年、地球化学组成以及Pb同位索的分析,研究舒家店岩体的年代学、岩浆源区、岩浆演化和构造背景等问题.研究显示,舒家店岩体的侵入时间为139.2±2.1 Ma(MSWD=2.3,n=12),其活动时代同属于铜陵矿集区岩浆岩活动期,而不属于繁昌火山岩盆地.辉石闪长岩属于高钾钙碱性系列侵入岩,源区可能为接近于EMⅡ型富集地幔的交代地幔,岩浆演化的过程中,存在磷灰石、角闪石、辉石、榍石等矿物的结晶分异作用,同时还受到地壳物质的混染作用,是在挤压的构造背景下形成的.%The Shujiadian intrusion is located in the transition part between the Tongling faulting uplift and the Fanchang faulting basin in the Middle-Lower reaches of the Yangtze River. The rock types of this intrusion include pyroxene diorite, quartz diorite porphyrite, granodiorite porphyry, diorite and diorite porphyrite. This paper studied LA-ICPMS U-Pb dating data of the zircons from pyroxene diorite, and its geochemical compositions and Pb isotope, so as to probe the geochronology, source and evolution of magmas, and tectonic setting of the Shujiadian intrusion. The results indicate that the age of the Shujiadian intrusion is 139.2 ± 2.1Ma (MSWD＝ 2. 3, n＝ 12), suggesting that it is part of the magmatic system in the Tongling area, but not the Fanchang volcanic basin. Pyroxene diorite belongs to high potassium series. And the Shujiadian intrusion might derive from the metasomatic enriched mantle (EMⅡ). There existed crystal fractionation of minerals such as apatite, amphibole, pyroxene and plagioclase, which also affected by the assimlation of crust materials during the evolution of the magmas. The intrusion formed in a compressional regime.