铜陵舒家店地区岩浆活动系统动力学

The Tongling district with about 40km long in an E-W direction and 20km wide, which is situated in the eastern part of the Yangtze River Basin in Anhui Province, is an ancient copper capital of China and one of the most important metal-bearing districts. Within the district there are 76 intermediate-silicic intrusive bodies and 54 known ore deposits. The ore deposits are predominantly skarn-type with copper, iron and gold mineralization, accompanied by minor stratabound-type in the host carbonates. The total reserves in this district have been estimated to be 500Mt copper and 150t gold. Shujiadian is located at the middle of Tongling area. The intermediate-acid intrusive rocks in Shujiaduan, Tongling belong to shoshonitic and high-K calc-alkaline series. The shoshonitic series consist chiefly of pyroxene monzodiorite and quartz monzonite, while the high-K calc-alkaline series consist of quartz monzodiorite and granodiorite porphyry. Meanwhile, a lot of different lithological dikes occurred in the area, such as granite-porphyry, diorite-porphyrite, diabase and lamprophyre. All of them are the parts of the whole magmatism system in the area. The Shujiadian copper deposits mainly occur in the pyroxene monzodiorite body or near the Silurian siltstone. The copper deposites were regarded as a porphyry copper deposit. However, the copper deposits are not related to the granodiorite porphyry from the space relationship between the mineralization and the intrusive body. Which intrusive rock is related to the copper mineralization in the magatism system? Whether or not the copper deposit is porphry type? In addition, a 3000m scientific drilling in the area recently revealed a more than 700m thick synogranite below 1800m of the surface which is never seen in the whole Tongling area including Shujiadie area. What is the relationship between the synogranite and the intermediate-acid intrusive rocks? Which one is the contribution to the copper mineralization? Solving these problems is an important scientific significance on enriching the genesis dynamics of magmatic system and the mineralization theory, and is a practical significance on the deep prospecting in this area and the whole middle-lower reaches of the Yangtze River region. In conclusion, the proposal of this project aims to elaborate the genesis of the different sequences of intrusive rocks and the deep dynamics process of the magmatism, determine the relationship between the mineralization and which sequence of the intrusive rock, and provide the theoretical basis for the prediction of regional ore deposits based on the studies of petrology, geochemistry, mineralogy and mineral inclusions, in suit zircon U-Pb dating and Hf-O isotope, and Re-Os isotope of igneous rocks in Shujiadian area.

铜陵舒家店地区出露橄榄安粗岩系列的辉石二长闪长岩和石英二长岩、高钾钙碱性系列石英二长闪长岩和花岗岩长斑岩以及各种脉岩类，并伴随着铜矿化，所有这些都是区内中生代岩浆活动系统的一部分。舒家店铜矿主要产在辉石二长闪长岩体中,被认为是斑岩型铜矿，但从矿化与不同侵入岩体的空间关系上看，该铜矿与区内的花岗闪长斑岩并不相关。该铜矿究竟与哪一期侵入岩有关？该铜矿究竟是不是斑岩型铜矿？另外，作者负责的3000米科学钻近期揭示出舒家店地区1800以下存在700余米厚的正长花岗岩，这种岩石在整个铜陵地区的地表或一般钻孔中从未见到过，它与其它中酸性侵入岩有何成因联系？搞清这些问题，对于丰富岩浆系统成因动力学及其成矿作用的理论具有重要的科学意义，对区内仍至整个长江中下游地区深部找矿也具有重要的现实意义。

舒家店地区是铜陵矿集区重要的矿田之一。区内出露众多类型的侵入岩体，它们侵位的时序、成因如何？铜矿化究竟与哪一期侵入岩有关？铜陵地区3000米科学钻揭示出1775米深处以下存在700米厚的正长花岗岩，这种岩石在整个铜陵地区的地表或一般钻孔中从未见到过，它属何种成因类型？与其它侵入岩有何成因联系？本项目针对这些问题开展了研究。.本项目以铜陵舒家店地区野外露头、铜矿床勘探钻孔岩心和铜陵3000米科学钻岩心为研究对象，在详细的岩相学研究基础上，开展了锆石U-Pb年代学、矿物化学、岩石学、地球化学、锆石Lu-Hf、矿化体S、O、Pb、Re-Os同位素地球化学研究，获得了大量的数据，取得了较好的研究成果，这对区内今后的研究和深部找矿具有重要的意义。.本区岩石组合及岩浆活动的序列为：高钾钙碱性系列岩石组合为辉长闪长岩（142Ma）、石英二长闪长岩（138-142Ma）、花岗闪长（斑）岩（143-147Ma），橄榄安粗岩系列岩石组合为辉石二长闪长岩（137-142Ma）、二长岩（142-145Ma）、石英二长岩（139-141Ma），同一种岩性的岩浆存在多次侵位的特点。在3000米科学钻1750米以下发现的正长花岗岩为A型，时代为126Ma，标志着包括铜陵舒家店地区在内的中国东部构造环境此时达到伸展的高峰期。.研究表明，橄榄安粗岩系列侵入岩中的辉石堆积岩包体形成于45-60km深处；而高钾钙碱性系列侵入岩中大量的闪长质微粒包体，形成深度约为12-15km，是不同来源的岩浆混合的结果。锆石Lu-Hf同位素分析结果表明，橄榄安粗岩系列侵入岩主要来自富集地幔，混有少量的壳源成分，而高钾钙碱性系列侵入岩既有来自富集地幔的成分，又有古老地壳的成分。结合中国东部中生代岩浆活动的特点，认为铜陵舒家店地区深部岩石圈在147Ma前发生了拆沉作用，幔源基性岩浆上升到壳幔过渡带形成一个巨大的深位岩浆房，岩浆房自身的热和岩浆结晶潜热引起上部地壳低熔点组分部分熔融，形成浅位酸性岩浆房。橄榄安粗岩系列侵入岩主要来自深位岩浆房中分异的岩浆，而高钾钙碱性系列岩浆来自深位岩浆房分异的岩浆与浅位岩浆房酸性岩浆的混合。