安徽贵池地区花岗闪长斑岩成岩与成矿

发布时间：2018-04-24 01:43

  本文选题：花岗闪长斑岩 + 锆石　； 参考：《合肥工业大学》2017年硕士论文

【摘要】：安徽贵池地区是长江中下游成矿带一个重要的成矿区,分布一系列铜、金、钼、多金属矿床。这些矿床与区内晚中生代花岗闪长斑岩体密切相关。虽然前人在成岩成矿方面取得了一定的成果,但这些花岗闪长斑岩成因及成矿仍存争议。本论文针对上述问题,选择贵池花岗闪长斑岩开展岩石学、矿物学、元素地球化学、锆石U-Pb年代学、锆石Hf同位素以及单矿物原位地球化学研究,结合前人的研究成果,获得如下认识。1.矿物地球化学研究表明贵池花岗闪长斑岩可能是壳幔混合的产物,而地壳成分占主要地位;岩浆的结晶温度在600℃~800℃。2.贵池花岗闪长斑岩(SiO_2=63.3%~64.8%)为高钾钙碱性Ⅰ型花岗岩,具有较低Cr(30×10~(-6)~50×10~(-6))含量,低Nb/U(3.40~7.23)和Nb/Ta比值(11.6~13.5),较高Mg#值,富集Rb、K,相对亏损Ba、Sr,轻稀土富集,重稀土亏损,有弱Eu负异常等这些特征说明幔源岩浆和壳源岩浆的混合可能是贵池花岗闪长斑岩形成的主要机制,而新元古代变质基底物质是其主要来源,岩浆演化过程中经历了明显的斜长石、钾长石和副矿物等结晶分异作用。其可能与古太平洋板块俯冲密切相关。3.高质量锆石U-Pb年龄结果表明贵池花岗闪长斑岩体为晚侏罗世,是长江中下游成矿带第一期岩浆活动的产物。4.锆石原位地球化学、Lu-Hf同位素特征(ε_(Hf)(t)=-12.7~-3.0,t_(DM2)=1.4~2.0Ga,以及磷灰石稀土元素特征进一步支持贵池花岗闪长斑岩为壳幔混合产物,而中元古—古元古代下地壳物质占主导地位。5.本区Cu、Mo、Au成矿作用与岩浆的高氧逸度密切相关。
[Abstract]:The Guichi area, Anhui Province, is an important metallogenic area in the middle and lower reaches of the Yangtze River, with a series of copper, gold, molybdenum and polymetallic deposits distributed. These deposits are closely related to the late Mesozoic granodiorite in the area. Although some achievements have been made in diagenesis and mineralization, the genesis and mineralization of these granodiorite porphyry are still controversial. In this paper, we select granodiorite porphyry in Guichi to study petrology, mineralogy, element geochemistry, zircon U-Pb chronology, zircon HF isotope and in situ geochemistry of single mineral. Gain the following knowledge. Mineral geochemistry shows that granodiorite porphyry may be the product of crust-mantle mixing, and the crustal composition is dominant, and the crystallization temperature of magma is at 600 鈩，

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