安徽宣城茶亭铜金矿床赋矿石英闪长玢岩锆石U-Pb年龄及岩石成因

发布时间：2018-04-15 03:14

本文选题：岩石成因 + U-Pb年龄　；参考：《高校地质学报》2017年04期

【摘要】：安徽宣城茶亭Cu-Au矿床是长江中下游成矿带内新发现的一个斑岩型矿床。文章对该矿床赋矿石英闪长玢岩进行了锆石LA-ICP-MS U-Pb同位素年龄及岩石主量与微量元素、Sr-Nd同位素和锆石Lu-Hf同位素分析,旨在探讨其岩浆起源和岩石成因。锆石U-Pb同位素年龄测定结果显示,赋矿石英闪长玢岩形成年龄为137.8±1.3 Ma(MSWD=0.72),为早白垩世岩浆活动的产物。岩石主量元素显示其具富碱富钠特征,为亚碱性准铝质高钾钙碱性系列岩石。岩石微量元素显示其富集大离子亲石元素K、Rb、Sr、Ba和轻稀土元素,弱富集Zr和Hf,亏损高场强元素Nb、Ta、Ti等,稀土元素配分型式表现为无明显Eu异常。岩石(~(87)Sr/~(86)Sr)_i值介于0.706403~0.707903之间,ε_(Nd)(t)值介于-7.4~-13.3之间(t=137.8 Ma)。锆石ε_(Hf)(t)值为-4.25~-11.75(t=137.8 Ma)。主量元素、微量元素、Sr-Nd同位素和锆石Hf同位素地球化学特征均指示,赋矿石英闪长玢岩可能是富集岩石圈地幔与扬子下地壳物质部分熔融形成的岩浆混合后侵位的产物。对比长江中下游成矿带断隆区和断凹区侵入岩发现,宣城茶亭矿床赋矿石英闪长玢岩与长江中下游成矿带断凹区(宁芜、庐枞矿集区等)侵入岩,无论是岩石主量与微量元素地球化学特征还是同位素地球化学特征都存在一定差异,而与断隆区(铜陵矿集区)赋矿岩浆岩表现出一致性,暗示宣城茶亭矿床赋矿石英闪长玢岩与长江中下游成矿带断隆区岩浆岩有着基本一致的成岩物质来源和岩石成因机制,是富集岩石圈地幔熔融岩浆及其引起的下地壳物质部分熔融岩浆发生岩浆混合作用并伴随着一定程度的分离结晶作用进而浅成侵位形成。
[Abstract]:The Cu-Au deposit in Xuancheng, Anhui Province is a porphyry deposit found in the middle and lower reaches of the Yangtze River.In this paper, zircon LA-ICP-MS U-Pb isotopic age, major rock mass and trace element Sr ND isotopes and zircon Lu-Hf isotopes are analyzed for the diorite porphyrite bearing ore in the deposit. The purpose of this paper is to discuss the magmatic origin and petrogenesis of the porphyrite.The U-Pb isotopic dating of zircon shows that the age of formation of diorite porphyrite is 137.8 卤1.3MaMS-WDX 0.72, which is the product of early Cretaceous magmatism.The main elements of the rocks show that they are rich in alkali and sodium, and belong to the subalkaline pseudo-aluminous high potassium calc-alkaline series rocks.The trace elements in the rocks show that they are rich in the large ion lithophile element K ~ (2 +) Rb ~ (2 +) Sr ~ (2 +) Ba and light rare earth elements, and are weakly enriched in Zr and HF, and depleted in the high field strength element Nb ~ (10) Ta-Ti, etc. The REE partitioning patterns show no obvious EU anomalies.The value of S / R / 86 / S / S / S / I is between 0.706403 and 0.707903, and the value of 蔚 _ S / N _ (D) is between -7.4 ~ 13.3 ~ 137.8 Ma ~ (-1).The value of zircon 蔚 -Hfnn is -4.25 ~ 11.75 ~ 137.8 Ma ~ (-1) ~ (-1) ~ (-1) ~ (-1) ~ (-1) ~ (-1) ~ (-1).The geochemical characteristics of major elements, trace element Sr ND isotopes and zircon HF isotopes indicate that the ore-bearing diorite porphyrite may be the product of magmatic emplacement resulting from the partial melting of the enriched lithospheric mantle and the lower Yangtze crust material.In contrast to the intrusive rocks in the middle and lower reaches of the Yangtze River in the fault-uplift and fault-sag areas, it is found that the Xuancheng Tea Ting deposit is filled with diorite porphyrite and the fault-sag areas of the middle and lower reaches of the Yangtze River (Ningwu, Luzong ore concentration, etc.) intrusive rocks.There are some differences in the geochemical characteristics of major and trace elements or isotopic geochemistry of rocks, but are consistent with the ore-bearing magmatic rocks in the faulted uplift area (Tongling ore concentration area).It is suggested that the ore-bearing diorite porphyrite is basically consistent with the magmatic rocks in the fault-uplift area of the middle and lower reaches of the Yangtze River.It is the magmatic mixing of enriched lithospheric mantle molten magma and the partial melting magma of the lower crust, which is accompanied by a certain degree of separation and crystallization and then the formation of superficial emplacement.
【作者单位】：合肥工业大学资源与环境工程学院;安徽省地质矿产勘查局322地质队;
【基金】：国家自然科学基金(41472066) 安徽省国土资源科技项目(2014K3)资助
【分类号】：P588.1;P618.2

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