| 安徽铜陵中生代侵入岩及其岩石包体中的硫化物-氧化物包裹体研究 |
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| 引用本文：秦新龙,曹毅.2010.Sulfide and oxide inclusions in xenoliths and host rocks of Tongling area, Anhui Province[J].Mineral Deposits,29(1):71~84 |
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| 基金项目:国家自然科学基金项目（40672045）、中国地质调查局项目（20089938）和教育 部科学技术研究重点项目（308006） |
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| 中文摘要:安徽铜陵地区中生代岩浆活动频繁，形成了一系列与铜、金多金属成 矿作用关系密切的中酸性侵入岩。在这些侵入岩中分布有大量的镁铁质团块、堆积晶和微粒 闪长质包体。在这些侵入岩及其岩石包体中观察到了一定数量的硫化物-氧化物包裹体。 文章对老庙基、小铜官山和小陶家岩体及其岩石包体中的硫化物-氧化物包裹体进行了详细的岩相学观察和 电子探针分析。观察和分析结果显示，镁铁质团块中硫化物包裹体内的矿物主要有磁黄铁矿、黄铜矿、单硫化物固溶体和镍黄铁矿，这些硫化物相（黄铜矿除外）中的Ni、Cu平均含量（wB，下同）分别为6.91%和0.44%；微粒闪长质包体和寄主岩中硫化物包裹体内的矿物主要为磁黄铁矿和黄铜矿，这些硫化物相（黄铜矿除外）中的Ni、Cu平均含量分别为0.44%、0.07%（微粒闪长质包体）和0.09%、0.42%（寄主岩）。镁铁质团块、微粒闪长质包体和 寄主岩中氧化物包裹体内的矿物分别为铬磁铁矿（Cr2O3平均含量为4.4%）、磁铁矿（Cr2O3平均含量为0.4%）和磁铁矿（Cr2O3平均含量为0.7%）；散布的氧化物颗 粒分别为铬磁铁矿（Cr2O3平均含量为6.8%）、磁铁矿+铬磁铁矿（Cr2O3平均含量为0.6%）和磁铁矿（Cr2O3平均含量为0.4%）。从单一包裹体中的矿物共生关系 来看，微粒闪长质包体和寄主岩中的矿物共生组合分别为磁黄铁矿+黄铜矿和磁黄铁矿+磁铁矿。而镁铁质团块中存在3种组合：① 单硫化物固溶体+磁黄铁矿；② 单硫化物固溶体+黄铜矿；③磁黄铁矿+镍黄铁矿+黄铜矿。矿物平衡温压计算结果表明，角闪石堆积晶、微粒闪长质包体和寄主岩的结晶温度分别为860 ～865℃、714～811℃ 和 614～733℃，对应的深度分别为26～27 km、7～16 km和3～6 km 。岩相学观察和电子探针分析结果结合已发表的地球化学、矿物学数据显示，铜陵地区镁铁质团块和角闪石堆积晶、微粒闪长质包体、寄主岩中的辉石和角闪石内的硫化物-氧化物包裹体分别是在上地幔到下地壳范围内，从碱性玄武质岩浆和轻度演化的底侵碱性玄武质岩浆 中熔离出来的不混溶硫化物-氧化物熔浆冷却结晶的产物；中-上地壳范围内，从辉长质-闪长质岩浆中熔离出来的不混溶的硫化物-氧化物熔浆冷却结晶的产物；上地壳范围内，从辉石（或石英）二长质-花岗闪长质岩浆中熔离出来的不混溶的硫化物-氧化物熔浆冷却结晶的产物。包裹体中的矿物组合及共生关系表明，从形成镁铁质团块到角闪石堆积晶，再到微粒闪长质包体和寄主岩的过程中，岩浆的结晶温度和深度依次降低，而受到地壳物质混染的程度逐渐增大。 |
| 中文关键词:地球化学 中生代 硫化物_氧化物包裹体 电子探针分析 岩石包体 中酸性侵入岩 长江中下游 |
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| Sulfide and oxide inclusions in xenoliths and host rocks of Tongling area, Anhui Province |
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| Abstract:This paper presents new petrographic observations and electron microprobe analyses of sulfide and oxide melt inclusions trapped within amphibole and clinopyroxene in xenoliths and host rocks (HRs) from the Late Jurassic-Early Cretaceous Laomiaojishan, Xiaotongguanshan and Xiaotaojia intrusions in Tongling area, Anhui Province. The plutons vary in composition from quartz monzonitic diorite to granodiorite, and contain mafic clots (MFCs), hornblende cumulates (HCs), and microgranular mafic enclaves (MMEs) with gabbroic to dioritic compositions. Compositions of sulfide inclusions correspond to pyrrhotite, chalcopyrite, single sulfide solution and pentlandite in MFCs, and pyrrhotite and chalcopyrite in MMEs and HRs. Ni and Cu content of the sulfide phases, except for chalcopyrite in single blebs, is averagely 6.91% and 0.44%, 0.44% and 0.07%, and 0.09% and 0.42% in MFCs, MMEs, and HRs, respectively. Compositions of oxide blebs correspond to Cr-magnetite(averagely 4.44% Cr2O3) in MFCs, and magnetite with an average Cr2O3 content of 0.44% in MMEs and 0.07% in HRs, while compositions of oxide grains are Cr-magnetite (averagely 6.58% Cr2O3) in MFCs, magnetite and Cr-magnetite (averagely 0.86% Cr2O3) in MMEs, and magnetite (averagely 0.34% Cr2O3) in HRs. Paragenetic associations of (1) mono sulfide solution + pyrrhotite, (2) mono sulfide solution + chalcopyrite, and (3) pyrrhotite and pentlandite + chalcopyrite exist within single blebs in MFCs, while paragenetic associations of pyrrhotite + chalcopyrite and pyrrhotite + magnetite occur within single blebs in MMEs and HRs, respectively. Crystallization temperatures of hornblendes in HCs and hornblendes and plagioclases in MMEs and HRs are 860～865℃, 714～811℃ and 614～733℃, respectively, based on Al and Ti in calcic amphibole and amphibole-plagioclase geothermometers. The pressures recorded by these phases indicate that they were formed at a depth of 26～27 km, 7～16 km, and 3～6 km, respectively, based on Al and Ti in calcic amphibole and Al-in-hornblende geobarometers. The present petrographic observations and microprobe analyses combined with the published geochemical and mineralogical data of the pyroxene cumulates, HCs, MMEs and HRs support an origin of sulfide and oxide melt inclusions in MFCs and HCs, MMEs, and HRs from crystallization products of sulfide and oxide melts immiscibly separated from alkaline basaltic and somewhat evolved underplated alkaline basaltic magmas from the upper mantle to the lower crust, the gabbroic to dioritic magmas in the middle to upper crust, and the pyroxene (or quartz) monzodioritic to granodioritic magmas in the upper crust, respectively. The variations in the oxide and sulfide assemblage and the sulfide and oxide paragenetic association within single blebs presented above correspond to the increase in the amount of the hybridized lower and middle to upper crustal material in the magmas and the decrease in crystallization temperature and depth of the magmas in the formation process of MFCs and HCs, MMEs, and HRs. |
| keywords:geochemistry, Mesozoic, sulfide and oxide inclusions, electron microprobe analysis, xenolith, intermediate-acidic intrusion, Lower Yangtze Ri ver Valley |
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