| 宁芜盆地凹山和东山铁矿床中阳起石的激光39Ar-40Ar年代学研究 |
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| 引用本文：蒋少涌,薛怀民.2010.Early Cretaceous mineralizations in Ningwu basin: Insight from actinolite 39Ar-40Ar laser dating results [J].Mineral Deposits,29(2):283~289 |
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| 基金项目:国家自然科学基金（40503006）和中国地质调查局项目（1212010711814） |
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| 中文摘要:文章通过对凹山和东山铁矿床中特征的组合矿物之一伟晶状阳起石进 行激光39Ar-40Ar法定年，精确测定了玢岩铁矿的成矿时代。其中东山铁矿中新鲜 阳起石（黑绿色）的39Ar-40Ar等时线年龄在126～129 Ma之间，与赋矿围岩大王山组火山岩 中角闪石的等时线年龄（127 Ma）一致，证明成矿与成岩密切相关，成矿与成岩是同时期的产物。而凹山铁矿中蚀变 阳起石（灰绿色）的39Ar-40Ar等时线年龄为（114 ±16）Ma。2种阳起石分别形成于成矿作 用的不同阶段，黑绿色新鲜阳起石与磷灰石、磁铁矿同期形成，形成于岩浆向热液演化的高温阶段，在成岩和成矿之后的冷却过程中，矿体和潜火山岩体具有相同的闪石封闭温度（500℃ ±）；而灰绿色蚀变阳起石形成于中期阳起石（透辉石）-钠长石-磷灰石-磁铁矿化矿体围 岩蚀变阶段。 |
| 中文关键词:地球化学 阳起石 激光39Ar-40Ar定年 玢岩铁矿 宁芜盆地 |
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| Early Cretaceous mineralizations in Ningwu basin: Insight from actinolite 39Ar-40Ar laser dating results |
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| Abstract:Actinolite 39Ar-40Ar laser fusion technique was employed to determine the metallogenic epochs of the Ningwu porphyrite iron deposits. The 39Ar-40Ar isochron ages of the fresh actinolite (dark green) from the Dongshan iron deposit are from 126 to 129 Ma, which agree with the 39Ar-40Ar isochron age (127 Ma) of hornblende from the host volcanic rock of Dawangshan Group within the analytical errors, indicating that iron mineralization was associated with the Dawangshan Group volcanic rocks. The 39Ar-40Ar spectrum ages of altered actinolite (gray green) from the Washan iron deposit is (114 ±16) Ma. The two kinds of actinolites were formed at different metallization stages. The dark green actinolite was formed sy nchronously with apatite and magnet when the temperatures of the subvolcanic roc k and the ore body fell to the hornblende closure temperature (ca. 500℃). The g ray green altered actinolite was formed at the middle stage of the actinolite (d iopside) albite apatite magnetic wall rock alteration. |
| keywords:geochemistry, actinolite, 39Ar-40Ar dating, prophyrite, iron deposit, Ningwu basin |
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