【摘要】 塔里木盆地东南缘的阿克塔什塔格地区,变质基底杂岩中发育火成碳酸岩侵入体,呈似层状侵入于米兰岩群和新太古代TTG花岗片麻岩中。碳酸岩主要由方解石(45%～90%)、透辉石(15%)和含量不等的石英、长石等矿物组成,可见少量金云母、方柱石,矿物组成较为简单。常量元素中Fe、Mg、Mn、Ti、P等元素低于世界已知幔源碳酸岩10个数量级之上,而Si、Al含量较高;微量元素富集大离子亲石元素Rb、Th、K和轻稀土元素,亏损高场强元素Nb、Ta、Sr、Ti,并且稀土总量仅为(25.74～63.01)×10-6,锆石Th/U比为0.04～0.36。上述特征明显有别于幔源成因的碳酸岩,可能指示米兰岩群大理岩在古元古代的深熔作用,即由米兰岩群中的大理岩在古元古代深熔作用条件下形成。挑选其中的锆石利用U-Pb SHRIMP法测年,获得年龄为(1 931±18)Ma。该碳酸岩体的发现不仅丰富了壳源碳酸岩的成因类型,也暗示塔里木克拉通的新太古代基底变质岩在古元古代末期发生过深熔作用和混合岩化,是塔里木克拉通对全球哥伦比亚超大陆的汇聚事件的响应。更多还原

【Abstract】 The igneous carbonatite identified within the basement metamorphic complex of Aqtashtage Area in Southeastern Tarim Basin,are discovered intruding into Neoarchean TTG gneiss and Milan Group.The carbonatite intrusion has relatively simple mineral assembly,consisting of calcite(45%90%),diopside(15%),some quartz and feldspar,and minor phlogopite and scapolite.The major elements show at least 10 order of magnitude lower Fe,Mg,Mn,Ti,and P contents than the known mantle-derived carbonatite in the world and higher Si,Al contents.Concerning the trace elements,the carbonatite rocks are enriched in LILEs such as Rb,Th,K and LREE,depleted in HFSE-Nb,Ta,Sr,and Ti,with low ΣREE content.Combined with zircon Th/U ratios(0.040.36),all of geochemical features mentioned above indicate that the carbonatite rocks are of crustal origin produced by anatexis of Milan group marble in the Paleoproterozoic.The age of the igneous zircon in this carbonatite pluton by U-Pb SHRIMP dating is(1931±18) Ma.The discovery of this carbonatite intrusion not only enriched the genesis of carbonatite of crustal origin,but also suggested that the Neo-Archean basement complex of Tarim Craton had undergone anatexis and migmatitization,as a response of Tarim Craton to worldwide Columbia supercontinent aggregation.更多还原