| 菅坤坤,高峰,杜彪,赵端昌,王星,何元方.喀喇昆仑天文点地区辉长岩锆石U-Pb年代学、地球化学特征及其构造意义[J].矿产勘查,2018,9(9):1693-1704 |
| 喀喇昆仑天文点地区辉长岩锆石U-Pb年代学、地球化学特征及其构造意义 |
| Zircon U-Pb geochronology, geochemistry and geotectonic applications of the gabbro from Tianwendian Region in the Karakorum |
| 投稿时间：2018-07-15 |
| DOI： |
| 中文关键词: 喀喇昆仑 新特提斯洋 辉长岩 伸展构造 |
| 英文关键词: Karakorum, Neo-Tethys, gabbro, extensional tectonic |
| 基金项目:新疆河尾滩-河西岗地区1∶5万矿产地质调查(编号DD20160004-5)资助。 |
|
| 摘要点击次数: 1292 |
| 全文下载次数: 729 |
| 中文摘要: |
| 新疆喀喇昆仑天文点地区广泛发育基性岩体,呈岩株状产出,岩性单一,主要由辉长岩和辉绿岩组成。采用LA-ICP-MS 锆石U-Pb 同位素定年法,获得辉长岩206Pb/238U加权平均年龄为(105±4) Ma,属早白垩世晚期。地球化学数据显示:岩石具有较低的SiO2(44.69%~48.54%),较高的Al2O3(13.6%~17.66%)和CaO(7.77%~11.04%)含量以及较高的Mg#。稀土总量中等(∑REE=78.57×10-6~119.3×10-6),轻重稀土元素分异较为明显[(La/Yb)N=4.28~5.72],弱的正铕异常(δEu=1.04~1.27)。岩石相对富集大离子亲石元素Rb、Ba、K,Pb明显正异常,轻度亏损高场强元素Nb、P、Zr等。微量元素地球化学特征显示岩浆起源于过渡型地幔的部分熔融,并且在上升侵位过程中发生明显的地壳混染。天文点一带辉长岩具有板内玄武岩的地球化学特征,综合认为其形成于陆内伸展体制,结合前人研究成果,认为新特提斯洋盆早白垩世晚期已经闭合,区内进入后碰撞伸展阶段。 |
| 英文摘要: |
| The intensively developed mafic intrusions with single lithology occuring as stocks in Tianwendian region of the Karakorum Mountains consist of gabbro and diabase.. The LA-ICP-MS zircon U-Pb dating of the Tianwendian gabbro yields an age of 105±4Ma,belonging to the late stage of the Early Cretaceous. Geochemical data indicate that the gabbros are low in SiO2(44.69%~48.54%), high in Al2O3(13.6%~17.66%), CaO(7.77%~11.04%) and Mg# value. They have medium REE(∑REE=78.57×10-6~119.3×10-6), the fractionation of light and heavy rare earth elements is obvious[(La/Yb)N=4.28~5.72], and slightly Eu anomalies(δEu=1.04~1.27). Those rocks with Pb positive anomaly are enriched in LILE and depleted in HFSE. Geochemical characteristics of trace elements indicate that those rocks originate from partial melting of the transitional mantle, with significant crustal contamination during ascending process. The gabbros in Tianwendian region have the similar geochemical characteristics to the intraplate basalts, therefore in comprehensive consideration, they are formed in an intra-continent extensional setting. Based on regional geology, we agree that the Neo-Tethys oceanic basin has closed in the late stage of the Early Cretaceous, and the Karakorum region stepped in the stage of post-collisional extension. |
|
查看全文
查看/发表评论 下载PDF阅读器 |
| 关闭 |
|
|
|