西藏日土白垩纪酸性侵入岩年代学及地球化学特征——对班公湖-怒江中特提斯洋盆闭合时限的制约

发布时间：2018-07-29 08:53

【摘要】：以西藏日土县北东地区的小型酸性侵入体为研究对象,结合岩石地球化学分析及锆石年龄测试,探讨岩石的成因类型及构造环境,确定班公湖-怒江中特提斯洋盆闭合的时限。研究区酸性岩体的岩性为黑云二长花岗岩,其主要组分的质量分数分别是:SiO_2为63.89%~77.49%,全碱(K_2O+Na_2O)为8.06%~8.95%,全铁(FeOT)为0.48%~4.37%,Al_2O_3为12.43%~16.17%;大离子亲石元素中Rb、Th、U、K明显富集,但Ba、Sr明显亏损;高场强元素中Nb、Ta、P、Ti明显亏损,而Zr、Hf相对富集;轻稀土元素相对富集、重稀土元素相对亏损,负Eu异常明显(δEu=0.09~0.67,平均为0.47),球粒原始标准化分布模式为向右缓倾的V型,属于A型花岗岩。其LA-ICP-MS锆石206Pb/238 U年龄加权平均值为(117.8±1.2)Ma,属于中生代早白垩世中期。从岩石碰撞后A1型花岗岩特征推测,班公湖-怒江中特提斯洋盆在日土地区的闭合时间应在早白垩世中期。
[Abstract]:Taking the small acidic intrusions in the northern and eastern part of Ritu County, Tibet as the research object, combined with geochemistry analysis and zircon age test, the genetic types and tectonic environment of the rocks are discussed, and the time limit for the closure of the Tethys ocean basin in the Bangong Lake-Nujiang River is determined. In the study area, the lithology of the acid rock body is black cloud monzogranite, the main components of which are: 1 SiO2 is 63.89g / g 77.49, the K _ 2O Na_2O is 8.06 ~ 8.95 and the total iron (FeOT) is 0.48 ~ 4.37 ~ 4.37% Al _ 2O _ 2O _ 3 is 12.4316.17; In the elements of high field strength, NbTa-TaPnTi is obviously depleted, while ZrHf is relatively enriched, light rare earth elements are relatively enriched, heavy rare earth elements are relatively depleted, negative EU anomalies are obvious (EU 未 ~ (0.09) 0.67 with an average of 0.47). The original standardized distribution model of spherical particles is a V-type with a gentle right inclination. It belongs to A-type granite. The weighted average of LA-ICP-MS zircon 206Pb/238 U age is (117.8 卤1. 2) Ma, which belongs to the middle Mesozoic early Cretaceous. According to the characteristics of A1 type granite after rock collision, it is inferred that the closing time of Tethys ocean basin in the middle of Bangong Lake and Nujiang River should be in the middle of early Cretaceous.
【作者单位】：成都理工大学地球科学学院;中国地质科学院矿产资源研究所;江西省地质调查研究院;
【基金】：中国地质调查局项目(1212011221085) 国土资源部公益性行业科研专项项目(201511017)
【分类号】：P588.12

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