藏南日喀则蛇绿岩中大洋斜长花岗岩锆石U-Pb年龄与Hf同位素特征及其岩石成因意义
需积分: 0 99 浏览量
2020-03-12
16:33:41
上传
评论
收藏 957KB PDF 举报
http://www.paper.edu.cn
- 1 -
中国科技论文在线
藏南日喀则蛇绿岩中大洋斜长花岗岩锆石
U-Pb 年龄与 Hf 同位素特征及其岩石成因意
义
#
王彭，戴紧根
**
5
基金项目：教育部博士点基金-新教师类(20130022120002)
作者简介：王彭（1994-），男，硕士研究生，主要研究方向：雅鲁藏布蛇绿岩成因
通信联系人：戴紧根（1983-），男，副教授，主要研究方向：雅鲁藏布蛇绿岩成因和高原隆升. E-mail:
（中国地质大学地球科学与资源学院，北京 100083）
摘要：大洋斜长花岗岩在现今大洋和造山带内的蛇绿岩中普遍存在。该类岩石中存在大量既
能用于测定年代又能用于示踪源区的锆石，因而斜长花岗岩是揭示蛇绿岩年代学和岩石成因
的重要单元。藏南日喀则蛇绿岩出露少量斜长花岗岩。本文对侵入橄榄岩的斜长花岗岩开展10
了锆石 U-Pb 定年和 Hf 同位素分析。两件样品锆石 U-Pb 年龄分别为 121.3±1.6Ma 和 122.3
±1.0 Ma，与目前所报道的蛇绿岩中镁铁质岩石的年龄一致。锆石εHf(t)值变化范围分别为
+11.0 至+16.3，和+12.6 至+16.4；TDM 模式年龄范围为 141-377 Ma 和 127-296 Ma。锆石
Hf 同位素组成与来自日喀则蛇绿岩中的镁铁质岩石相似，暗示其来自亏损源区。上述锆石
年代学和 Hf 同位素数据说明日喀则大洋斜长花岗岩与蛇绿岩形成同一时代，未遭受任何地15
壳浑染。结合全岩主微量元素与 Sr-Nd 同位素特征，进一步证实了日喀则斜长花岗岩是由俯
冲板片在含水条件下发生部分熔融形成。
关键词：日喀则蛇绿岩；大洋斜长花岗岩；锆石 U-Pb 年龄；锆石 Hf 同位素
中图分类号：P597+.3
20
Zircon U-Pb and Hf isotopic compositions of the oceanic
plagiogranites in the Xigaze ophiolites, south Tibet and
implications for the petrogenesis
Wang Peng, Dai Jingen
(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083) 25
Abstract: Plagiogranites occur in both the modern ocean and the ophiolites in the orogenic belt.
They are critical important for revealing the geochronology and petrogenesis for the ophiolites
because they are zircon-bearing. There are scattered plagiogranites in the Xigaze ophiolite, which
is one of the best-preserved ophiolite in the YarlungZangbo Suture Zone. Here we reported the
zircon U-Pb ages and Hf isotopic compositions for the plagiogranites which intruded into the 30
peridotites. Zircon U-Pb ages of two samples are 121.3±1.6 Ma and 122.3±1.0 Ma, respectively.
They are consistent with those of the ophiolites. The two samples poessess high positive εHf(t)
values of +11.0 to +16.3 and +12.6 to +16.4, respectively. Their Hf TDM model ages vary from
141 to 377 Ma and 127 to 296 Ma. The above Hf isotopic compositions of zircons resemble those
of the Xigaze ophiolites, indicating that they were derived from the depleted source. The above 35
resutlts indicate that the plagiogranite was generated synchronously with the ophiolite, and it was
not suffered from the continental crust contamination. Combined with its whole-rock major and
trace element and Sr-Nd isotopic composition, this study confirms that the plagiogranite was
generated by hydrous partial melting of subducted oceanic slab.
Key words: Xigaze ophiolite; Oceanic plagiogranite; Zircon U-Pb age; Zircon Hf isotope 40
评论0
最新资源