Continental Crust Material in Subduction Complex in Southwestern Tianshan-Geochemical Implications from Metabasic Rocks
详细信息
- 责任者：Liu Xin (State Key Laboratory of Lithosphere Evolution ; Institute of Geology and Geophysics ; Chinese Academy of Sciences ; Beijing 100029 ; China) ; Su Wen
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(5)
- 关键词：杂岩 ; complexes ; 变质作用 ; metamorphism ; 天山 ; Tianshan Mountains
- 页码：p.1675-1684
- 图表：illus., 2 tables, 42 refs.
- 分类号：0802
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
A new eclogite block,which is intercalated with garnet-bearing mica schist as lens and retrograded to blueschist in the interface,was found in the Atantayi valley in the southwestern Tianshan HP / UHP metamorphic belt. The eclogite and blueschist have similar geochemical characteristics: the SiO2 and TiO2 of the eclogite is 51. 59% ～ 52. 66% and 0. 70% ～ 0. 80% ,respectively; for the blueschist the value is 51. 57% ～ 54. 06% and 0. 86% ～ 0. 89% . Both of the eclogite and blueschist have a LREE-enriched, HREE flat and moderate negative Eu anomaly REE pattern,and both kinds of rocks depleted in Ba,Sr,Nb,Ta,Ti,the La / Nb is 3. 0 ～ 4. 8 and 2. 1 ～ 3. 7,respectively,resemble the geochemical characteristics of the arc magmatic rocks in active continental margin. The Zr/Hf and Nb/Ta of the eclogite is 36. 5 ～ 37. 1 and 10. 2 ～ 12. 9,and for the buleschist is 35. 9 ～ 36. 4 and 11. 2 ～ 12. 6. Both of the ratios are similar to that of the continental crust. For the eclogite,( 87Sr / 86Sr)i = 0. 7091 ～ 0. 7095,εNd (t) = -7. 52 ～ -6. 31, and the value of the blueschist is 0. 7098 ～ 0. 7107 and - 7. 70 ～ - 7. 13. The geochemical characteristics and Sr-Nd isotope system of the eclogite and blueschist suggest that their protolith have continental crust affinity. It suggests that there is continental material in the southwestern Tianshan subduction complex.
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