Discovery and Geological Significance of the Triassic High-Mg Diorites in
详细信息
- 责任者：Fu Changliang (College of Earth Sciences ; Jilin University ; Changchun 130061 ; China) ; Sun Deyou
- 刊名：Acta Petrologica Sinica
- 出版年：2010
- 卷期：26(4)
- 关键词：闪长岩 ; diorites ; 吉林 ; Jilin Province
- 页码：p.1089-1102
- 图表：illus., 3 tables, 76 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The high-Mg diorites newly discovered in Hunchu area, Jilin Province, is of importance for discussing the evolution history of the lithosphere in NE China. The zircon LA-ICPMS U-Pb ages for this type of rocks range from 241 to 240 Ma, and the contents of SiO2 and MgO are in the range of 51.93%～55.85% and 3.97%～10.38%, respectively. They are characterized by nearly flat REE patterns with LREE slightly enriched, and show enrichment of Rb and depletion of Ba, Nb, Ta, P and Ti. The values of 176Hf/177Hf and εHf(t) vary in the range of 0.282 672～0.283 085 and 1.78～15.95, respectively, suggesting they are of mantle origin. The minimum singlestage model age(tDM1=246 Ma) for this suite of rocks is similar to its emplacing age（t=240～241 Ma), suggesting there was a major crustal growth event occurred at～240 Ma in Yanbian area. The discrimination diagrams of Sr/Y(3.19～12.48)-Y(19.3×10-6～81.1×10-6) and(La/Yb)N(1.00～3.51)-YbN(4.15～14.62) show that the high-Mg diorites were likely formed in a mantle wedge setting similar to the magmatic processes of sanukitie. They are likely formed from mantle peridotites by reacting with Si-rich melts released from subducted oceanic slab. The comprehensive studies show that the Yanbian area was located in an active continental margin setting and affected by the subduction of Paleo-Asian Ocean plate towards North China plate before Early Triassic.