Geochemical Characteristics and Geological Significance of Adakitic Granitoids in Xiahe County of Gansu Province

详细信息   

• 责任者：Yin Xianming （Gansu Provincial Bureau of Geology and Mineral Exploration and Development ; Lanzhou 730000 ; China）
• 刊名：Gansu Geology
• 出版年：2008
• 卷期：17(3)
• 关键词：埃达克岩 ; adakite ; 甘肃 ; Gansu
• 页码：p.6-12
• 图表：5 illus., 1 table, 40 refs.
• 分类号：0801
• issnNo：ISSN1004-4116
• isbnNo：CN 62-1191/P

摘要

The late Indosinian granitoids in Xiahe area of Gansu Province belong to west Qinling orogenic belt. A study of their petrochemical and geochemical characteristics shows that they have the typical characteristics of “adakite”. These rocks have the following characteristics: most of SiO₂ (70%～58%); high Al₂O₃(16. 7%～14.6%) and Sr (most of them >400×10^-6); and low in Sr/Y(16×10^-6～7×10^-6) and Y ratio (1. 7×10^-6～0. 56×10^-6). There exist very prominent negative Nb and Ta anomaly in the trace element spidergram. REE distribution patterns show strong REE segregation and belong to the type of enriched LREE, but depletion in HREE, and weak negative Eu (δEu=0. 9～0. 4) auanomaly can be observed, and most samples fall into the extent of adakite on (La/Yb)N-YbN and Sr/Y-Y diagrams. Therefore, the discoveries of the adakitic rocks have great significance for the study on Late Paleozoic tectonic evolution of Qinling orogenic belt.