摘要:
治多地仁地区花岗岩侵位于松潘—甘孜地块南部, 该区花岗岩可划分为3个单元: 地仁石英闪长岩(T3δo)、日勤花岗闪长岩(T3γδ)、角考斑状二长花岗岩(T3πηγ),岩体呈小岩基、岩株产出.花岗岩属强过铝质,兼具I型和S型花岗岩的特点; Eu负异常明显, 轻重稀土分馏明显; Ta、Nb、Ce、Sm、Hf轻度富集, Y、Yb强烈亏损, Rb/Ba平均为0.38, Nb/Ta平均为16.44, 具下地壳源岩部分熔融花岗岩的特性; 单颗粒锆石U-Pb年龄介于210~225 Ma之间.由此可知, 该期花岗岩具有巴颜喀拉构造带碰撞造山后期花岗岩的特征.
Abstract:
Granites are distributed in the southern part of the Songpan–Ganzi block in Diren area of Zhiduo County, Qinghai Province. The granites in the study area can be divided into three units: Diren diorite (T3δo), Riqin granodiorite (T3γδ), and Jiaokao porphyry potash feldspar plagioclase granite (T3πηγ), The rock masses exhibit small batholiths and stocks. The granite belongs to aluminum type and has both I and S-type granite characteristics. Eu negative anomalies are obvious, with significant light and heavy rare earth fractionation. Ta, Nb, Ce, Sm, Hf are slightly enriched, Y and Yb are strongly depleted, Rb/Ba ratio is 0.38, and Nb/Ta ratio is 16.44. These data show that the granite has a crustal source rock, partly with the characteristics of molten granite. Single-grain zircon U-Pb ages range from 210 Ma to 225 Ma in the study area. It is thus held that the granite has the characteristics of collision late stage orogenic granite of the Bayankara tectonic belt.
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