Petrological and geochemical characteristics of Mesozoic adakite from Northern Huaiyang and discussion on its genesis.

作者：Pan GQ^*; Lu XC; Yu HB

来源：Acta Petrologica Sinica, 2001, 17(4): 541-550.

• adakite
• mesozoic
• Northern Huaiyang

Mesozoic magmatic rocks are widely emerged in north Huaiyang belt located in the backland of the Dabieshan orogenic belt. The geochemistry characteristics of igneous rocks formed from late Jurassic epoch to early Cretaceous epoch (150 similar to 130Ma) are similar to those of adakites with SiO2>56%, high Al content (Al(2)O(3)greater than or equal to 15% while SiO2>70%), high Sr content (Sr>400 mug/g), enrichment of Na (Na2O=3.34%similar to4. 75%, Na2O/K2O>1), low Y and Yb content (Y less than or equal to 18 mug/g, Sr/Y>20 similar to 40), La/Yb>20, Sr positive. and without obvious Eu anomaly. The adakites in this district present five rock types as (quartz) diorite, monzodiorite - granodiorite - monzogranite - granite, in which primary rock-forming minerals are aligoclase-andesine, microcline or orthoclase, Mg-biotite, quartz, and accessory minerals are assemblage of magne-titetitanite-zircon-apatite. Mica-riched and diorite-like xenoex are found in adakites, which proved that it belongs to the I-type granitoid in Origin. The igneous rocks at ages <130Ma belong to the A-type granitoid in origin instead of adakite. The origin of adakite may be ascribed to the partial melt of basaltic rocks underplated to lower crust, with the partial melt ratio at about 10->20%, and subsequently assimilation-fraction-crystallization (AFC) process occurred during the evolution of magma.

• 出版日期2001-10
• 单位南京大学