Age and generation of Fogang granite batholith and Wushi diorite-hornblende gabbro body

• Published in: Science China. Earth sciences Vol. 50; no. 2; pp. 209 - 220
• Main Authors: Xu, XiSheng, Lu, WeiMin, He, ZhenYu
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01.02.2007; State Key Laboratory of Crust-Mantle Evolution and Mineralization,Department of Earth Sciences, Nanjing University, Nanjing, 210093, China
• Subjects: Dehydration; Geology; Magma; Mesozoic; Rocks; isotopic dating; source component; higher initial 87Sr/86Sr diorite; Nanling; granite
• ISSN: 1006-9313; 1674-7313; 1862-2801; 1869-1897
• DOI: 10.1007/s11430-007-2068-3

Fogang granitic batholith, the largest Late Mesozoic batholith in the Nanling region, has an exposure area of ca. 6000 km^sup 2^. Wushi diorite-homblende gabbro body is situated at the northeast part of the batholith. Both the granitic batholith main body and the diorite-homblende gabbro body belong to high-K calc alkaline series. Compared with the granitic main body, the Wushi body has lower Si (49%-55%), higher Fe, Mg, Ca, lower REE, less depletion of Eu, Ba, P, Ti, and obvious depletion of Zr, Hf. Zircon LA-ICP-MS dating and the mineral-whole rock isochron dating reveal that Fogang granitic main body and Wushi body were generated simultaneously at ca. 160 Ma. The Fogang granitic main body has high (^sup 87^Sr/^sup 86^Sr)^sub i^ ratios (0.70871-0.71570) and low ^sub Nd^(t) values (-5.11--8.93), suggesting the origins of the granitic rocks from crustal materials. Their Nd two-stage model ages range from 1.37-1.68 Ga. The Sr and Nd isotopic compositions and the Nd model ages of the granitic rocks may suggest that the giant Fogang granitic main body was generated from a heterogeneous source, with participation of mantle component. Wushi diorite-homblende gabbro is an unusual intermediate-basic magmatic rock series, with high (^sup 87^Sr/^sup 86^Sr)^sub i^ ratios (0.71256-0.71318) and low ^sub Nd^(t) values (-7.32--7.92), which was possibly formed through mixing between the mantle-derived juvenile basaltic magma and the magma produced by the dehydration melting of lower crustal basaltic rocks.[PUBLICATION ABSTRACT]