Petrogenesis of Shilei quartz diorite in southern Jiangxi: Constraints from petrochemistry, trace elements of accessory minerals, zircon U-Pb dating, and Sr-Nd-Hf isotopes

Shilei quartz diorite is one of the most special diorites in Chongyi-Shangyou-Dayu area southern Jiangxi. Zircon U-Pb dating for one quartz diorite yields an emplacement age of 433.5 +/- 3.4 Ma. Four samples are with middle contents of silica (SiO(2): 56.92% similar to 64.70%), high contents of AL(2)O(3) (14.10% similar to 14.83%), Alk (6.41% similar to 7.40%), K(2)O (3.86% similar to 4.85%), MgO (3.47% similar to 5.95%) and FeO (5.23% similar to 8.14%) and low contents of P(2)O(5) (0.27% similar to 0.4%). They contain high contents of large ion lithophile elements such as K, Rb, Cs and light rare elements and low contents of high field strong elements such as Nb, Ta, Ti P. Apatites are enriched in rare elements, their light rare elements contents are much higher than heavy are elements contents. They have a low delta Eu (0.37 similar to 0.45). The Sr-Nd isotope compositions are characterized by the follows: Distinctively middle initial Sr isotopic ratios (I(sr) = 0.7073 similar to 0.7132); low initial Nd isotopic ratios (epsilon(Nd)(t) = -4.97 similar to -8.41), two-stage model age ranging from 1.58Ga to 1.86Ga; zircon Hf isotopic analysis yields main epsilon(Hf)(t) values of -8 to -2, with two-stage model age 1.77 +/- 0.09Ga. These characters indicate that Shilei quartz-diorite is the product of an intensive interaction between crust and mantle. The lithosphere of this area perhaps once thinned in Late-Caledonian.