Abstract:

The Tieshiguan rock mass, located at the west-central segment of the northern margin of Qaidam basin, is composed of adakitic granite that was recently discovered in this area. The granite has high contents of SiO₂(71.36% to 73.70%), Al₂O₃(14.48% to 15.64%), and low content of MgO(0.44% to 0.71%); the trace elements display adakitic affinity, which are characterized by strong enrichment of Sr(＞350×10^-6), depletion of Yb(0.67×10^-6-1.58×10^-6) and Y(6.74×10^-6-18.02×10^-6), and high ratio of Sr/Y(21.32 to 72.49), enrichment of LREE and LILE, and depletion of HREE and HFSE. The Tieshiguan granite has ²⁰⁶Pb/²³⁸U weighted mean age of (422.0 ± 6.4)Ma, representing the magma formation age Studies have shown that the Tieshiguan granite is most likely formed by re-melting thickened continental crust in post-collisional orogenic stage.

Key words: northern Qaidam margin, zircon U-Pb dating, adakite, SP granite, collisional orogeny, Early Paleozoic