Geochemistry of the Paleoproterozoic Pandaoling pluton in Xiuyan area of eastern part of Liaoning Province and its implications for tectonic setting

This paper is the result of geological survey engineering.

Objective The Paleo-Proterozoic Pandaoling pluton is a granitic body in the Liaoji active belt, Eastern Block of the North China Craton, which is mainly composed by biotite monzogranite. It has been seldom researched so far, which restricts the recognition of evolution of tectonic setting in North China.

Methods Based on the field geological characteristics of the Pandaoling pluton, it has been studied in terms of petrography and geochemistry in this paper.

Results The rocks contain high silicon (74.04%-75.84%), high potassium (3.81% in average) and are rich in alkali (Na₂O+K₂O=7.29%-7.87%), and the average value of K₂O/Na₂O and A/CNK are 1.09 and 1.187-1.394, respectively. The rocks belong to high-K, calc-alkaline series peraluminous I-type granite. The granites have low ΣREE contents (with average of 89.78×10^-6) and obvious negative Eu anomalies (0.19-0.93). They has variable (La/Yb)_N ratios of 2.95 to 50.38, and display enriched LREE patterns, with relatively enrichment of LILEs (Rb, K, U) and HFSEs (Hf), and low contents of Ba, Zr, Nb, Ta, P and Ti. Zircon saturation temperatures (745-774℃) of granite melt are significantly lower than the A-type granites (868℃-928℃). These characteristics suggest that the Pandaoling monzogranite is characteristic of high fractionated I-type granite.

Conclusions The petrological and geochemical features of the Pandaoling pluton indicate that they were originated from partial melting of the deep crust due to mantle magma intraplating. Based on tectonic history and the diagram of structure environment, the Pandaoling pluton was possibly formed in the continental borderland collision tectonic setting of Liaoji Paleoproterozoic active blet.