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Geochemical Characteristics Petrogenesis of Jinfosi Pluton in Qilian Mountains(PDF)

《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]

Issue:
2006年第01期
Page:
5-12
Research Field:
Publishing date:

Info

Title:
Geochemical Characteristics Petrogenesis of Jinfosi Pluton in Qilian Mountains
Author(s):
HU Neng-gao1; SU Jian-ping 2; ZHANG Hai-feng2; FENG Bei-zhan2
1. School of Earth Sciences and Resources Management, Chang’ an University, Xi’an 710054, Shaanxi, China; 2. Gansu Institute of Geological Survey, Lanzhou 710050, Gansu, China
Keywords:
North Qilian orogen belt;  granite;  anatexis;  trace element;  Jinfosi pluton;  Gansu Province
PACS:
P588.12;P594.1
DOI:
-
Abstract:
The Jinfosi Pluton, a granitoid complex intruded in North Qilian Orogen Belt in late Silurian period, is mainly consisted of biotite monzogranite, biotite syenogranite and biotite quartz monzonite. The rocks of the plu- ton have 67.09%～ 74.97% w(SiO2), 1.18～ 1.83 w(K2O)/w(Na2O), and their w(TFeO), w(MgO),w(CaO) and w(Al2O3)decrease and w(K2O)increases with increasing w(SiO2). All rocks are peraluminous with ANKC of 1.06～ 1.24. The magmatic type belongs to calc-alkalic withσ= 1.25～ 2.48. The? REE varies from 21.36× 10 -6 to 254.90× 10 -6 and is negatively correlated to w(SiO2). Most of REE patterns show similarities in frac- tionating behaviour: LREE has more obviously fractionation than HREE;δ(Eu)vary from 0.64 to 0.19 and neg- ative Eu anomalies generally increase with increasing w(SiO2); Ni, Cr, Co, Sc, V and Sr decrease and Rb in- crease with increasing w(SiO2); Th is positively correlated to Th/U, but Ta is opposed to Nb/Ta. The varia- tions in abundances of major, rare earth and trace elements in the pluton resulted mainly from the anatectic process and did not from the crystallization differentation. These data indicate that the source rocks of the pluton are mainly rich-felsic and poor-argillaceous. The mineral assemblage of the source rocks is possible of hornblende + biotite+ plagioclase+ K-feldspar+ quartz, which belongs to the Beidahe Group.

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Last Update: 2006-03-20