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The Geochemical and Zircon Trace Elements Characteristics of A‐type Granitoids in Boziguoer, Baicheng County, Xinjiang
Author(s) -
LIU Chunhua,
YIN Jingwu,
WU Cailai,
SHAO Xingkun,
YANG Haitao,
XU Haiming,
WANG Jun
Publication year - 2013
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.12161
Subject(s) - aegirine , zircon , geology , geochemistry , peralkaline rock , albite , monazite , alkali feldspar , feldspar , quartz , alkali metal , mineralogy , chemistry , organic chemistry , paleontology , volcano
The Boziguoer A‐type granitoids in Baicheng County, Xinjiang, belong to the northern margin of the Tarim platform as well as the neighboring EW‐oriented alkaline intrusive rocks. The rocks comprise an aegirine or arfvedsonite quartz alkali feldspar syenite, an aegirine or arfvedsonite alkali feldspar granite, and a biotite alkali feldspar syenite. The major rock‐forming minerals are albite, K‐feldspar, quartz, arfvedsonite, aegirine, and siderophyllite. The accessory minerals are mainly zircon, pyrochlore, thorite, fluorite, monazite, bastnaesite, xenotime, and astrophyllite. The chemical composition of the alkaline granitoids show that SiO 2 varies from 64.55% to 72.29% with a mean value of 67.32%, Na 2 O+K 2 O is high (9.85%–11.87%) with a mean of 11.14%, K 2 O is 2.39%–5.47% (mean = 4.73%), the K 2 O/Na 2 O ratios are 0.31–0.96, Al 2 O 3 ranges from 12.58% to 15.44%, and total FeO T is between 2.35% and 5.65%. CaO, MgO, MnO, and TiO 2 are low. The REE content is high and the total SREE is (263–1219) ppm (mean = 776 ppm), showing LREE enrichment and HREE depletion with strong negative Eu anomalies. In addition, the chondrite‐normalized REE patterns of the alkaline granitoids belong to the “seagull” pattern of the right‐type. The Zr content is (113–1246) ppm (mean = 594 ppm), Zr+Nb+Ce+Y is between (478–2203) ppm with a mean of 1362 ppm. Furthermore, the alkaline granitoids have high HFSE (Ga, Nb, Ta, Zr, and Hf) content and low LILE (Ba, K, and Sr) content. The Nb/Ta ratio varies from 7.23 to 32.59 (mean = 16.59) and the Zr/Hf ratio is 16.69–58.04 (mean = 36.80). The zircons are depleted in LREE and enriched in HREE. The chondrite‐normalized REE patterns of the zircons are of the “seagull” pattern of the left‐inclined type with strong negative Eu anomaly and without a Ce anomaly. The Boziguoer A‐type granitoids share similar features with A1‐type granites. The average temperature of the granitic magma was estimated at 832–839°C. The Boziguoer A‐type granitoids show crust–mantle mixing and may have formed in an anorogenic intraplate tectonic setting under high‐temperature, anhydrous, and low oxygen fugacity conditions.