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Permian High Ba‐Sr Granitoids: Geochemistry, Age and Tectonic Implications of Erlangshan Pluton, Urad Zhongqi, Inner Mongolia
Author(s) -
LUO Hongling,
WU Tairan,
ZHAO Lei,
HE Yuankai,
JIN Xu
Publication year - 2009
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/j.1755-6724.2009.00054.x
Subject(s) - pluton , lile , geology , geochemistry , mafic , zircon , fractional crystallization (geology) , mantle (geology) , lithophile , crust , partial melting , petrology , tectonics , paleontology
Erlangshan Pluton from Urad Zhongqi, central Inner Mongolia, is located in the middle segment of the northern margin of the North China Plate. The rocks consist mainly of diorites with gneissic structure. Petrochemical characteristics reveal that the diorites belong to metaluminous, high‐potassium calc‐alkaline series, with chemical signatures of I‐type granites. They are characterized by low SiO 2 contents (56.63%–58.53%) and A/CNK (0.90–0.96), high Al 2 O 3 contents (17.30%–17.96%) and Na 2 O/K 2 O ratios (1.20–1.70), enrichment in large ion lithophile elements (LILE, e.g., Ba=556–915 ppm, Sr=463–595 ppm), and relative depletion in high field strength elements (HFSE, e.g., Nb, Ta, Ti) in primitive mantle‐normalized spidergram, and right‐declined rare earth element patterns with slightly negative Eu anomalies (δEu=0.72–0.90). They have Sr/Y ratios (20–25) evidently less than Kebu Pluton (49–75) to its east. Sensitive high resolution ion micro‐probe U‐Pb zircon dating of the diorites has yielded an intrusive age of 270±8 Ma. This leads us to conclude that Erlangshan diorites were formed by mixing between the middle or lower crustal‐derived magma and minor mantle‐derived mafic magma, followed by fractional crystallization, which was trigged by crustal extension and fault activity in post‐collisional setting.