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Geochemistry of Alkali‐rich Igneous Rocks of Northern Xinjiang and Its Implications for Geodynamics
Author(s) -
Zhenhua ZHAO,
Zhenghua BAI,
Xiaolin XIONG,
Houjun MEI,
Yixian WANG
Publication year - 2000
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.1755-6724.2000.tb00469.x
Subject(s) - geology , geochemistry , igneous rock , orogeny , island arc , volcanic rock , continental crust , rift , earth science , geodynamics , tectonics , crust , subduction , volcano , paleontology
Five nearly E‐W‐trending alkali‐rich igneous rock belts are distributed from north to south in northern Xinjiang, and they are composed mainly of riebeckite, K‐feldspar granite and high‐K and medium‐K calc‐alkaline volcanic rocks and shoshonite. They were mainly emplaced or erupted between the Carboniferous and Permian. The compositions of Sr, Nd, Pb, and O isotopes imply that their principal resource materials are derived from the upper mantle or juvenile crust, indicating obvious continental growth in the Phanerozoic. The trace element association implies that their tectonic settings are within plate and volcanic arc for alkali‐rich granites, and post‐collisional are, late oceanic are and continental are for alkali‐rich volcanic rocks. An archipelago model was suggested for the tectonic evolution in northern Xinjiang. It can be named the central‐Asia‐type orogeny, which is different from the so called circum‐Pacific ocean‐continent‐type tectonics or the Alpine‐Himalayan continent‐continent‐collisional orogeny.