Citation: | WANG Jun, LI Xiaoqiang, LIANG Minghong, WANG Yuxi, ZHANG Bingbing, PAN Baotian. Age and geochemistry of Aksay ophiolite in East Altun Mountains[J]. Geological Bulletin of China, 2018, 37(4): 559-569. |
North Altun ophiolite belt is an ophiolite melange zone located on the northern margin of the Altun Mountains. Rock associations of ultrabasic rock blocks, basic dyke swarms, gabbro rock blocks and basic lava composite the representative ophiolite suite located in Aksay of the East Altun Mountains. Geochemical studies of the Aksay ophiolite show that the ultrabasic serpentinite is high in MgO and poor in Al2O3, P2O5, CaO, K2O, the chondrite-normalized REE patterns are relatively flat, and the ratio of sample to chondrite is close to 1. Basic lava rock is recognized by content of TiO2, Al2O3, CaO, with the chondrite-normalized REE patterns being relatively right-inclined. Basic dyke swarms are recognized by content of TiO2, Al2O3, with the features of Na2O higher than K2O, ∑ REE, and ∑ LREE/∑ HREE(2.22~4.45). Geochemical studies indicate that the Aksay ophiolite was formed in a Mid-Ocean Ridges (MOR) environment and was reformed by subsequent Suprs-Subduction Zone (SSZ). Geochronologic studies of zircon U-Pb show that the Aksay ophiolite was generated at 514.6±8.8Ma of Cambrian period.
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Tectonic location of the study area(a) and sampling sites in Aksay ophiolite zone(b)
Ultrabasic rock in Aksay ophiolite zone
Chondrite-normalized REE patterns of ultrabasic rock from Aksay ophiolite
Diagrams of Aksay basic lava
Diagrams of Aksay ophiolite basic dyke swarms
CL images of zircons from the Aksay ophiolite (a) and 206Pb/238U ages (b)