Activation of the Central Kunlun Suture Zone, East Kunlun: Evidence from Carboniferous granites

In this publication, we identified Carboniferous intrusions for the first time in the Aksu River area, which has been relatively poorly explored in the western part of the East Kunlun.The Aksu acidic complex is located in the west section of the Central Kunlun fault zone.Zircon LA-ICP-MS dating results reveal that the granodiorite porphyry was crystallized at 361 ± 2.4 Ma, the monzogranite at 357.5 ± 2.8 Ma, and the granodiorite at 354 ± 4.3 Ma, indicating that these rocks were intruded during Late Devonian to Early Carboniferous(close to the west of Central Kunlun Suture Zone) and this stage of the magmatic event has not previously been publicly reported.Analysis of major elements classifies these rocks as belonging to the high potassium calc-alkaline to calc-alkaline and peraluminous series.Trace and rare earth elements indicate that all rocks are enriched in large ion lithophile elements(such as Th, U, Rb, K), light rare earth elements and depleted in high field strength elements(such as Nb, P, Ti).These granites have high initial ⁸⁷Sr/⁸⁶Sr(0.70612~0.71009), low whole-rock ε_Nd(t) values(-7.1~-5.1) and relative ancient T_DM2 model ages ranging from 1.51 Ga to 1.69 Ga, which is comparable to the composition of enriched mantle or crust in the East Kunlun Orogen.Mineralogical and geochemical analyses indicate that the rocks are I-type granites, formed by remelting of crustal material, suggesting that the Central Kunlun Suture Zone underwent extensional setting during the Carboniferous.Combined with the regional geology and available geochronological data, we propose that this extensional event should be the result of the initial expansion of a back-arc basin caused by subduction of the Paleo-Tethys Ocean, which also places the time of initial subduction of the Paleo-Tethys Ocean in the Carboniferous rather than the Permian.