Identification of lateral inhomogeneity of arc basement by reconstructing the Late Devonian arc belt in the southwestern Central Asian Orogenic Belt

Abstract

A reconstruction of the Late Devonian arc belt in the West Junggar and adjacent Kazakhstan regions is crucial for understanding the architecture of the southwestern part of the Central Asian Orogenic Belt. Here, we report zircon U–Pb age, elemental, and Sr–Nd isotopic data for the firstly recognized Late Devonian pluton in the central West Junggar terrane (NW China) to constrain the component of the inner arc belt (IAB) of the Kazakhstan Orocline. Dioritic rocks from the pluton, dated at ∼368 Ma, are calc-alkaline and display negative Nb–Ta–Ti anomalies and positive εNd(t) values ranging from +6.6 to +7.0, implying a juvenile arc setting. Such a Late Devonian arc may thus represent the eastern part of the northern limb of the IAB, but it was built on early Paleozoic accreted terranes, which is distinct from a Precambrian continental basement for the coeval arcs in the central and southern parts of IAB. This difference could be attributed to the lateral inhomogeneity of arc basement, similar to the Aleutian arcs.