The Missing Magmatic Arc in a Long‐Lived Ocean From the Western Kunlun‐ Pamir Paleo‐Tethys Realm
Gong‐Jian Tang, Peter A. Cawood, Derek A. Wyman, Wei Dan, Qiang Wang, Ya‐Nan Yang
Abstract
Abstract The evolution of the western Kunlun‐Pamir region involved the opening and closing of several branches of the Paleo‐Tethys Ocean, although the specific timing of these events is poorly constrained. Here, we present a synthesis of sedimentary, magmatic, and metamorphic records associated from the Mazar‐Kangxiwa suture zone in the western Kunlun‐Pamir that is generally regarded as the main Paleo‐Tethys Ocean suture. These data show that the Paleo‐Tethyan oceanic basin opened at ca. 340 Ma and closed by ca. 250 Ma, and there is no record of a magmatic arc between ca. 300–250 Ma. The absence of a magmatic arc was a result of oceanic crust underthrusting, rather than oceanic subduction, which is consistent with a narrow back‐arc basin. Our study provides an important example of how an oceanic basin opened and closed without oceanic subduction, and highlights a potential mechanism to account for the absence of a magmatic arc.