Precambrian history of the Altun microcontinent: review and synthesis

Microcontinents in orogenic belts possess valuable records of orogenic process and provide insights for the reconstruction of supercontinents. The Central Altun terrane is an ancient block preserved in the Altun Orogen, located on the northwestern margin of the Qinghai-Tibet Plateau and the southeastern margin of the Tarim Craton. In this contribution, relevant published data and unpublished geological mapping reports are compiled, reviewed and synthesized, and an overview of the Precambrian history of the Central Altun terrane and its periphery is presented, including their formation, evolution, and tectonic processes. These data suggest that the Central Altun terrane, sandwiched by two Paleozoic ophiolite mélange belts, was a microcontinent comprising of Neoproterozoic clastic rocks, carbonate rocks and granitoids before it collided with Tarim craton in early Paleozoic. The geochronological data show the possible existence of Paleoproterozoic and Mesoproterozoic crystalline basement beneath the surface of the Altun Microcontinent. The Neoproterozoic geological records in the Altun orogen indicate that the northern and southern margins of the Altun Microcontinent were broken up simultaneously and are consistent with the supercontinent cycle, possibly triggered by a mantle plume that resulted in the break-up of the Rodinia supercontinent. Collectively, the geochronological data on both sides of the Altun Microcontinent suggest that it was not evolved independently until the break-up of the Rodinia supercontinent and may belong to Laurentia before that.