91755213-Nature Communications:Alpine-style nappes thrust over ancient North China continental margin demonstrate large Archean horizontal plate motions
Abstract: Whether modern-style plate tectonics operated on early Earth is debated due to a paucity of defifinitive records of large-scale plate convergence, subduction, and collision in the Archean geological record. Archean Alpine-style sub-horizontal fold/thrust nappes in the Precambrian basement of China contain a Mariana-type subduction-initiation sequence of mid-ocean ridge basalt blocks in a 1600-kilometer-long mélange belt, overthrusting picritic-boninitic and island-arc tholeiite bearing nappes, in turn emplaced over a passive margin capping an ancient Archean continental fragment. Picrite-boninite and tholeiite units are 2698 ± 30 million years old marking the age of subduction initiation, with nappes emplaced over the passive margin at 2520 million years ago. Here, we show the life cycle of the subduction zone and ocean spanned circa 178 million years; conservative plate velocities of 2 centimeters per year yield a lateral transport distance of subducted oceanic crust of 3560 kilometers, pro viding direct positive evidence for horizontal plate tectonics in the Archean.