| dbo:abstract
|
- The Eastern Block of the North China Craton is one of the Earth's oldest pieces of continent. It is separated from the Western Block by the Trans-North China Orogen. It is situated in northeastern China and North Korea. The Block contains rock exposures older than 2.5 billion years (pre-Neoarchean and the Neoarchean Era). It serves as an ideal place to study how the crust was formed in the past and the related tectonic settings. Geologists are able to deduce the past environments and tectonic events by studying geological records like rocks and geological structures. The oldest components of the Eastern Block were first formed more than 4 billion years ago (the Hadean Eon). It later experienced numerous geological events between 3.8 and 1.85 billion years ago (the Eoarchean to Paleoproterozoic Era), including recurring volcanic eruptions and metamorphic events. Therefore, most of the rocks were reworked and highly metamorphosed with changes in minerals and texture. Due to the sparse exposure of pre-Neoarchean rocks, only the tectonic settings of the rocks generated from 2.7 to 1.85 billion years ago (during the Neoarchean and Paleoproterozoic Era) are thought to be understood. These settings include a Large Igneous Province event, mantle plume activity, continental collisions, rifting and subductions of plates. The Jiao-Liao-Ji Belt joined the two small blocks (the Longgang and Langrim blocks) together as the larger Eastern Block, whereas the Trans-North China Orogen shows the assembly of Eastern and Western Blocks, forming the North China Craton. The root of the craton was collapsed 130–120 million years ago (the Cretaceous Period), resulting in a thinner lithosphere. (en)
|
