South China Craton

South China Block is formed by the assembly of both the Yangtze and Cathaysia blocks along the northeasterly trending Jiang-Shao Fault. However, the southwestern extension of this suture is poorly understood due to poor exposure. Yangtze Block contains several Archean—Paleoproterozoic crystalline basements (e.g. Kongling Complex). The igneous rocks are unconformably overlain by weakly metamorphosed Neoproterozoic sequences (e.g., Banxi Group) and unmetamorphosed Sinian units. In contrast, the Cathaysia block does not contain any Archean basement. Instead, it is composed of mainly Neoproterozoic basement rocks. Rare occurrence of Paleoproterozoic rocks and Mesoproterozoic rocks are reported in southwest Zhejiang and Hainan Island respectively. Paleozoic magmatism is not common in the South China Block. However, a late Permian Emeishan large igneous province is reported in the western margin of the Yangtze Block. Mesozoic magmatism is very extensive, especially in the Cathaysia block. == Components ==

This section focuses on how the components of the South China Block were formed. The South China Block is traditionally divided into the Yangtze Block in the northwest and the Cathaysia Block in the southeast. -->The study of the formation of the Yangtze Block is challenging due to rare Archean outcrops. It is believed that it was formed at around 3.8 – 3.2 Ga. Yangtze Block later became part of the Columbia, but its position has only been constrained poorly. The U-Pb crystallization age distribution of 7000 detrital zircons is characterized by several peaks over the history of Earth spans. Those peaks coincide with the age of supercontinent assembly. However, the position of the block is poorly known. It possibly connected with North China, western Australia and/or northwestern Laurentia. Cathaysia Block is divided into three stages. The continental blocks first converge by subduction. Then, They collide to form the supercontinent. Finally, they drift apart from each other, leading to the supercontinent breakup. The interplay between magma generation and preservation potential of the detrital zircon determine the age distribution of the detrital zircon in three stages. Although the volume of magma generated is low during collision, the high preservation potential results in a peak of the number of detrital zircon. Therefore, the age peak is coincident with the assembly of the supercontinent. Blue: Magma volume. Red: Preservation potential. Brown area: Age distribution of the detrital zircon. Modified from Hawkesworth et al. (2009). This idea is challenged by the fact that the zircons are oval in shape. They were possibly transported a long distance from another block that was once close to the Cathaysia Block. It is suggested that the Late Archean oval-shaped detrital zircons were brought from those blocks. Tolo Terrane The study of the Tolo Terrane is at the initial stage. Most of the evidence comes from Hong Kong. The Tolo Terrane possibly represents a fragment of the Qiangtang Terrane. When the South China Block collided with the India Craton in the Cambrian, the Qiangtang Terrane was sandwiched between those two blocks. During the collision, a fragment (i.e. Tolo Terrane) was calved off from the Qiangtang Terrane. == Formation ==

This section focuses on how the South China Block was formed. Traditionally, the South China Block was formed by the collision between the Yangtze Block and the Cathaysia Block in the Neoproterozoic. • The process of amalgamation is uncertain. • The genesis of the Neoproterozoic (830—740 Ma) post-collision magmatism is unclear. • The position in the Rodinia supercontinent is controversial. Timing of amalgamation There are two schools of thought. • They were separated by an early or late Paleozoic ocean. (e.g. intra-oceanic arc versus continental arc, backarc versus forearc). Despite so, only divergent double subduction system can provide plausible explanation on two key observations in the Jiangnan Orogen. When they were incorporated into the margins, sedimentary rocks might be melted to form granitic magma. Therefore, the formation age corresponds to the final time of amalgamation. • A 830 Ma prominent angular unconformity is reported. Ideally, the syn-collision rock strata deformed but the post-collision rock strata did not. Therefore, the age of the angular unconfomity can reveal the termination age of collision.|alt=|400x400px --> When the Tolo Terrane was split from the Qiangtang Terrane, it was removed from the collision system by a strike-slip fault. If this is correct, the Tolo Terrane should be considered as part of the Cathaysia Block, rather than a distinct unit. == Evolution ==

Following the traditional definition, the South China Block was formed by the collision between the Yangtze Block and the Cathaysia Block in the Neoproterozoic. The granitic rock includes biotite monzonitic granite and muscovite-, garnet-, and tourmaline-bearing granites. • The Pressure-Temperature curve of the metamorphic rock shows a clockwise curve. The rocks in the lower portion of the lithosphere might be converted into eclogite (i.e. a very dense rock) due to the high pressure burden. Subsequently, it collided with the northwest India Craton in the Gondwana margin by the Cambrian. Closure of the ocean led to collision between those two blocks and subsequent deformation, magmatism and metamorphism. Petrological and geochemical results provide indisputable evidence for supporting a mantle plume origin. For example, the picrites is proved to represent a high temperature primary magma. Indosinian and Yanshanian Movement