International Geologiical Congress - Oslo 2008

Home

Search Abstracts

Author Index

Symposia Programmes

Sponsors

Help

 

 

ASI-02 Geology and mineral resources of Northern and Central Eurasia

 

Thermo-Tectonic event group and stratigraphic system of Mesoproterozoic to Neoproterozoic in the central-northern Asia

 

Songnian Lu, Tianjin Institute of Geology and Mineral Resources (China)
Huaikun Li, Tianjin Institute of Geology and Mineral Resources (China)
 

 

The thermo-tectonic event groups and stratigraphic systems from Mesoproterozoic(1800 ∼ 1000Ma) to Neoproterozoic(1000Ma∼ 542Ma) in the Central-Northern Asia, including Siberia(SC), Tarim (TC), North China(NCC) and Yangtze(YC) Cratons, Central Asian and Central China Orogens, and adjacent Ural, will be focused.
Three event groups have been identified. The first one took place during 1.8 ∼ 1.6Ga.Geological records include mafic dyke swarms(1778±3Ma), anorthosite-mangerite-charnockite-rapakiwi granite suites(1693±7Ma), A-type granite(1625±16Ma) and high potassium volcanics(1625±6Ma). All of these formed after metamorphism, deformation, and magmatism of the Late Paleoproteorozoic Orogeny(2.0-1.85Ga) as products of intracratonic rifting events. The second is from 1.1Ga and 0.85Ga. The event group, involving arc volcanics(946±18Ma), calc-alkaline intrusions(955±5Ma) and high-grade metamorphism(962±12Ma), are controlled by assembly of continents. The third one related to a rifting environment is represented by layer mafic-ultramafic complex (825±36Ma), dyke swarms(827±12Ma), bimodal volcanics(819±10Ma) and A-type granite(819±35Ma). It is noteworthy that the first event group is mostly developed in the SC, NCC and Ural, but the second and third ones are well preserved in the TC and YC, and some Precambrian Massifs in the orogens.
In generally, the stratigraphic systems of Meso-Neoproterozoic can be subdivided into two gigantic sedimentary cycles based on sedimentry and tectonic environments. One is between 1.8Ga and 0.85Ga (for instance, the Changcheng, Jixian and Qingbaokou Groups in NCC, and Lower to Middle Riphean Group in Ural), and the other from 0.85Ga and 0.542Ga (at least including Nanhua and Sinain System in YC, and part of Upper Riphean and Vendian System in Ural).

The lower strata for each cycle are mainly composed of conglomerate, coarse terrestrial sandstone and volcanics in rifting basins. Following the beds, very thick carbonates deposited in a continental shelf environment are governed. The upper part of the cycles consists of arc volcanics and clastic beds related to an assembly environment of continents. However, the upper part of the second cycle should belong to the Palaozoic. It is noted that two glacial beds are well exposed at the Nanhua System in the TC and YC. According to new isotopic data, the time ranges of the two beds are roughly between 760∼ 680Ma and 650∼ 635ma, respectively.

Above thermo-tectonic event groups and stratigraphic systems are controlled by breakup of Nuna (or Columbia), assembly and disruption of Rodinia Supercontinent, respectively. On basis of the supercontinental cycle and geochronologic data, the stratigraphic subdivision and correlation of the Meso-Neoproterozoic in the area have been proposed in briefly.

 

CD-ROM Produced by X-CD Technologies