Preliminary Proterozoic apparent polar wander paths for the South China Block and their tectonic implications

1998 ◽  
Vol 35 (3) ◽  
pp. 302-320 ◽  
Author(s):  
Huimin Zhang

Results of a regional paleomagnetic study of Precambrian rocks in central-east China are summarized and interpreted. The study is a partial outcome of a geoscience transect incorporating three terranes, namely the Yangzi, Jiangnan, and Huaxia blocks. Paleomagnetic poles derived from a range of metamorphic, igneous, and sedimentary rocks define a northeast to southwest swath crossing the present Pacific Ocean and interpreted to embrace Early to Late Proterozoic times. All three terranes define segments of the same swath and correlate with a similar apparent polar wander path previously defined from the North China Block. The results imply that the constituent blocks of eastern China formed a united block during Early to Middle Proterozoic times. Later relatively large fragmentation is confirmed by Late Proterozoic apparent polar wander path records of the North China and South China Blocks.

1991 ◽  
Vol 104 (1) ◽  
pp. 29-40 ◽  
Author(s):  
Zhong Zheng ◽  
Masaru Kono ◽  
Hideo Tsunakawa ◽  
Gaku Kimura ◽  
Qingyun Wei ◽  
...  

Refined Apparent Polar Wander (APW) paths for the North and South China Blocks (ncb and scb) are presented and the collision between the NCB and SCB discussed. We suggest that the amalgamation of the NCB and SCB was completed in the late Triassic-early Jurassic, during the Indosinian Orogeny. This proposed timing is based on an analysis of palaeomagnetic signatures relating to continental collisions, such as the convergence of palaeolatitude, deflections of declination, hairpin-like loops in and superposition of APW paths. Like the Cenozoic India—Eurasia collision, the Mesozoic NCB- SCB collision reactivated ancient faults in eastern China, converting some of them into transcurrent faults, of which the Tan-Lu fault is the most famous.


1998 ◽  
Vol 41 (S2) ◽  
pp. 51-65 ◽  
Author(s):  
Yang Zhenyu ◽  
Ma Xinghua ◽  
Huang Baochun ◽  
Sun Zhiming ◽  
Zhou Yaoxiu

2020 ◽  
pp. 753-774
Author(s):  
Kun-Feng Qiu ◽  
Richard J. Goldfarb ◽  
Jun Deng ◽  
Hao-Cheng Yu ◽  
Zong-Yang Gou ◽  
...  

Abstract The Jiaodong gold province, within the eastern margin of the North China block and the translated northeastern edge of the South China block, has a stated premining gold resource exceeding 4,500 metric tons (t). It is thus one of the world’s largest gold provinces, with a present cumulative annual production estimated at 60 t Au. More than 90% of the Jiaodong gold resource is hosted by batholiths and related bodies of the Linglong (ca. 160–145 Ma) and, to a lesser degree, Guojialing (ca. 130–122 Ma) suites. The intrusions were emplaced into high-grade metamorphic basement rocks of the Precambrian Jiaobei (North China block) and Sulu (South China block) terranes during a 70-m.y.-period of lithospheric delamination, extensional core complex formation, and exhumation. The deposits are located about 20 to 200 km to the east of the continental-scale NNE-striking Tancheng-Lujiang (Tan-Lu) strike-slip fault system. They occur along a series of more regional NNE- to NE-striking brittle and ductile-brittle faults, which appear to intersect the Tan-Lu main structure to the southwest. This system of early to middle Mesozoic regional thrust faults, reactivated during Cretaceous normal motion and ore formation, tends to occur along the margins of the main Linglong batholiths or between intrusions of the two suites of granitoids. Orebodies are mainly present as quartz-pyrite veins (Linglong-type) and as stockwork veinlets and disseminated mineralization (Jiaojia-type). The two mineralization styles are transitional and may be present within the same gold deposit. The ca. 120 Ma timing of gold mineralization correlates with major changes in plate kinematics in the Pacific Basin and the onset of seismicity along the Tan-Lu fault system, with the enormous fluid volumes and associated metal being derived from sediment devolatilization above the westerly subducting Izanagi slab.


1984 ◽  
Vol 121 (6) ◽  
pp. 599-614 ◽  
Author(s):  
Wang Hongzhen ◽  
Qiao Xiufu

AbstractThe time span of the Proterozoic is taken as from 2600 to 600 Ma with subdivision boundaries at 1850 and 1050 Ma respectively, as 2600 Ma seems more appropriate for the initial Proterozoic in China, Siberia and parts of Gondwanaland, and 600 Ma is an inferred age of the Precambrian–Cambrian boundary based on recent study of the Yangtze Gorge section. The Proterozoic of China includes the Lower Proterozoic Wutaian and Hutuo-an, the Middle Proterozoic Changchengian and Jixianian and the Upper Proterozoic Qingbaikou-an and Sinian.Based mainly on tectono-sedimentary types and associations, seven stratigraphic super-regions are recognized in the Proterozoic of China and stratigraphic successions of various representative regions are shown in two tables, one for the Sinian and another for the Pre-Sinian Proterozoic. Palaeogeographic outline of the main super-regions and chronometric limit of the principal stratigraphic units are briefly discussed. Three types of stable Sinian successions are distinguished, the Yangtze type, the Quruktagh type and the Jiaoliao type, which are correlated mainly on the basis of tillite horizons and of sabelliditids and the Ediacara type of fossils. Semi-stable and mobile types of Sinian deposits in Southeast China are also briefly mentioned.The Proterozoic tectonic units of China and the nature of their boundaries are shown on a sketch map showing basement structures. Crustal sectors of continental nature are designated as continental tectonic domains, while broad and complicated crustal sectors of mainly transitional and partly oceanic nature may be called continental margin tectonic domains. The boundaries between these domains are usually the principal crustal consumption zones. On this basis, three continental domains, the North China, the South China and the Southern (Gondwana), and two continental margin domains, the Northern (Siberian–Mongolian) and the East China, are distinguished. Platforms, continental nuclei, massifs and uplifts are used to denote subdivisions within the tectonic domains. The development of aulacogens is an outstanding feature in the continental domains, especially in the Middle Proterozoic. Aulacogens may be classified into an intra-platform type and a platform margin type. Early Proterozoic aulacogens are usually brachy-axial and intermittent, and show conspicuous deformation at closure, much like a geosyncline. Thirteen aulacogens of different types are shown on the sketch map.The boundary nature of continental domains is analysed in terms of island arcs and marginal seas, and also of emplacement of granite rocks in border parts. The North China Domain was basically consolidated at around 1850 Ma and has a passive northern margin stretching from Nei Mongol to Central Tianshan, but the southern margin was active and was twice subducted by the Qinling marine realm at 1700 and 1000 Ma approximately. The Yangtze Platform was not completely consolidated until 1050 Ma BP but has a core older than 1850 Ma. A broad continental margin terrain had developed in the Jiangnan region and farther to the southeast in the Middle and Late Proterozoic. At least two island arc belts with interarc basins, an inner Fanjingshan and an outer Sibao, may be discerned in the Middle Proterozoic, and a Late Proterozoic island arc zone over 1000 km in length was developed along the southern margin of the Jiangnan Uplift, represented by the Banxi Group and equivalent strata. This kind of broad complicated continental margin tract which has a long development history may be called the open type or the West Pacific type.


1989 ◽  
Vol 26 (2) ◽  
pp. 296-304 ◽  
Author(s):  
Julie E. Gales ◽  
Ben A. van der Pluijm ◽  
Rob Van der Voo

Paleomagnetic sampling of the Lawrenceton Formation of the Silurian Botwood Group in northeastern Newfoundland was combined with detailed structural mapping of the area in order to determine the deformation history and make adequate structural corrections to the paleomagnetic data.Structural analysis indicates that the Lawrenceton Formation experienced at least two folding events: (i) a regional northeast–southwest-trending, Siluro-Devonian folding episode that produced a well-developed axial-plane cleavage; and (ii) an episode of local north-trending folding. Bedding – regional cleavage relationships indicate that the latter event is older than the regional folding.Thermal demagnetization of the Lawrenceton Formation yielded univectorial southerly and shallow directions (in situ). A fold test on an early mesoscale fold indicates that the magnetization of the Botwood postdates this folding event. However, our results, combined with an earlier paleomagnetic study of nearby Lawrenceton Formation rocks, demonstrate that the magnetization predates the regional folding. Therefore, we conclude that the magnetization occurred subsequent to the local folding but prior to the period of regional folding.While a tectonic origin for local folding cannot be entirely excluded, the subaerial nature of these volcanics, the isolated occurrence of these folds, and the absence of similar north-trending folds in other areas of eastern Notre Dame Bay suggest a syndepositional origin. Consequently, the magnetization may be nearly primary. Our study yields a characteristic direction of D = 175°, I = +43°, with a paleopole (16°N, 131 °E) that plots near the mid-Silurian track of the North American apparent polar wander path. This result is consistent with an early origin for the magnetization and supports the notion that the Central Mobile Belt of Newfoundland was adjacent to the North American craton, in its present-day position, since the Silurian.


2020 ◽  
Author(s):  
Shihong Zhang ◽  
Yangjun Gao ◽  
Qiang Ren

<p>Accumulation of the global paleomagnetic data, from both continental and oceanic plates, may suggest a true polar wander (TPW) event in Jurassic, with a rotation axis located in the present northwestern Africa, but no consensus has been reached regarding to the initiation, duration and velocity of the TPW. As one of the eastern Asian blocks, the north China block (NCB) is then located far from the rotation axis of the TPW and the plate convergence between Siberia and the Amur-NCB, known as the subduction in the Mesozoic Okhotsk-Baikal ocean, did exist. Paleogeographic changes observed of the eastern Asian blocks in Jurassic thus should contain the TPW component and plate moving component. To better estimate the influence of the TPW in the Eastern Asia blocks, we carried out a new paleomagnetic and precision U-Pb geochronological study on the middle Jurassic lavas in the NCB. Being profoundly different to the recent paleogeographic model (Yi et al., 2019, https://doi .org/10.1130/G46641.1) that suggest that the NCB experienced a large latitudinal displacement (monster-shift) responding to the TPW event between ~174 and ~157 Ma, we suggest that the NCB, as well as other blocks already connected with it, do not record any monster-shift between ~170 and ~160 Ma. The strata, ranging from 160 to 145 Ma, however, yield considerable paleomagnetic variations and need further investigation.</p>


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