Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Chinese continental shelf of exotic origin collided with continental China 100 million years ago

22.09.2015

It has been axiomatically accepted that the basement of a continental shelf is the offshore extension and geologically part of the same continental lithosphere. While this notion may hold true in places, our analysis of the distribution of Jurassic-Cretaceous granitoids throughout the entire eastern continental China in space and time led us to the conclusion that the basement of the Chinese continental shelf (beneath East China Sea and South China Sea) is of exotic origin geologically unrelated to the continental lithosphere of eastern China.

This exotic terrane of a sizeable mass with large compositional buoyancy could be either an oceanic plateau or a micro continent, which was transported by, or along with, the paleo-Pacific plate moving in the course of NW direction and subducting beneath the eastern margin of the continental China in the Mesozoic, responsible for the granitoids with emplacement ages of ~ 190 Ma to ~ 88 Ma.


Portion of the world topographic map, highlighting the continental China and its adjacent land and seas (Google Map, 2015) to illustrate: (1) the Chinese continental shelf (basement of the East and South China Seas) to be of exotic origin; (2) arrival of the buoyant and unsubductable oceanic plateau or micro-continent at the trench jammed the trench at ~ 100 Ma; (3) the jammed trench location is shown in red dashed curve along the southeast coast of continental China although it is unclear in the north as indicated by the dashed light blue curve with question marks; (4) The yellow "drop" dots are granitoid sample locations with ages in the literature. The thick dashed purple line labeled E-W GGL approximates the East-West Great Gradient Line topographically separating the plateau to the west from the low-land hilly plain to the east.

Credit: ©Science China Press

The termination of the granitoid magmatism throughout the vast region at ~ 88 Ma manifests the likelihood of subduction cessation at this time or more likely shortly beforehand, probably at ~ 100 Ma. Subduction stops only if the trench is jammed by a sizable terrane that is compositionally buoyant and physically unsubductable. The basement of the Chinese continental shelf is understood to be such an unsubductable mass of either an oceanic plateau or micro continent as said above that collided with the eastern margin of the continental China and jammed the trench at ~ 100 Ma.

The trench jam at ~ 100 Ma led to the Pacific plate to change its course of motion from NW to NNW and to subduct beneath the predecessors of the Kamchatka and western Aleutian trenches as manifested by the age progressive Emperor Seamount Chain of the Hawaiian hotspot origin.

This Pacific plate re-orientation produced a transform boundary between the NNW moving Pacific plate and the newly accreted eastern Asian continental plate, which explains the ~ 40 Myrs' time gap of subduction related magmatism in the greater western Pacific region before the present-day western Pacific subduction began at ~ 50 Ma. Because of the large compositional contrast across this transform boundary, it may have evolved into a trench with oblique subduction until ~ 43 Ma when the Pacific plate changed its course again back to the NW direction as manifested by the ~ 43 Ma kink and age progressive Hawaiian Seamount Chain of the Hawaiian hotspot origin.

The locus (or "suture") of the jammed trench at 100 Ma is predicted to locate on the Chinese continental shelf in the vicinity of, and parallel to, the Southeast coastal line (red dashed curve in Fig. 1). The curved arc-shape of the coastal line is inherited from the pre-100 Ma arc-shaped trench, which is similar in both curvature and size to the India-Asia collision arc (red solid curve in Fig. 1). To locate the locus in the northern section in the East China Sea and Yellow Sea is not straightforward because of the recent (< 20 Ma) tectonic re-organization associated with the opening of the Sea of Japan (see the light blue dashed line with question marks in Fig. 1).

The eastern continental China in the Mesozoic can be interpreted as an active continental margin, but NOT an Andean-Type margin as treated by many. This is because the granitoids do not define "magmatic arcs" at any given time, but distribute randomly in space and time in a wide zone in excess of > 1000 km. This observation indicates the likelihood of the presence of a stagnant paleo-Pacific slab in the mantle transition-zone beneath the region as is the case in the Cenozoic, which is seismically observed at present.

The stagnant slab under heating by the ambience above and below caused the slab dehydration. This dehydration caused a sequence of processes of geodynamic and geological significance. The released water facilitated the formation of hydrous melt within and above the transition zone, which percolated through and metasomatized the upper mantle, weakened the base of the lithosphere and transformed it into asthenosphere, hence having thinned lithosphere in the Mesozoic, accompanied by melting of the being-converted "lithospheric material" to produce basaltic melt as the heat source for crustal melting and the granitoid magmatism. Such within plate magmatism was ultimately triggered by subduction and subducted slabs, and can be readily understood as a special (vs. plate boundary zone) consequence of plate tectonics.

This new understanding on the origin of the Chinese continental shelf introduces an innovative hypothesis for consideration and testing. Basement penetration drilling on ideal sites of the shelf in collaboration with industries and IODP is expected to offer the most effective testing towards a genuine understanding of the tectonic evolution of the greater western Pacific since the Mesozoic in a global tectonic context.

###

This work was supported by Durham University in the UK, Chinese NSF grants (41130314, 91014003), Chinese Academy of Sciences Innovation grant (Y42217101L), grants from Chinese National Oceanography Laboratory in Qingdao, and from regional and local authorities (Shandong Province and City of Qingdao).

See the article: Niu YL, Liu Y, Xue QQ, Shao FL, Chen S, Duan M, Guo PY, Gong HM, Hu Y, Hu ZX, Kong JJ, Li JY, Liu JJ, Sun P, Sun WL, Ye L, Xiao YY, Zhang Y (2015) Exotic origin of the Chinese continental shelf: New insights into the tectonic evolution of the western Pacific and eastern China since the Mesozoic. Science Bulletin http://link.springer.com/article/10.1007%2Fs11434-015-0891-z

Yaoling Niu | EurekAlert!

Further reports about: Chain Mesozoic continental shelf exotic lithosphere magmatism mantle

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>