Destruction of the North China Craton

November 26, 2012

Archean cartons are commonly underlain by a cold, thick (>200 km), isotopically enriched, and compositionally refractory lithospheric keel, and represent some of the most stable regions on our planet. However, the North China Craton (NCC), an old continental geological structure dating back 4.0 Ga, is underlain by a thin lithosphere (<100 km) and shows many signs of thermo-tectonic reactivation. this observation challenges the traditional view that lithosphere beneath cratons has always been stable supports new concept "craton destruction". now widely accepted contributed to our understanding processes intraplate magmatism generation ore-forming, continental evolution in general. 2006, chinese earth scientists sponsored by national natural science foundation china (nsfc) embarked on a major research program entitled "the destruction north craton". over past six years, they have carried out comprehensive study covering geology, geophysics, geochemistry ncc with global perspective using "natural laboratory research" scientific model. summary recent developments outcomes, taking same title nsfc's program, was published Science China, Earth Sciences, 2012, Vol. 55(10).

The scientists focused on important scientific issues relating to NCC destruction including the spatio-temporal distribution of the NCC, the structure of the deep earth and thermal-tectonic-fluid processes, correlation between the surface geology and cratonic destruction, processes and mechanisms, and the role of cratonic destruction in global geological and continental evolution. Using mobile seismic stations and in-situ isotope tracer technology, they obtained high-resolution, large-scale and multi-attribute observations, and collected and analyzed a huge amount of data. Interdisciplinary approaches based on the observations and experimental data have resulted in new evidence and insights into the destruction of the NCC and its implications for near-surface resources and global continent evolution.

Mesozoic and Cenozoic mantle-derived rocks and the peridotite xenoliths entrained in them were sampled throughout the NCC for petrological and geochemical investigations that used newly developed tracers of radiogenic isotopes (Hf and Os) and non-traditional stable isotopes (Li, Mg and Fe). These studies led to new insights into the properties of the Phanerozoic lithospheric mantle beneath the craton and the processes that modified these properties. The sub-continental lithospheric mantle of the late Mezozoic was found to be rich in water while that of the Cenozoic was highly deficient in water. It was found that the lithosphere of the NCC had thinned substantially since the Mesozoic and had undergone a significant change in composition from a refractory cratonic lithospheric mantle before the thinning to a relatively fertile "oceanic" mantle after its thinning, while during the decratonization the composition of the lithospheric mantle was very heterogeneous. It has been demonstrated that this compositional change was caused by peridotite-melt interaction. This evidence and the results of Li-Fe-Mg isotope studies infer that the reactive melts are crustal melts originating from deep continental subduction or from recycled oceanic crust and mantle-derived silicate and carbonatite melts from the asthenosphere. The formation of these melts was related to the subduction of circum-craton plates, in particular the continental Yangtze plate and the Pacific plate.

Exploring the role of craton destruction within the framework of global continental evolution, it is necessary to understand not only the nature of the lithosphere and its modification processes, but also the dynamic and tectonic system that caused craton destruction. The crust and upper mantle structures pose important constraints on the tectonic elements affecting the NCC. Since 2000, a total of 975 stations equipped with portable broadband seismometers for recording temporal data have been deployed in the NCC with an average spacing of about 10󈝻 km. Additionally, three wide-angle reflection/refraction profiles totaling 3400 km were recorded. A survey using ocean bottom seismometers (OBSs) and portable land seismometers was carried out in the Bohai region where crustal and mantle structures were studied in unprecedented detail. Significant spatial heterogeneity was observed in the NCC lithospheric thickness and crustal structure, placing constraints on the extent of the NCC destruction. This structural variance in the lithosphere indicates that parts of the NCC, especially to the east of Taihang Mountains, experienced significant destruction of the lithospheric mantle. Data relating to the upper mantle structure and the anisotropy pattern provide evidence of dynamic interactions among the subducting slab, cratonic root, and the ambient mantle beneath the NCC. These systems suggest that the destruction of the craton was dominated by the interaction between the lithospheric mantle and the asthenosphere mantle controlled by the Pacific subduction.

The surface expression of the NCC destruction includes extensional structures whereas the deep processes associated with the NCC destruction involved lithospheric transformation and thinning, as revealed by mantle- and crust-derived magmatism. The consistency between the magmatism peak period (130 Ma) and the formation ages of the metamorphic core complexes, which correspond to a period of intense extension, suggests a close linkage between the deep process and the shallow geology. The correlation between the shallow extensional activities and the Late Jurassic and Paleogene magmatism also demonstrates a close temporal-spatial relationship. The correlation between the magmatism and the surface geological response confirms that the evolution of the shallow geological features was governed by the cratonic destruction processes.

The geodynamic factor that triggered the destruction of the NCC is important to our understanding of the formation and destruction of the cratonic lithosphere in the global plate tectonic system. The findings of the NCC research project emphasizes the role of the westward subduction of the Pacific plate based on the observations of the upper mantle velocity structures, episodes of late Mesozoic magmatism, Cenozoic basaltic evolutionary trends, and subducted slab components associated with Mesozoic-Cenozoic mafic magmas. In particular, the dehydration of the subducted paleo-Pacific Plate released significant amounts of water into the overriding lithospheric mantle beneath the eastern NCC. This lowered the viscosity of the lithosphere significantly and the continental lithosphere in this region was severely weakened, which facilitated its convective removal by the underlying asthenosphere and the ultimate destruction of the NCC. Such a process is reminiscent of North America where the formation of the Cordillera belt and the partial destruction of the North American craton were related to the eastward subduction of the Farallon plate. In this sense, the craton destruction was a result of the tectonic activity of the plate margins.

The main outcomes of this study have important implications for the relationship between craton destruction and plate tectonics. Compared with typical cratons worldwide, although lithospheric thinning occurs in many other cratons, only some of them are accompanied by craton destruction. It appears that a craton that loses its lithospheric keel because of mantle pluming may preserve its inherent cratonic features. Craton destruction seems to take place only in cratons severely affected by oceanic subduction. Validating this generalization will require further studies and understanding of the physical-chemical processes that occur in the lithosphere-asthenosphere interface during the process of craton destruction.

The implementation of the NSFC's major research program on Cratonic Destruction realized multi-discipline integration of geology, geophysics, and geochemistry, provided opportunities for many young scientists, and provided a platform for promoting the contribution of Chinese earth scientists in the international community of geosciences.
See the article: Zhu R X, Xu Y G, Zhu G, et al. Destruction of the North China Craton. Sci China Earth Sci, 2012, 55: 1565, doi: 10.1007/s11430-012-4516-yContact: ZHU RiXiang

Science China Press

Related Science Articles from Brightsurf:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.

Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.

Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.

Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.

World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.

PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.

Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.

Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.

Read More: Science News and Science Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to