On and Off the North China Craton: Where is the Archaean Keel?

Fan, W M , Zhang, H F , Baker, J , Jarvis, K E , Mason, P R D and Menzies, Martin

(2000)

Fan, W M , Zhang, H F , Baker, J , Jarvis, K E , Mason, P R D and Menzies, Martin (2000) On and Off the North China Craton: Where is the Archaean Keel?. Journal of Petrology, 41 (7).

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Abstract

Geophysical data indicate that the lithosphere beneath the North China Craton (NCC) is similar to 80 km thick with high heat flow within the craton. This is somewhat in disagreement with the presence of Archaean crustal rocks and kimberlite-hosted xenoliths that point to the existence of garnet-diamond-facies mantle beneath the craton, as recently as the Ordovician. Basalt-hosted mantle xenoliths entrained during the Cenozoic may provide a clue to Phanerozoic changes. Of particular note is the predominance of spinal-facies peridotites (75-80 km) and the paucity of garnet-facies peridotites. The model mineralogy of the spinal peridotites is similar to that observed in peridotitic xenoliths from the lower oceanic lithosphere but distinct from that of abyssal peridotites. The orthopyroxene/olivine ratio is like that of peridotites from ocean basins and tectonically active continents, and the peridotites have 'depleted' Sr and Nd isotopic ratios similar to those of oceanic basalts. The basalt-hosted xenolith data from eastern China support geophysical data in revealing the presence of thin, hot lithosphere with a similarity, over distances of several thousand kilometers, to that found beneath tectonically active continents or ocean basins. These data do not, however, allow us to constrain which of the thermo-tectonic processes (i.e. plume, extension , delamination) was responsible for the loss of the cold, thick Archaean lithospheric root (similar to 200 km) in the last 400 my. What is clear is that the pre-existent, presumably heterogeneous, Archaean lithosphere has been very effectively replaced by 'oceanic' -like mantle. The extent to which it was totally replaced is open to debate.

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This is a Submitted version
This version's date is: 7/2000
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Item TypeJournal Article
TitleOn and Off the North China Craton: Where is the Archaean Keel?
AuthorsFan, W M
Zhang, H F
Baker, J
Jarvis, K E
Mason, P R D
Menzies, Martin
Uncontrolled KeywordsNorth China Craton, mantle xenoliths, oceanic affinity, LITHOSPHERIC MANTLE BENEATH, OCEANIC UPPER-MANTLE, PERIDOTITE XENOLITHS, EASTERN CHINA, TRACE-ELEMENT, SUBCONTINENTAL LITHOSPHERE, ULTRAMAFIC XENOLITHS, ISOTOPIC SYSTEMATICS, CONTINENTAL MANTLE, ENRICHED MANTLE
DepartmentsFaculty of Science\Earth Sciences
Research Groups and Centres\Earth Sciences\Ancient and Modern Earth Systems
Research Groups and Centres\Earth Sciences\Geochemistry

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Deposited by Research Information System (atira) on 27-Jan-2013 in Royal Holloway Research Online.Last modified on 27-Jan-2013


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