A noncognate relationship between megacrysts and host basalts from the Tuoyun basin, Chinese Tian Shan

Abundant kaersutite and alkali feldspar megacrysts occur together with mantle-derived and lower crustal xenoliths, including kaersutite hornblendite and syenite, in the Early Cretaceous alkaline basalts of the Tuoyun basin in the westernmost Chinese Tian Shan. Particularly, several kaersutite hornbl...

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Bibliographic Details
Published in:The Journal of Geology
Main Authors: Han, Bao-fu, Liu, Jian-bo, Zhang, Lei
Other Authors: Han, BF (reprint author), Peking Univ, Sch Earth & Space Sci, Minist Educ Key Lab Orogen Belts & Crustal Evolut, Beijing 100871, Peoples R China., Peking Univ, Sch Earth & Space Sci, Minist Educ Key Lab Orogen Belts & Crustal Evolut, Beijing 100871, Peoples R China.
Format: Journal/Newspaper
Language:English
Published: journal of geology 2008
Subjects:
CENTRAL TIEN-SHAN
ALKALI BASALTS
LITHOSPHERIC MANTLE
KERGUELEN ISLANDS
ANORTHOCLASE MEGACRYSTS
SOUTHEASTERN AUSTRALIA
IHERZOLITE XENOLITHS
PERIDOTITE XENOLITHS
SOUTHWEST TIANSHAN
COGNATE INCLUSIONS
Kerguelen
Kerguelen Islands
Online Access:https://hdl.handle.net/20.500.11897/312516
https://doi.org/10.1086/590136
Description
Summary:Abundant kaersutite and alkali feldspar megacrysts occur together with mantle-derived and lower crustal xenoliths, including kaersutite hornblendite and syenite, in the Early Cretaceous alkaline basalts of the Tuoyun basin in the westernmost Chinese Tian Shan. Particularly, several kaersutite hornblendite cumulate xenoliths have the assemblage of kaersutite + alkali feldspar + titanian mica +/- titanomagnetite +/- clinopyroxene, in which kaersutite occurs as an early-stage cumulus phase crystallized from a parental magma and alkali feldspar occurs as a late-stage intercumulus phase from the evolved magma between accumulating kaersutite grains. The megacrystic and xenolithic kaersutite has much higher Mg# values (0.70-0.96) than the host basalt (0.47-0.60). The kaersutite and alkali feldspar megacrysts have similar initial Sr-87/Sr-86 ratios (0.7032-0.7033 and 0.7035-0.7038, respectively), significantly different from their host basalts (0.7047-0.7054). Xenolithic petrography and megacrystic Sr isotope geochemistry support a common origin for the kaersutite and alkali feldspar megacrysts and preclude the precipitation of the megacrysts from their host basalts. As the fragments of kaersutite hornblendite and syenite that may have crystallized from a trachytic parental magma and its evolved magma underplated earlier in the crust-mantle transition zone, these megacrysts, together with other xenoliths, were captured and brought to the surface by the Early Cretaceous basalts. http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000259502600005&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701 Geology SCI(E) 3 ARTICLE 5 499-509 116

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