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Geochemistry of post-spreading magma...

Tu, Kan.

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Geochemistry of post-spreading magmatism in the South China Basin: Isotopic evidence for an endogenous dupal component.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Geochemistry of post-spreading magmatism in the South China Basin: Isotopic evidence for an endogenous dupal component./
Author:	Tu, Kan.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 1991,
Description:	139 p.
Notes:	Source: Dissertation Abstracts International, Volume: 52-06, Section: B, page: 2959.
Contained By:	Dissertation Abstracts International52-06B.
Subject:	Geochemistry. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9132314

Geochemistry of post-spreading magmatism in the South China Basin: Isotopic evidence for an endogenous dupal component.
Tu, Kan.

Geochemistry of post-spreading magmatism in the South China Basin: Isotopic evidence for an endogenous dupal component. - Ann Arbor : ProQuest Dissertations & Theses, 1991 - 139 p.

Source: Dissertation Abstracts International, Volume: 52-06, Section: B, page: 2959.

Thesis (Ph.D.)--University of Illinois at Chicago, 1991.

A widespread episode of intraplate volcanism followed the cessation of sea floor spreading in the South China Basin ($<$15 Ma), affecting large parts of southern China and Indochina, and penetrating oceanic basement and microcontinent fragments. Geochemical data for post-spreading seamount and island lavas define suites of quartz tholeiite, olivine tholeiite, alkali olivine basalt and nephelinite, characterized by Ocean Island Basalt (OIB) type incompatible element distributions. High-K variants show extreme enrichment in both low and high field strength elements relative to Mid-Ocean Ridge Basalt (MORB) and alkaline arc basalt. $\sp{87}$Sr/$\sp{86}$Sr and $\sp{143}$Nd/$\sp{144}$Nd ratios are depleted relative to bulk earth values and partially overlapped with Central Indian Ridge MORB and associated OIB. In contrast, $\sp{208}$Pb/$\sp{204}$Pb and $\sp{207}$Pb/$\sp{204}$Pb ratios are variable and surprizingly radiogenic for given MORB-like $\sp{206}$Pb/$\sp{204}$Pb. Hainan Island basalts, erupted in a quasi-oceanic pull-apart trough at the northern edge of the South China Basin, show similar OIB-type trace element and Sr-Nd isotope patterns to those of the South China Basin, but have "high angle" $\sp{207}$Pb arrays and high "threshold" $\sp{208}$Pb values, suggesting an aging high Th/U contaminant. At least two heterogeneous source components are required: a depleted but "contaminated" Indian Ocean MORB type, and an enriched mantle (EMII) reservoir whose isotopic composition corresponds to continent-derived sediment. Dupal-like Pb isotopic compositions are shared by basalts from Taiwan, the Penghu Islands, ophiolites from the Philippines and Eastern Taiwan, and pre-collision arc basalts from the Philippines, appearing to define a circum-South China Basin Dupal domain. It is proposed that these reflect endogenous mantle processes related to disaggregation of the south China margin rather than an extension of the southern hemisphere Dupal anomaly. In the probable absence of a mantle plume, decompression melting of subcontinental lithosphere mantle may result from lithosphere stretching, as a regional response to the Indo-Eurasian collision.Subjects--Topical Terms:

539092
Geochemistry.

Geochemistry of post-spreading magmatism in the South China Basin: Isotopic evidence for an endogenous dupal component.
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245 1 0 $a Geochemistry of post-spreading magmatism in the South China Basin: Isotopic evidence for an endogenous dupal component.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 1991
300 $a 139 p.
500 $a Source: Dissertation Abstracts International, Volume: 52-06, Section: B, page: 2959.
502 $a Thesis (Ph.D.)--University of Illinois at Chicago, 1991.
520 $a A widespread episode of intraplate volcanism followed the cessation of sea floor spreading in the South China Basin ($<$15 Ma), affecting large parts of southern China and Indochina, and penetrating oceanic basement and microcontinent fragments. Geochemical data for post-spreading seamount and island lavas define suites of quartz tholeiite, olivine tholeiite, alkali olivine basalt and nephelinite, characterized by Ocean Island Basalt (OIB) type incompatible element distributions. High-K variants show extreme enrichment in both low and high field strength elements relative to Mid-Ocean Ridge Basalt (MORB) and alkaline arc basalt. $\sp{87}$Sr/$\sp{86}$Sr and $\sp{143}$Nd/$\sp{144}$Nd ratios are depleted relative to bulk earth values and partially overlapped with Central Indian Ridge MORB and associated OIB. In contrast, $\sp{208}$Pb/$\sp{204}$Pb and $\sp{207}$Pb/$\sp{204}$Pb ratios are variable and surprizingly radiogenic for given MORB-like $\sp{206}$Pb/$\sp{204}$Pb. Hainan Island basalts, erupted in a quasi-oceanic pull-apart trough at the northern edge of the South China Basin, show similar OIB-type trace element and Sr-Nd isotope patterns to those of the South China Basin, but have "high angle" $\sp{207}$Pb arrays and high "threshold" $\sp{208}$Pb values, suggesting an aging high Th/U contaminant. At least two heterogeneous source components are required: a depleted but "contaminated" Indian Ocean MORB type, and an enriched mantle (EMII) reservoir whose isotopic composition corresponds to continent-derived sediment. Dupal-like Pb isotopic compositions are shared by basalts from Taiwan, the Penghu Islands, ophiolites from the Philippines and Eastern Taiwan, and pre-collision arc basalts from the Philippines, appearing to define a circum-South China Basin Dupal domain. It is proposed that these reflect endogenous mantle processes related to disaggregation of the south China margin rather than an extension of the southern hemisphere Dupal anomaly. In the probable absence of a mantle plume, decompression melting of subcontinental lithosphere mantle may result from lithosphere stretching, as a regional response to the Indo-Eurasian collision.
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650 4 $a Geophysics. $3 535228
650 4 $a Mineralogy. $3 516743
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710 2 $a University of Illinois at Chicago. $3 1020478
773 0 $t Dissertation Abstracts International $g 52-06B.
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791 $a Ph.D.
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793 $a English
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