MAGMATISM IN THE SOUTH CHINA BASIN .1. ISOTOPIC AND TRACE-ELEMENT EVIDENCE FOR AN ENDOGENOUS DUPAL MANTLE COMPONENT

被引:190
作者
TU, K
FLOWER, MFJ
CARLSON, RW
XIE, GH
CHEN, CY
ZHANG, M
机构
[1] CARNEGIE INST WASHINGTON, DEPT TERR MAGNETISM, WASHINGTON, DC 20015 USA
[2] ACAD SINICA, INST GEOCHEM, CANTON 510640, PEOPLES R CHINA
[3] UNIV ILLINOIS, DEPT GEOL, URBANA, IL 61801 USA
基金
美国国家科学基金会;
关键词
D O I
10.1016/0009-2541(92)90135-R
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
A widespread episode of intraplate volcanism followed the cessation of sea-floor spreading in the South China Basin approximately 32-17 Ma BP), affecting large parts of southern China and Indochina, and penetrating oceanic basement and stranded microcontinent fragments. Geochemical data for post-spreading seamount and island lavas define suites of quartz tholeiite, olivine tholeiite, alkali olivine basalt and nephelinite, characterised by OIB-type incompatible-element distributions. High-K alkalic lavas show extreme enrichment in large-ion lithophile and high-field-strength elements relative to N-MORB. Sr-87/Sr-86 and Nd-143/Nd-144 ratios are depleted relative to bulk Earth values and partially overlap with Central Indian Ridge MORB and associated OIB. In contrast, Pb-208/Pb-204 and Pb-207/Pb-204 ratios are variable and surprisingly radiogenic for given MORB-like Pb-206/Pb-204. The isotopic and trace-element systematics confirm source heterogeneity but appear to be decoupled, implying complex mantle enrichment histories. At least two heterogeneous source components are required: a depleted but "contaminated" Indian Ocean MORB type, and an EM-2 reservoir whose isotopic composition corresponds to continent-derived sediment. Dupal-like Pb isotopic compositions (DELTA-7/4Pb=2-13, DELTA-8/4Pb=45-73) are shared by intraplate basalts from Hainan Island, the Penghu Islands, northern Taiwan and post-collision arc basalts from the Philippines. It is proposed these reflect endogenous mantle processes related to disaggregation of the south China margin rather than a northward extension of the southern hemisphere Dupal anomaly.
引用
收藏
页码:47 / 63
页数:17
相关论文
共 79 条
[1]   PALEOMAGNETIC CONSTRAINTS ON THE LATE CRETACEOUS AND CENOZOIC TECTONICS OF SOUTHEASTERN ASIA [J].
ACHACHE, J ;
COURTILLOT, V ;
BESSE, J .
EARTH AND PLANETARY SCIENCE LETTERS, 1983, 63 (01) :123-136
[2]  
[Anonymous], 1986, GEOLOGICAL SOC LONDO, DOI DOI 10.1144/GSL.SP.1986.019.01.07
[3]  
BARR SM, 1981, GEOL SOC AM BULL, V92, P508, DOI 10.1130/0016-7606(1981)92<508:GAGOLC>2.0.CO
[4]  
2
[5]  
BENAVRAHAM Z, 1973, EARTH PLANET SC LETT, V17, P365
[6]   THE GEOCHEMISTRY OF MARINE-SEDIMENTS, ISLAND-ARC MAGMA GENESIS, AND CRUST MANTLE RECYCLING [J].
BENOTHMAN, D ;
WHITE, WM ;
PATCHETT, J .
EARTH AND PLANETARY SCIENCE LETTERS, 1989, 94 (1-2) :1-21
[7]  
Boynton WV, 1984, RARE EARTH ELEMENT G, P63, DOI DOI 10.1016/B978-0-444-42148-7.50008-3
[8]   CONSTRAINTS OF SEA BEAM DATA ON CRUSTAL FABRICS AND SEAFLOOR SPREADING IN THE SOUTH CHINA SEA [J].
BRIAIS, A ;
TAPPONNIER, P ;
PAUTOT, G .
EARTH AND PLANETARY SCIENCE LETTERS, 1989, 95 (3-4) :307-320
[9]  
Briais B, 1987, EOS T AGU, V68, P1496