Geochemical constraints on the nature of mantle source for Cenozoic continental basalts in east-central China
Geochemical constraints on the nature of mantle source for Cenozoic continental basalts in east-central China
复制标题
中国中东部新生代陆相玄武岩地幔源性质的地球化学约束
DOI：
10.1016/j.lithos.2011.05.007
复制
发表时间：
2011-08
期刊：
影响因子：
3.5
通讯作者：
Zheng, Yong-Fei
中科院分区：
文献类型：
--
作者：
Zhang, Jun-Jun;Zhao, Zi-Fu;Wang, Yan;Zheng, Yong-Fei
对中国中东部新生代大陆玄武岩的全岩主量元素和微量元素以及 Sr-Nd-Hf-Pb 和 O 同位素进行了分析。对所有结果的综合解释用于对地幔源的性质进行严格限制。玄武岩的岩石化学性质呈碱性，微量元素分布呈 OIB 状。它们的放射性同位素组成相对贫乏，与新生代 MORB 类似。但它们的ΔNb值、Nb/U、Ce/Pb比值与MORB型地幔源区不一致。它们具有较高的 Fe/Mn 比、几乎恒定的 Nb/Ta 比以及相对较高的橄榄石斑晶 Ni 含量。一些单斜辉石斑晶的 δ18O 值比正常地幔衍生的单斜辉石低。综上所述，脱水低δ18O大洋玄武岩参与了陆相玄武岩的地幔源区，而缺硅辉石岩是除橄榄岩之外的最佳物源岩性候选物。因此，脱水的大洋变玄武岩被认为在俯冲过程中产生了低 δ18O 埃达克岩熔体，其交代了上覆的地幔楔橄榄岩，生成了同位素贫乏但易发生类似 OIB 玄武岩岩浆作用的幼年次大陆岩石圈地幔 (SCLM)。熔体-橄榄岩反应被认为发生在大陆岩石圈下方洋壳低角度俯冲期间，将地幔楔橄榄岩转变为辉石岩。因此，大陆玄武岩的地幔源区由辉石岩-橄榄岩混合物组成，新生代大陆裂谷导致岩石圈-软流圈热边界部分熔融，形成碱性玄武岩浆。因此，洋壳熔体与幔楔橄榄岩之间的相互作用是年轻SCLM源形成的关键，而大陆玄武岩的成分提供了不同SCLM源相对于板块构造体系的快照。
Cenozoic continental basalts from east-central China were analyzed for their whole-rock major and trace elements as well as Sr–Nd–Hf–Pb and O isotopes. An integrated interpretation of all the results is used to place tight constraints on the nature of mantle source. The basalts are alkaline in lithochemistry and show the OIB-like patterns of trace element distribution. Their radiogenic isotopic compositions are relatively depleted, similar to those of Cenozoic MORB. But their ΔNb values, and Nb/U and Ce/Pb ratios are inconsistent with the MORB-type mantle source. They have high Fe/Mn ratios, almost constant Nb/Ta ratios, and relatively high Ni contents of olivine phenocrysts. Some clinopyroxene phenocrysts have lower δ18O values than normal mantle-derived clinopyroxenes. Taken all these observations together, it appears that the dehydrated low δ18O oceanic basalt was involved in the mantle source of continental basalts, and the silica-deficient pyroxenite is the best candidate for source lithology in addition to peridotite. Thus, the dehydrated oceanic metabasalt is assumed to produce low δ18O adakitic melts during subduction, which metasomatized the overlying mantle-wedge peridotite to generate the juvenile subcontinental lithospheric mantle (SCLM) that is isotopically depleted but fertile for OIB-like basaltic magmatism. The melt–peridotite reaction is assumed to occur during low-angle subduction of the oceanic crust beneath the continental lithosphere, converting the mantle-wedge peridotite to the pyroxenite. Thus the mantle source of continental basalts is composed of pyroxenite–peridotite mixtures, whose partial melting at the lithosphere–asthenosphere thermal boundary due to continental rifting in the Cenozoic gave rise to the alkalic basaltic magmas. Therefore, the interaction between the oceanic crustal-derived melt and the mantle-wedge peridotite is a key to formation of the juvenile SCLM source, and the composition of continental basalts provides a snapshot of different SCLM sources with respect to the regime of plate tectonics.
登录
查看更多内容
影响因子：
3.9
作者：
H. Zou;A. Zindler;Xi‐sheng Xu;Q. Qi
通讯作者：
H. Zou;A. Zindler;Xi‐sheng Xu;Q. Qi
DOI：
10.1016/0168-9622(86)90054-0
发表时间：
1986
期刊：
Chemical Geology: Isotope Geoscience Section
影响因子：
--
作者：
Z. Peng;R. Zartman;K. Futa;D. G. Chen
通讯作者：
Z. Peng;R. Zartman;K. Futa;D. G. Chen
DOI：
10.1016/0012-821x(86)90185-8
发表时间：
1986-09
期刊：
--
影响因子：
--
作者：
Z. Palacz;Andrew D. Saunder
通讯作者：
Z. Palacz;Andrew D. Saunder
影响因子：
5.3
作者：
S. S. Schmidberger-S.;A. Simonetti;D. Francis
通讯作者：
S. S. Schmidberger-S.;A. Simonetti;D. Francis
DOI：
--
发表时间：
2007
期刊：
--
影响因子：
--
作者：
G. Foulger;D. Jurdy
通讯作者：
G. Foulger;D. Jurdy