Crust recycling in the sources of two parallel volcanic chains in Shandong, North China
Crust recycling in the sources of two parallel volcanic chains in Shandong, North China
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华北山东两条平行火山链源头的地壳循环
DOI：
10.1016/j.epsl.2010.12.026
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发表时间：
2011-02
影响因子：
5.3
通讯作者：
Hofmann AW
中科院分区：
文献类型：
--
作者：
Xu X-S;Jiang S-Y;Zeng G;Chen L-H;Hofmann AW
在许多与热点相关的海洋岛屿玄武岩源中已经记录了回收地壳成分，但在大陆玄武岩中很难识别它们，因为在大陆环境中，热点通常是模糊的，回收地壳来源很难与地壳污染区分开来。本文研究了山东两个平行的新生代火山链的主元素、微量元素和Sr-Nd-Hf同位素组成，这些火山链没有地壳污染，显示了基性下地壳再循环的明显证据。两个火山链中的Sr、Nd、Hf同位素形成了独立的二元混合阵列，这些二元混合阵列汇聚在大山火山的组成上，大山火山是一个孤立的、同位素特征最枯竭的辉石质火山。这两条链的CaO值较低，同位素富集趋势明显偏离这一共同端元。这两个趋势都偏离了正常的Sr-Nd和Hf-Nd地幔阵列，向较低的87sr /86Sr和较高的ε hf值方向发展，所有这些特征都指向一个（循环的）榴辉岩源。我们调用一个两阶段演化模型来生成这两种混合趋势的末端成员。在第一阶段，早期（晚中生代）熔融萃取使再循环基性地壳（榴辉岩）枯竭，熔融过程中石榴石的控制使残渣中的Lu/Hf相对于Sm/Nd升高。随后，这些缺乏二氧化硅的残留物被运送到更深的地幔。最后，在新生代，上涌的地幔（可能是羽流）将残余榴辉岩透镜输送到浅层软流层。由于早期熔融程度的不同，两条链下的再循环地壳成分在同位素组成上有所不同。上升流的地幔向岩石圈下方扩散，并向薄化岩石圈区域流动，如华北郯庐断裂带，在该断裂带，再循环的地壳与橄榄岩衍生的熔体发生重熔混合，形成了两种混合趋势。
Recycled crustal components have been documented for many sources of hotspot-related ocean island basalts, but they have been difficult to identify in continental basalts, because in continental settings, hotspots are often obscured and recycled crustal sources are difficult to distinguish from crustal contamination. We show major, trace element and Sr–Nd–Hf isotopic compositions for two parallel chains of Cenozoic volcanoes from Shandong Province, North China, which are free of crustal contamination and show clear evidence for recycling of mafic lower crust. Sr, Nd, and Hf isotopes in the two volcanic chains form separate binary mixing arrays, which converge on the composition of Dashan, an isolated, nephelinitic volcano with the most depleted isotopic signature. The two chains have lower CaO values and significantly diverging isotope enrichment trends from this common endmember. Both trends deviate from the normal Sr–Nd and Hf–Nd mantle array toward lower87Sr/86Sr and higher εHfvalues, all features that point to a (recycled) eclogitic source. We invoke a two-stage evolution model to generate the endmembers of these two mixing trends. In the first stage, recycled mafic crust (eclogite) is depleted by earlier (late Mesozoic) melt extraction, which elevates the Lu/Hf of the residue relative to Sm/Nd due to garnet control during melting. Subsequently, these silica-deficient residues are transported to the deeper mantle. Finally, in Cenozoic time, upwelling mantle (possibly a plume) transports lenses of residual eclogites into the shallow asthenosphere. The recycled crustal components beneath the two chains differ somewhat in isotopic composition due to different degree of the earlier melting. The upwelling mantle spreads beneath the lithosphere and flows toward regions of thinned lithosphere, e.g. the Tan–Lu Fault Zone in North China, where the recycled crust undergo remelting and mix with peridotite-derived melts to produce the two mixing trends observed.
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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
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
影响因子：
3.7
作者：
N. Sleep
通讯作者：
N. Sleep
影响因子：
0.5
作者：
T. Zack;S. Foley;G. Jenner
通讯作者：
T. Zack;S. Foley;G. Jenner
DOI：
10.1016/s1464-1895(01)00124-7
发表时间：
2001
期刊：
Physics and Chemistry of The Earth Part A-solid Earth and Geodesy
影响因子：
--
作者：
Yigang Xu
通讯作者：
Yigang Xu