Neoarchean siliceous high-Mg basalt (SHMB) from the Taishan granite–greenstone terrane, Eastern North China Craton: Petrogenesis and tectonic implications
Neoarchean siliceous high-Mg basalt (SHMB) from the Taishan granite–greenstone terrane, Eastern North China Craton: Petrogenesis and tectonic implications
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华北克拉通东部泰山花岗绿岩地体新太古代硅质高镁玄武岩（SHMB）：岩石成因及构造意义
DOI：
10.1016/j.precamres.2013.01.017
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发表时间：
2013-05
影响因子：
3.8
通讯作者：
Touping Peng;S. Wilde;W. Fan;Bingxia Peng
中科院分区：
文献类型：
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作者：
Touping Peng;S. Wilde;W. Fan;Bingxia Peng
硅质高镁玄武岩（SHMB）是一种稀有的岩石类型，主要产于太古宙-元古代边界或其附近。它与显生宙boninites在地球化学上有一些相似之处，但也有明显的区别。SHMB的岩石成因是类似显生宙的博长岩，还是与马马岩浆岩有关，目前尚有争议。在华北克拉通东部地块的泰山花岗绿岩地体中，首次发现了新太古代巨型巨型岩石。锆石U-Pb测年结果表明，它们的侵位时间为~ 2.54Ga，与山基岩和埃达基岩的产生同时期，但晚于该区晚太古代（2.71Ga）科马长岩和科马长岩玄武岩的喷发。高MgO（>8%）、高SiO2（>52%）、Al2O3/TiO2比值（12.4 ~ 45.0），低TiO2（<0.5%）和HFSE含量，LREE和LILE富集程度强，与典型显生宙boninites相当，但存在明显的HREE亏损，缺乏u型REE模式和明显的正Zr异常。短句来源结合其相对于晚太古代科马长岩的贫Nd同位素特征（δ Nd(t=2.54Ga)=+4.42 ~ +1.05），表明这些SHMBs来源于早期玄武岩萃取的难熔贫地幔的部分熔融，并通过俯冲相关交代作用富集LILE和LREE，而非科马长岩岩浆同化-分异结晶（AFC）作用的产物。板块衍生的埃达克岩熔体可能是交代剂，以及从俯冲的海洋板块释放的少量含水流体。结合区域研究，这些岩浆的形成可能与板块回退有关，可能是由于当时大洋高原和（或）残厚岩石圈龙骨到达俯冲带所致。这一机制可能在太古宙花岗岩-绿岩带的形成过程中起了至关重要的作用，也是大陆地壳生长的重要因素，特别是在太古宙晚期。
Siliceous high-Mg basalt (SHMB) is a rare rock type that occurs mainly at or near the Archean–Proterozoic boundary. It shares some geochemical similarities with Phanerozoic boninites, but there is a clear distinction. Whether the petrogenesis of SHMB resembles that of Phanerozoic boninites or is related to the komatiitic magmatism is controversial. Neoarchean SHMBs are identified for the first time from the Taishan granite–greenstone terrane within the Eastern Block of the North China Craton (NCC). Zircon U–Pb dating indicates that they were emplaced at ∼2.54Ga, contemporaneous with the generation of sanukitoids and adakitic rocks, but later than the eruption of the Late Archean (2.71Ga) komatiites and komatiitic basalts in the area. The high MgO (>8%), high SiO2(>52%), and Al2O3/TiO2ratio (12.4–45.0), together with low TiO2(<0.5%) and HFSE contents and strong enrichment in LREE and LILE in the Taishan SHMBs are comparable with typical Phanerozoic boninites, except for distinct HREE depletion, lack of U-shaped REE patterns and conspicuous positive Zr anomalies. In conjunction with their more depleted Nd isotopic characteristics (ɛNd(t=2.54Ga)=+4.42 to +1.05) relative to Late Archean komatiites in the region, it suggests that these SHMBs were derived from partial melting of refractory depleted mantle which experienced earlier basalt extraction and was subsequently enriched in LILE and LREE by subduction-related metasomatization, rather than the products of assimilation–fractional crystallization (AFC) of komatiitic magma. A slab-derived adakitic melt was likely the metasomatizing agent, along with minor aqueous fluids released from the subducting oceanic slab. In combination with regional studies, the generation of these magmas was probably related to slab rollback, which is ascribed to the arrival of an oceanic plateau and/or residual thickened lithospheric keel at the subduction zone at that time. This mechanism might have played a crucial role in the formation of Archean granite–greenstone belts and was an important factor in continental crustal growth, particularly during the Late Archean.