Contrasting Cenozoic Lithospheric Evolution and Architecture in the Western and Eastern Sino‐Korean Craton: Constraints from Geochemistry of Basalts and Mantle Xenoliths
Contrasting Cenozoic Lithospheric Evolution and Architecture in the Western and Eastern Sino‐Korean Craton: Constraints from Geochemistry of Basalts and Mantle Xenoliths
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中朝克拉通西部与东部新生代岩石圈演化及结构的对比：来自玄武岩和地幔捕虏体地球化学的制约
DOI：
10.1086/422668
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发表时间：
2004-09
期刊：
影响因子：
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通讯作者：
Yigang Xu;Sun‐Lin Chung;Jinlong Ma;Lanbin Shi
中科院分区：
文献类型：
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作者：
Yigang Xu;Sun‐Lin Chung;Jinlong Ma;Lanbin Shi
研究了将中朝克拉通（SKC）分为东西两部分的大兴安岭-太行重力线两侧的新生代玄武岩。在SKC西部，岩浆从晚始新世-渐新世含捕虏体的碱性玄武岩演化为晚中新世-第四纪碱性和拉斑玄武岩共存。玄武岩类型的这种变化伴随着La/Yb的降低和Yb含量的增加。Sr-Nd同位素比值和不相容元素的相对丰度与当时的软流圈起源一致，尽管岩石圈地幔也可能对这些玄武岩有贡献。玄武岩地球化学的这种时间变化被解释为反映在新生代期间在西SKC的岩石圈逐渐减薄。相反的趋势是观察到的新生代玄武岩从东部SKC，这表明岩石圈增厚在这段时间内。这种增厚可能与晚白垩世-早第三纪岩浆活动高峰后的区域热衰减有关。这种对比鲜明的岩石圈过程可能反映了SKC的穿时伸展，由于晚中生代的古太平洋俯冲作用，SKC东部最初伸展，随后由早第三纪印度-欧亚碰撞引起的西SKC伸展。这意味着西SKC岩石圈地幔相对于东SKC之下的岩石圈地幔相对古老，可能是古老的岩石圈残留物和新增生地幔的混合物。这一预测的岩石圈结构与新生代玄武岩中地幔捕虏体的Sr-Nd同位素数据和最近的Re-Os年龄测定结果一致。
Cenozoic basalts from both sides of the Daxin’anling‐Taihang gravity lineament that separates the Sino‐Korean craton (SKC) into western and eastern parts have been studied. In the western SKC, magmas evolved from xenolith‐bearing alkali basalts of Late Eocene–Oligocene age to coexisting alkali and tholeiitic basalts of Late Miocene–Quaternary age. This change in basalt type is accompanied by a decrease in La/Yb and an increase in Yb content. Sr‐Nd isotopic ratios and relative abundances on incompatible elements are consistent with a prevailing asthenospheric origin, although lithospheric mantle may have also contributed to these basalts. This temporal variation in basalt geochemistry is interpreted as reflecting progressive lithospheric thinning in the western SKC during the Cenozoic. An opposite trend is observed for Cenozoic basalts from the eastern SKC, suggesting lithospheric thickening during this time period. This thickening was probably related to regional thermal decay following peak magmatism in the Late Cretaceous–Early Tertiary. Such contrasting lithospheric processes may reflect diachronous extension in the SKC, with initial extension in the eastern part owing to the Late Mesozoic paleo‐Pacific subduction and subsequent extension in the western SKC induced by the Early Tertiary Indian‐Eurasian collision. An implication is that the lithospheric mantle in the western SKC is relatively old compared with that beneath the eastern SKC, which may be a mixture of old lithospheric relicts and newly accreted mantle. This predicted lithospheric architecture is consistent with Sr‐Nd isotopic data and recent Re‐Os age determinations from mantle xenoliths included in Cenozoic basalts.