"Reactive" harzburgites from Huinan, NE China: Products of the lithosphere- asthenosphere interaction during lithospheric thinning?
"Reactive" harzburgites from Huinan, NE China: Products of the lithosphere- asthenosphere interaction during lithospheric thinning?
复制标题
DOI：
10.1016/s0016-7037(02)01089-x
复制
发表时间：
2003-02
影响因子：
5
通讯作者：
Yigang Xu;M. Menzies;M. Thirlwall;Xiao-Long Huang;Y. Liu;Xiaoming Chen
中科院分区：
文献类型：
--
作者：
Yigang Xu;M. Menzies;M. Thirlwall;Xiao-Long Huang;Y. Liu;Xiaoming Chen
惠南第四纪玄武岩地幔捕虏体岩石学、微量元素和Sr-Nd同位素研究为研究粗粒硬粒岩的成因以及岩石圈减薄过程中岩石圈-软流圈相互作用的性质提供了约束。惠南哈尔茨伯基岩具有次生再结晶结构，其成分偏离残余橄榄岩的部分熔融趋势。斜辉石中稀土元素呈凸向上模式，Cr-Yb呈正相关，表明其与玄武岩熔体有高熔体/岩比的相互作用。因此，惠南辉石不是简单的部分熔融的残留物，而可能是熔融岩相互作用的结果，在这种相互作用中，渗透物通过橄榄石的沉淀优先熔化溶解辉石，将辉石转化为辉石。熔融渗透反应增强了晶界扩散动力学，形成了这些地幔岩石特有的结构。这些“反应性的”黑土最终被组成不同的小体积富含挥发物的熔体交代，这可能是由于熔体消耗反应而产生的主要黑土形成事件。惠南黑兹伯尔岩的形成很可能与大陆岩石圈的热构造侵蚀同时发生。温度测量表明岩石圈减薄与寄主玄武岩喷发之间存在相对较长的时间间隔，这与中国东部岩石圈减薄可能在晚白垩世达到顶峰的观点一致。
Petrologic, trace element and Sr-Nd isotopic studies of mantle xenoliths in Quaternary basalts from Huinan, NE China provide constraints on the origin of coarse-grained harzburgites and the nature of lithosphere-asthenosphere interaction during lithospheric thinning. The Huinan harzburgites have a secondary recrystallized texture and their composition deviates from the partial melting trend of residual peridotites. The convex-upward REE pattern and a positive Cr-Yb correlation in clinopyroxene imply an interaction with basaltic melts at a high melt/rock ratio. The Huinan harzburgites are therefore not simple residues of partial melting, but likely resulted from melt-rock interaction during which the percolating melts preferentially dissolved pyroxenes by precipitation of olivine, transforming lherzolite to harzburgite. The melt percolation-reaction enhanced grain boundary diffusion kinetics, and gave rise to the characteristic texture of these mantle rocks. These “reactive” harzburgites were eventually metasomatized by compositionally distinct small volume volatile-rich melts, which may be derived from the main harzburgite-forming event as a result of melt-consuming reaction. Most likely the formation of the Huinan harzburgites was coeval with thermo-tectonic erosion of the continental lithosphere by upwelling asthenospheric melts. Thermometric considerations suggest a relatively long time interval between lithospheric thinning and eruption of the host basalts, consistent with the contention that lithospheric thinning in eastern China may have peaked in the late Cretaceous.