Mantle plume: the dynamic setting of the origin of Early Paleozoic mafic dykes in Ziyang,Shaanxi Province,Southern Qinling Block,China     

Chen  Xiaoqing  Liu  Shen  Feng  Caixia  Coulson  Ian M.  Fan  Yan  Tai  Kairui  Gao  Tianjing  Zhang  Siyuan 《中国地球化学学报》2020,39(3):307-325

The mafic dykes (dolerites) during the Early Paleozoic are widely spread in Langao-Ziyang, southern Qiling Block, and the investigation on these dykes are very important. Previous studies have mainly focused on the Silurian mafic dykes; however, research on the Earlier Paleozoic mafic dykes is relatively weak at present. Therefore, the overall understanding of the mantle source and genetic dynamic setting during the Early Paleozoic in this area is lacking. To study the accurate age and origin of the Early Paleozoic mafic dykes in Ziyang, southern Shaanxi Province, the mafic dykes from dabacunand Qinmingzhai were selected and the petrology, zircon U–Pb chronology, geochemistry, and Sr–Nd–Hf isotopes were studied. Analysis indicates that the mafic dykes studied are mainly composed of dolerite, and they are the products of the Early Ordovician (475.8–480.7 Ma). Furthermore, the dolerites belong to alkaline rock series, and they are characterized by enrichment in LREE, Rb, Ba, Sr, Nb, (⁸⁷Sr/⁸⁶Sr)_i = 0.7020–0.7050, ε_Nd(t) = 3.0–4.0), ε_Hf (t) = 4.5–12.1,¹⁷⁶Hf/¹⁷⁷Hf = 0.282681–0.282844. This suggests that the mafic dyke were derived from the partial melting of a depleted lithospheric mantle, and the genetic process is mainly controlled by the mantle plume based on the discussion of the genetic model. Furthermore, the genetic process experienced the separation and crystallization of olivine and clinopyroxene at the same time, with little crustal contamination.

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Viscosity of rock mass at different structural levels     

Chengzhi Qi  Chen Haoxiang  Jiping Bai  Jilin Qi  Kairui Li 《Acta Geotechnica》2017,12(2):305-320

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基于Apollo15月壤和普通球粒与碳质球粒陨石模拟实验的太空风化特征产物成因分析     

邰凯瑞  郭壮  李阳  刘燊  张鹏飞  赵斯哲  李琛  唐红  庞荣华 《地质学报》2021,95(9):2857-2865

月球、小行星等无大气行星体具有独特的反射光谱太空风化改造特征,其成因主要被归结于纳米级—亚微米级不透明颗粒等太空风化特征产物.本研究结合Apollo 返回月壤样品、普通球粒和碳质球粒陨石样品的模拟实验结果,综合分析了太空风化特征产物的来源和成因,并讨论了其可能的光谱效应.研究结果表明,np-Fe0 (纳米级单质金属铁)是铁镁硅酸盐等矿物经过微陨石轰击引起的气化沉积作用和原位还原作用形成.np-FeNi(纳米级铁镍金属)的成因主要包括FeNi金属和陨硫铁的气化沉积与冲击分散成因.np-FeNiS(纳米级铁镍金属的硫化物)和sm-FeNiS(亚微米级铁镍金属的硫化物)主要形成于陨硫铁的冲击分散过程.上述不透明颗粒是形成月球与S型小行星紫外—近红外波段光谱反射率降低、特征吸收峰减弱和连续统红移等特征的主要原因.气泡结构主要形成于层状硅酸盐等矿物在微陨石轰击过程中的挥发分逃逸,推测是含水量较高的小行星(如Bennu)紫外-近红外波段光谱反射率增加和连续统蓝移等特征的主要成因.实验结果预期对月球与小行星返回样品分析以及反射光谱的太空风化改造特征的解释提供一定的参考.  相似文献