Petrogenesis and characteristics of the mantle source for the Quaternary Datong basalt: Research on the major, trace elements and Sr-Nd-Pb-Hf isotopes
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DOI: 10.18654/1000-0569/2020.11.05
Abstract: 大同火山区位于大兴安岭-太行山重力梯度带西侧，所发育的第四纪玄武岩岩石地球化学特征为探索该区火山岩成因提供了重要约束，同时也为华北克拉通西部岩石圈地幔与软流圈的相互作用提供重要依据。根据火山地貌和岩性的不同，沿着北东向陈庄-许堡断裂可将大同玄武岩大致分为东、西两区，西区火山多呈锥状，以碱性玄武岩为主；东区则以溢流拉斑玄武岩为主，锥体少。镜下岩相学研究观察到大量橄榄石和单斜辉石斑晶，结合Ni、Cr两种元素随着MgO含量降低而减小，这两种矿物应是分离结晶作用下的主要产物。这些玄武岩的SiO2和（K2O+Na2O）含量分别为45.02%~53.3%和3.60%~6.53%，相对富集轻稀土元素（（La/Yb）N=5.8~31.6），并显示富集LILE（Rb、Ba、Sr正异常）以及HFSE（Nb、Ta、Zr正异常）的洋岛玄武岩（OIB）特征。根据La/Yb-Sm/Yb图解模拟计算得出大同玄武岩均是石榴石相二辉橄榄岩低程度部分熔融的结果，其中碱性玄武岩部分熔融程度约为1.5%~3%，拉斑玄武岩约为4%~8%。所研究的玄武岩有较低87Sr/86Sr（0.703302~0.705102）、较高143Nd/144Nd（0.512561~0.512963）和176Hf/177Hf（0.282922~0.283072）比值。在143Nd/144Nd-87Sr/86Sr图解上大同玄武岩落在OIB范围内；207Pb/204Pb-206Pb/204Pb和143Nd/144Nd-206Pb/204Pb图解表明它们来自PREMA和EMⅠ端元的二元混合。大同碱性玄武岩和拉斑玄武岩的地球化学特征不同可以用两点原因来解释：（1）主量与微量元素特征的差异是两种玄武岩部分熔融程度不一样形成的；（2）同位素特征表明两种玄武岩都来自软流圈亏损端元的部分熔融并存在少量岩石圈富集端元物质的加入，其差异则是加入比例不同造成的。 read more here.
Keywords: characteristics mantle; mantle source; petrogenesis characteristics; quaternary datong ... See more keywords
Implication of Mineralogy and Isotope Data on the Origin of the Permian Basic Volcanic Rocks of the Hronicum (Slovakia, Western Carpathians)
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DOI: 10.3390/min11080841
Abstract: The paper presents new geochemical data of the basic to intermediate volcanic rocks from the Hronic unit. The studied rocks are strongly altered and the primary mineral composition (clinopyroxenes, amphiboles, spinels, biotites, and plagioclases) is… read more here.
Keywords: mineralogy; implication mineralogy; volcanic rocks; mineralogy isotope ... See more keywords