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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >The role of lower continental crust and lithospheric mantle in the genesis of Plio-Pleistocene volcanic rocks from Sardinia (Italy)
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The role of lower continental crust and lithospheric mantle in the genesis of Plio-Pleistocene volcanic rocks from Sardinia (Italy)

机译：下大陆壳和岩石圈地幔在撒丁岛（意大利）上新世-更新世火山岩成因中的作用

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摘要

The first comprehensive chemical and Sr-Nd-Pb isotopic data set of Plio-Pleistocene tholeiitic and alkaline volcanic rocks cropping out in Sardinia (Italy) is presented here. These rocks are alkali basalts, hawaiites, basanites, tholeiitic basalts and basaltic andesites, and were divided into two groups with distinct isotopic compositions. The vast majority of lavas have relatively high ~(87)Sr/~(86)Sr (0.7043-0.7051), low ~(143)Nd/~(144)Nd (0.5124-0.5126), and are characterised by the least radiogenic Pb isotopic composition so far recorded in Italian (and European) Neogene-to-Recent mafic volcanic rocks (~(206)Pb/~(204)Pb = 17.55 - 18.01) (unradiogenic Pb volcanic rocks, UPV); these rocks crop out in central and northern Sardinia. Lavas of more limited areal extent have chemical and Sr-ND-Pb isotopic ratios indicative of a markedly different source (~(87)Sr/~(86)Sr = 0.7031 - 0.7040; ~(143)Nd/~(144)Nd = 0.5127 - 0.5129; ~(206)Pb/~(204)Pb = 18.8 - 19.4) (radiogenic Pb volcanic rocks, RPV), and crop out only in the southern part of the island. The isotopic ratios of these latter rocks match the values found in the roughly coeval anorogenic (i.e. not related to recent subduction events in space and time) mafic volcanic rocks of Italy (i.e. Mt. Etna, Hyblean Mts., Pantelleria, Linosa), and Cenozoic European volcanic rocks. The mafic rocks of the two Sardinian rock groups also show distinct trace element contents and ratios (e.g. Ba/Nb ＞ 14, Ce/Pb = 8 - 25 and Nb/U = 29 - 38 for the UPV; Ba/NB ＜ 9, Ce/Pb = 24 - 28 and Nb/U = 46 - 54 for the RPV). The sources of the UPV could have been stabilised in the Precambrian after low amounts of lower crustal input (about 3%), or later, during the Hercynian Orogeny, after input of Precambrian lower crust in the source region, whereas the sources of the RPV could be related to processes that occurred in the late Palaeozoic-early Mesozoic, possibly via recycling of proto-Tethys oceanic lithosphere by subduction.
机译：这里介绍了在撒丁岛（意大利）种植的上新世更新世和碱性火山岩的第一个综合化学和Sr-Nd-Pb同位素数据集。这些岩石是碱性玄武岩，夏威夷岩，玄武岩，高渗玄武岩和玄武安山岩，分为具有不同同位素组成的两组。绝大多数熔岩具有较高的〜（87）Sr /〜（86）Sr（0.7043-0.7051），较低的〜（143）Nd /〜（144）Nd（0.5124-0.5126），其特征是放射源最少迄今为止，在意大利（和欧洲）的新近纪至最近的镁铁质火山岩中记录了铅同位素组成（〜（206）Pb /〜（204）Pb = 17.55-18.01）（非放射源铅火山岩，UPV）;这些岩石在撒丁岛中部和北部生长。范围较小的熔岩具有化学和Sr-ND-Pb同位素比，表明来源明显不同（〜（87）Sr /〜（86）Sr = 0.7031-0.7040;〜（143）Nd /〜（144）Nd = 0.5127-0.5129;〜（206）Pb /〜（204）Pb = 18.8-19.4）（放射性Pb火山岩，RPV），并且仅在岛的南部播种。后面这些岩石的同位素比值与意大利（如埃特纳火山，海布兰山脉，潘泰莱里亚，利诺萨山）的镁铁质火山岩的大致上等时代的成因（即与时空俯冲事件无关）相关。新生代的欧洲火山岩。两个撒丁岛岩石组的镁铁质岩石也显示出不同的痕量元素含量和比率（例如，对于UPV，Ba / Nb＞ 14，Ce / Pb = 8-25和Nb / U = 29-38; Ba / NB ＜9，对于RPV，Ce / Pb = 24-28，Nb / U = 46-54）。在少量的下地壳输入（大约3％）之后，前寒武纪的UPV来源可能已经稳定，或者在海西期造山运动中，在源区输入了前寒武纪的下地壳之后，UPV的来源已经稳定。可能与古生代晚期-中生代晚期发生的过程有关，可能是通过俯冲作用使特提斯原始岩石圈的再循环。

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