Chemical and isotopic composition (Os, Pb, Nd, and Sr) of Neogene to Quaternary calc-alkalic, shoshonitic, and ultrapotassic mafic rocks from the Italian peninsula: Inferences on the nature of their mantle sources
Chemical and isotopic composition (Os, Pb, Nd, and Sr) of Neogene to Quaternary calc-alkalic, shoshonitic, and ultrapotassic mafic rocks from the Italian peninsula: Inferences on the nature of their mantle sources
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DOI：
10.1130/2007.2418(09
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
S. Conticelli;R. Carlson;E. Widom;G. Serri
中科院分区：
文献类型：
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作者：
S. Conticelli;R. Carlson;E. Widom;G. Serri
在新近纪和第四纪期间，钾质和超钾质岩浆与钾玄岩和钙碱性岩浆一起喷发，遍布意大利半岛苏拉的大部分地区。根据该火山活动的时空分布及其矿物学和成分特征，定义了三个不同的岩浆区。最西北的省份托斯卡纳岩浆省主要由不含白榴石的超钾岩（钾镁矿）、钾闪石和少量钙钙岩组成。罗马岩浆省以含白榴石岩石为主，其硅饱和度各不相同，从不饱和（白榴石和斜白榴石）到严重不饱和（卡玛闪石），但仍然存在少量的钾闪石到高钾钙碱岩石。卢卡尼亚岩浆省位于火山带的最东南边缘，主要由富迪岩（铁辉石和白榴石）和卡玛富吉岩（黄长石）组成，所有这些都含有强烈的二氧化硅饱和度。尽管存在这些岩石学差异，但新近纪意大利钾质岩和超钾质岩显示出相似的微量元素模式。高场强元素相对于大离子亲石元素的耗尽是一个共同特征。镁铁质高 MgO 岩石的 Sr、Nd 和 Pb 同位素组成范围广泛，主要与喷发的地理位置和碱金属富集有关。然而，这些样本的锇同位素组成与喷发位置并没有明显的相关性，而是取决于添加到岩浆中的“大陆地壳成分”的量。一些研究的样本与地壳污染兼容
During the Neogene and Quaternary, potassic and ultrapotassic magmas erupted in association with shoshonitic and calc-alkalic magmas across much of the Italian penin sula. On the basis of the temporal and spatial distribution of this volcanism, and its mineralogical and compositional characteristics, three different magmatic provinces have been defi ned. The northwesternmost province, the Tuscan Magmatic Province, is domi nated by leucite-free ultrapotassic rocks (lamproite), shoshonite, and minor calcalkalic rocks. The Roman Magmatic Province is dominated by leucite-bearing rocks with variable degrees of silica saturation, from undersaturated (leucitites and plagioleucitites) to strongly undersaturated (kamafugites), but minor amounts of shoshonitic to high-potassium calc-alkalic rocks are still present. The Lucanian Magmatic Province, located at the southeasternmost edge of the volcanic belt, is dominated by foiditic (hauynites and leucitites) and kamafugitic (melilitites) members, all strongly undersaturated in silica. In spite of these petrologic differences, the Neogene Italian potassic and ultrapotassic rocks display similar trace-element patterns. Depletion in high fi eld strength elements with respect to large ion lithophile elements is a common feature. Sr, Nd, and Pb iso topic compositions of mafi c high-MgO rocks range widely, relating mainly to geographic location of eruption and to enrichment in alkalies. The Os isotopic composition of these samples, however, does not clearly correlate with eruption location, but is dependent on the amount of “continental crust component” added to the magmas. Some of the studied samples are compatible with crustal contamination