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首页> 外文期刊>Contributions to Mineralogy and Petrology >Geochemical and Sr-Nd-Pb isotopic characteristics of Late Cenozoic leucite lamproites from the East European Alpine belt (Macedonia and Yugoslavia)
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Geochemical and Sr-Nd-Pb isotopic characteristics of Late Cenozoic leucite lamproites from the East European Alpine belt (Macedonia and Yugoslavia)

机译：东欧高山带（马其顿和南斯拉夫）晚新生代白云岩绿岩的地球化学和Sr-Nd-Pb同位素特征

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摘要

In the East European Alpine belt, leucite-sanidine-phlogopite-olivine-bearing volcanic rocks of Late Cenozoic age occur at eight localities within the Vardar suture zone and at one locality in the Southern Carpathian fold-and-thrust belt. Most of these volcanics are characterized by high Mg# (66.6-78.6), high abundances of Ni (117-373 ppm) and Cr (144-445 ppm) as well as high primary K_2O contents (5.63-7.01 percent) and K_2O/Na_2O values (1.93=4.91). Rocks with more differentiated compositions are rare. A lamproite affinity of these rocks is apparent from their relatively low contents of Al_2O_3 (9.9-14.3 wt percent) and CaO (6.2-8.3 wt percent) in combination with high abundances of Rb (85-967 ppm), Ba (1,0274,189 ppm), Th (18.9-76.5 ppm), Pb (19-54 ppm), Sr (7741,712 ppm) and F (0.160.52 wt percent), and the general lack of plagioclase. Although eruption of the magmas took place in post-collisional extensional settings, significant depletions of Nb and Ta relative to Th and La, low TiO_2 contents (0.92-2.17 percent), low ratios of Rb/Cs, K/Rb and Ce/Pb as well as high ratios of Ba/ La and Ba/Tb suggest close genetic relationships to subduction zone processes. Whereas Sr and Nd isotope ratios show relatively large variations (~(87)Sr/~(86)Sr 0.7078-0.7105, ~(143)Nd/~(144)Nd = 0.51242-0.51215), Pb isotope ratios display a very restricted range with ~(206)Pb/~(204)Pb = 18.68-18.88 and variable but generally high DELTA 7/4 (11-18) and DELTA 8/4 (65-95) values. The observed petrographic, geochemical and isotopic characteristics are best explained by a genetic model involving preferential melting of phiogopite-rich veins in an originally depleted lithospheric mantle source, whereby the metasomatic enrichment of the mantle source is tentatively related to the addition of components from subducted sediments during consumption of Tethyan oceanic lithosphere.
机译：在东欧高山带中，晚新生代年龄的含白云石-山梨酸-金云母-橄榄石的火山岩分布在Vardar缝合带内的八个地点，以及喀尔巴阡山脉褶皱-冲断带的一个地点。这些火山大多数具有高Mg＃（66.6-78.6），高Ni（117-373 ppm）和Cr（144-445 ppm）丰度以及高K_2O含量（5.63-7.01％）和K_2O / Na_2O值（1.93 = 4.91）。成分差异更大的岩石很少见。这些岩石与铝铁矿的亲和力表现为相对较低的Al_2O_3（9.9-14.3 wt％）和CaO（6.2-8.3 wt％）以及高含量的Rb（85-967 ppm），Ba（1,0274） （189ppm），Th（18.9-76.5ppm），Pb（19-54ppm），Sr（7741712ppm）和F（0.160.52重量％），并且通常缺乏斜长石。尽管岩浆喷发发生在碰撞后的伸展环境中，Nb和Ta相对于Th和La的消耗显着，TiO_2含量低（0.92-2.17％），Rb / Cs，K / Rb和Ce / Pb的比率低Ba / La和Ba / Tb的比例很高，表明它们与俯冲带过程密切相关。 Sr和Nd同位素比显示相对较大的变化（〜（87）Sr /〜（86）Sr 0.7078-0.7105，〜（143）Nd /〜（144）Nd = 0.51242-0.51215），而Pb同位素比显示出非常严格的限制范围约为〜（206）Pb /〜（204）Pb = 18.68-18.88，并且可变，但通常具有较高的DELTA 7/4（11-18）和DELTA 8/4（65-95）值。所观察到的岩石学，地球化学和同位素特征可以通过一个遗传模型得到最好的解释，该模型涉及在原本贫瘠的岩石圈地幔源中优先富含富辉铁矿脉的熔融，因此，地幔源的交代富集作用暂时与俯冲沉积物中组分的添加有关。在消耗特提斯洋岩石圈的过程中。

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