Ophiolitic detritus in Cretaceous clastic formations of the Dinarides (NW Croatia): evidence from Cr-spinel chemistry
Ophiolitic detritus in Cretaceous clastic formations of the Dinarides (NW Croatia): evidence from Cr-spinel chemistry
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Dinarides（克罗地亚西北部）白垩纪碎屑岩地层中的蛇绿岩碎屑：来自铬尖晶石化学的证据
DOI：
10.1007/s00531-008-0306-3
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发表时间：
2009
影响因子：
2.3
通讯作者：
L. Babić
中科院分区：
文献类型：
--
作者：
Borna Lužar;T. Mikes;H. von Eynatten;L. Babić
铬尖晶石是克罗地亚西北部Dinarides地区白垩纪同造山沉积建造砂岩中常见的重矿物。这些岩石孤立地出现在萨格勒布附近的梅德韦德尼察、伊万什契察、乌姆贝拉克和萨莫博尔山脉的隆起基底单元中。在这一地区，Dinarides早期阿尔卑斯山演化的证据是模糊的，因为强烈的构造历史导致的前第三纪构造地层单位的强烈肢解，以及由于潘诺尼亚盆地的广泛沉积覆盖。Oštrc组碎屑铬尖晶石的电子探针分析表明，早白垩世蛇绿岩源区主要由辉绿橄榄岩和伴生堆晶岩组成，它们发育于超俯冲带环境。具有相同化学特征的铬尖晶石的供应一直占主导地位，直到白垩纪末，这表明同一蛇绿岩带的暴露残余物持续通过白垩纪和/或回收是显着的。与北方石灰质阿尔卑斯山和跨多瑙河中央山脉报告的数据相似，这意味着在早白垩世期间，相当广泛的方辉橄榄岩蛇绿岩带可能沿着亚得里亚海边缘延伸。从早白垩世到晚白垩世，Cr#的变化略有增加的趋势，这表明随着白垩纪构造演化的进行，源区变得更加不均匀。在铬尖晶石组合物的差异，在两个同时代的最新白垩纪地层是符合现有的数据重矿物的比例，一起确定对比腹地地质这些地层，并强烈建议同时代存在的两个独立的盆地。
Cr-spinel is a common heavy mineral in the sandstones of Cretaceous synorogenic sedimentary formations of the NW Dinarides, Croatia. The rocks occur in isolated exposures in the uplifted basement units of Medvednica, Ivanščica, Žumberak and Samobor Mountains near Zagreb. In this area, evidence of the early Alpine evolution of the Dinarides is obscured due to strong dismemberment of pre-Tertiary tectonostratigraphic units resulting from an intense tectonic history, as well as due to the widespread sedimentary cover of the Pannonian Basin. Electron microprobe analyses of detrital Cr-spinels from the Oštrc Formation reveal that in the Early Cretaceous the ophiolitic source area was predominantly composed of harzburgite peridotites and associated cumulate rocks, which developed in a supra-subduction zone setting. The supply of Cr-spinels with the same chemical signature remained dominant until the end of the Cretaceous, suggesting that exposed remnants of the same ophiolite belt persisted through the Cretaceous and/or that recycling was significant. Similarities with data reported from the Northern Calcareous Alps and the Transdanubian Central Range imply that a rather extensive harzburgitic ophiolite belt probably extended along the Adriatic margin during the Early Cretaceous. A slight trend of increasing variation in the Cr# is observed from the Early to the latest Cretaceous, suggesting that the source areas became more heterogeneous with the ongoing Cretaceous tectonic evolution. Differences in Cr-spinel compositions in two contemporaneous latest Cretaceous formations are well in line with existing data on heavy mineral proportions, which together identify contrasting hinterland geology for these formations and strongly suggest the coeval existence of two separate basins.