Discovery of Lower Cretaceous synmetamorphic thrust tectonics in French Lesser Antilles (La Desirade Island, Guadeloupe): Implications for Caribbean geodynamics
Discovery of Lower Cretaceous synmetamorphic thrust tectonics in French Lesser Antilles (La Desirade Island, Guadeloupe): Implications for Caribbean geodynamics
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DOI：
10.1029/2011tc002875
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发表时间：
2011-07-27
期刊：
影响因子：
4.2
通讯作者：
Balagne, M.
中科院分区：
文献类型：
--
作者：
Corsini, M.;Lardeaux, J. M.;Balagne, M.
位于瓜德罗普以东的拉德西拉德岛展示了小安的列斯群岛弧和东加勒比板块最古老的岩石。晚侏罗世蛇绿混杂岩、变玄武质枕状熔岩和放射虫岩互层、变石英闪长岩和变流纹质熔岩流组成的酸性火成杂岩和变辉长岩/微闪长岩墙群杂岩构成古老的岩浆基底。我们提出并讨论了同变质逆冲构造在这个岛上的发现。根据详细的构造分析，我们证明了两个主要的压缩事件。第一个事件（D1）的特点是普遍褶皱与逆冲发展。在该岛的东北部，发现了一个主要的逆冲断层，大阿巴克逆冲断层，它将酸性火成岩杂岩转移到蛇绿岩单元上数公里。第二次变形事件（D2）的特征是在区域尺度上观察到的与直立褶皱（F2）相关的主要普遍劈理S2，以及发育两组共轭陡倾走滑剪切带，分别为右旋130 ° N和左旋20 ° N走向。显微构造观察表明，绿片岩相变质作用与D1、D2叠加构造发育明显同期。对采自东北部火山杂岩中与D2事件有关的变形带内的两块冰长石矿物样品进行了Ar/Ar年代学研究。这些分析得到了106.2 +/- 1.7 Ma和107.2 +/- 1.8 Ma的明确一致的坪年龄。因此，缩短和增厚构造发生在早白垩世（Albian）。在现有的加勒比地球动力学框架中，我们在法属小安的列斯群岛发现的同变质逆冲构造与Aptian-Albian洋台和Andean-Cordilles东倾俯冲带之间的碰撞有关。我们的研究结果支持俯冲极性反转早白垩世。
Located east of Guadeloupe, the island of La Desirade exhibits the oldest rocks of the Lesser Antilles arc and the eastern Caribbean plate. An old magmatic basement is composed of (1) late Jurassic ophiolitic complex with meta-basaltic pillow lavas and interbedded radiolarites, (2) acid igneous complex comprising meta-quartz-diorite and meta-rhyolitic lavas flows, and (3) meta-diabasic/microdioritic dyke swarm complex. We present and discuss the discovery of synmetamorphic thrust tectonics in this island. Based on detailed structural analysis we evidenced two main compressive events. The first event (D1) is characterized by pervasive folding associated with thrust development. In the northeastern part of the island, a major thrust fault, the Grand Abaque Thrust, has been discovered which displaces for several kilometers the acid igneous complex onto the ophiolitic unit. The second deformation event (D2) is featured by a main pervasive cleavage S2 observed at the regional scale associated with upright folding (F2) and by the development of two sets of conjugated steeply dipping strike-slip shear zones, dextral 130 degrees N and sinistral 20 degrees N striking, respectively. Microstructural observations indicate that Greenschist facies metamorphism is clearly contemporaneous with the development of D1 and D2 superimposed tectonic structures. Ar/Ar geochronology was performed on two bulk of adularia minerals sampled in the northeast volcanic complex within a deformed zone related to a D2 event. These analyses yield well-defined and concordant plateau ages at 106.2 +/- 1.7 Ma and 107.2 +/- 1.8 Ma. Thus, shortening and thickening tectonics occurred during Lower Cretaceous (Albian). In the available framework of Caribbean geodynamics, the synmetamorphic thrust tectonics we discovered in the French Lesser Antilles is related to the collision between an Aptian-Albian oceanic plateau and the Andean-Cordilleran east-dipping subduction zone. Our results support subduction polarity reversal during Lower Cretaceous.