Mineralogy and geochemistry of latest Miocene deposits in the Tyrrhenian Sea@en

Late Miocene sediments from ODP Sites 652 and 654, drilled on the Sardinian margin in the Western Tyrrhenian Sea, are investigated through mineralogical, micromorphological, geochemical, and microgeochemical analyses. Clay associations appear to be little controlled by conditions of deposition, and largely depend on pre- and post-depositional conditions. The sedimentary series from Central Mediterranean gives very different geodynamic information, according to the sector considered. While relatively stable conditions, like those encountered in Caltanissetta Basin, Sicily, favor the mineralogical expression of warm-temperate and subarid Messinian climate, the Eastern Sardinia margin (Site 654) clay suites mainly reflect the transition from tectonically active to relaxed conditions. The series deposited at the foot of the same margin above a thinner crust (Site 652) experienced the effects of burial diagenesis, enhanced by strong geothermal gradient.针对第勒尼安海西部撒丁岛边缘钻取的大洋钻探计划（Ocean Drilling Program, ODP）652与654站位的晚中新世（Late Miocene）沉积物，本研究通过矿物学、微形貌学（micromorphological）、地球化学与微地球化学（microgeochemical）分析手段开展系统探究。黏土组合的形成几乎不受沉积环境的直接制约，而主要受控于沉积前与沉积后环境条件。依据所关注的区域差异，地中海中部的沉积序列可提供截然不同的地球动力学（geodynamic）信息。尽管西西里岛卡尔塔尼塞塔盆地这类相对稳定的沉积环境，更能体现暖温带亚干旱的墨西拿期（Messinian）气候的矿物学特征，但撒丁岛东部边缘（654站位）的黏土组合主要反映了从构造活跃到构造松弛的环境转变过程。赋存于地壳厚度较薄的同一边缘斜坡脚下的沉积序列（652站位），则受到了由强地热梯度（geothermal gradient）强化的埋藏成岩作用（burial diagenesis）影响。