菲律宾西萨马省铝土矿基本地质特征及成矿机理初探

研究认为,西萨马省铝土矿具有相似的基本地质特征与相同的成矿要素与机理,其成矿机理为：风化破碎的高铝中基性岩搬运至附近的岩溶洼地,热带海洋季风气候的湿热环境植被发育,微生物滋生,微生物腐蚀岩石产生有机酸-弱酸不断淋滤洼地堆积物,使硅质活化迁移而铁铝富集形成红土型三水铝土矿.     

萨马岛以东海域的一个次表层暖涡

通过对1988年和1989年由中国科学院海洋研究所“科学一号”船在菲律宾以东海域获得的CTD调查资料的分析,发现在萨马(Samar)岛以东海域200m层下存在着一个东西跨度约为3个经度、南北跨度约为3个纬度的次表层暖涡,本文简称为Samar暖涡。这个暖流的强度、位置及其所潜在的深度范围均有明显的年际变化。这些变化与棉兰老潜流的变化是一致的。当棉兰老潜流强时,Samar暖涡也强;反之它也弱。由此可以看出,棉兰老潜流和Samar暖涡两者之间存在着密切的关系。     

Petrological and geochemical characteristics of the Samar Ophiolite ultramafic section: implications on the origins of the ophiolites in Samar and Leyte islands,Philippines

Cretaceous ophiolites and ophiolitic fragments occur in the Samar and Leyte islands in eastern central Philippines. The Samar Ophiolite is a complete crust–mantle sequence exposed in southern Samar, whereas the Tacloban and Malitbog ophiolite complexes are, respectively, located in the northeastern and southwestern portions of the nearby Leyte island. Despite the close proximity of these islands, the genetic relationship of these ophiolites and ophiolitic complexes, if any, remains to be elucidated. We present here new petrographic and geochemical data on the harzburgites and dunites of the ultramafic section of the Samar Ophiolite. These mantle peridotites are highly depleted residues which have low modal pyroxene content, high spinel Cr# (=0.62–0.79), and slightly enriched light rare earth element abundance with depletion in Zr and Ti. Such characteristics are typical of supra-subduction zone peridotites and strongly contrast with the abyssal signatures of the Tacloban and Malitbog ophiolite complexes. The absence of a structure between these adjacent ophiolite fragments initially hints that they form a single oceanic crust. However, with our new results, we suggest other possible mechanisms that could explain the relationship of these ophiolites.