RUI: Collaborative Research: Metamorphism and Deformation Associated with Late Cenozoic Strike-Slip Faulting in the Philippines

菲律宾断层是一条活跃的左旋走滑断层，几乎横贯了整个菲律宾群岛。它是世界上几个主要的走滑断层系统之一，发生在斜辐合的洋内板块边界上。这个项目和一个合作项目（EAR87-07951）将研究沿断层发生的变质岩的成因和侵位。其中一些变质岩——绿片岩相变质火山岩、角闪岩和蛇纹岩——可能是在会聚缝合带上形成的，但我们将检验至少其中一些变质岩完全是由走滑相关过程产生的假设。我们将使用构造、地质年代学和地球化学技术来确定变质岩的变形和变质历史是否与它们沿着菲律宾断层的形成相一致，而不是通过碰撞过程。现代斜辐合边缘大走滑断裂的普遍存在表明，在古代活动边缘组合中，应该存在类似的地界构造，但这种构造很少被认识到。这可能是因为人们普遍认为，收敛和走滑“缝合线”所共有的许多岩石学和构造组合只与前者有关。通过研究菲律宾沿一条活动走滑断层的变质岩的起源，我们希望建立一个框架来识别古老的弧形地体中的这种结构。

The Philippine Fault, an active, left-lateral strike-slip fault, transects almost the entire length of the Philippine Archipelago. It is one of several major strike-slip fault systems worldwide that occur at obliquely converging intra-oceanic plate boundaries. This and a collaborative project (EAR87-07951) will study the genesis and emplacement of metamorphic rocks that occur along the fault. Some of these metamorphic rocks-- greenschist-facies metavolcanics, amphibolites and serpentinites-- may be created at convergent suture zones, but we will test the hypothesis that at least some of them were generated entirely as a result of strike-slip related processes. We will use structural, geochronological and geochemical techniques to determine if the deformational and metamorphic history of metamorphic rocks is consistent with their creation along the Philippine Fault, rather than by collisional process. The common occurrence of major strick-slip faults at modern obliquely converging margins suggest that similar structures should occur as terrane boundaries in ancient active margin assemblages, but few such structures have been recognized. This may be because many petrologic and structural associations common to both convergent and strike-slip "sutures" are generally believed to be associated only with the former. By studying the origin of metamorphic rocks along an active strike-slip fault that also acts to juxtapose disparate terranes in the Philippines, we hope to establish a framework for recognizing such structures in old arc terranes.