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

菲律宾断层是一种活动的左旋走滑断层，几乎横切菲律宾群岛的整个长度。它是世界上几个主要的走滑断层系统之一，这些断层系统发生在倾斜会聚的大洋内部板块边界上。这个项目和一个合作项目(EAR87-07345)将研究沿断层出现的变质岩的成因和侵位。这些变质岩中的一些--绿片岩相变质火山岩、角闪岩和蛇纹岩--可能产生于会聚缝合带，但我们将检验这样的假设，即至少其中一些完全是走滑相关过程的结果。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产生一致，而不是通过碰撞过程。在现代斜向收敛的边缘普遍存在着主要的强滑断裂，这表明在古代活动边缘组合中应该存在类似的构造作为地体边界，但这种构造很少被识别出来。这可能是因为许多岩石学和构造组合通常被认为只与前者有关，这些组合既有会聚的，也有走滑的。通过研究沿着一条活动的走滑断裂的变质岩的起源，我们希望建立一个在旧的弧形地体中识别这种构造的框架。

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 (EAR87-07345) 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.