The Zambales complex: gravity anomalies and a very strange ophiolite     

John MILSOM  Jenny BARRETTO  Jonathan AITCHISON 《地球学报》2009,30(Z1):37-37

In common with most of the larger ophiolite bodies that were emplaced during the Cenozoic and late Mesozoic and which have experienced relatively little post-emplacement disruption or metamorphism, the Zambales Ophiolite Complex (ZOC) of western Luzon (northern Philippines) is associated with very large gravity anomalies. Worldwide and in the ZOC, peak to trough amplitudes of more than 100 mGal are common and amplitudes in excess of 200 mGal are not unknown  相似文献   

Geology, Geochemistry and Chromite Mineralization Potential of the Amnay Ophiolitic Complex, Mindoro, Philippines     

Graciano P. Yumul Jr  Ferdinand T. Jumawan    Carla B. Dimalanta 《Resource Geology》2009,59(3):263-281

The Amnay Ophiolitic Complex in Mindoro, the Philippines, is considered an emplaced Cenozoic South China Sea oceanic lithosphere as a result of the collision between the Palawan microcontinental block and the Philippine mobile belt. Middle Oligocene sedimentary rocks intercalated with dominantly MORB-like pillow lavas and volcanic flows suggest the generation of this ophiolite complex in an intermediate spreading ridge within a back-arc basin setting. The volcanic rock suite geochemistry also manifests a slab component suggesting that it is a supra-subduction zone ophiolite. Petrography of the gabbros shows a plagioclase-clinopyroxene crystallization order consistent with a back-arc basin setting. Spinel and pyroxene geochemistry shows that the lherzolites and aluminous-spinel harzburgites are products of low degrees of partial melting. The chromitites hosted by the harzburgites could have not been associated with the MORB-like volcanic suites, gabbros, lherzolites and aluminous-spinel harzburgites. The chromitites are products of mantle sources that have undergone higher degrees of partial melting that would have involved the presence of water. The study of this ophiolitic complex gives us a glimpse of the characteristics of the South China Sea.  相似文献   

A prehistoric lahar-dammed lake and eruption of Mount Pinatubo described in a Philippine aborigine legend     

Kelvin S. Rodolfo  Jesse V. Umbal 《Journal of Volcanology and Geothermal Research》2008

The prehistoric eruptions of Mount Pinatubo have followed a cycle: centuries of repose terminated by a caldera-forming eruption with large pyroclastic flows; a post-eruption aftermath of rain-triggered lahars in surrounding drainages and dome-building that fills the caldera; and then another long quiescent period. During and after the eruptions lahars descending along volcano channels may block tributaries from watersheds beyond Pinatubo, generating natural lakes. Since the 1991 eruption, the Mapanuepe River valley in the southwestern sector of the volcano has been the site of a large lahar-dammed lake. Geologic evidence indicates that similar lakes have occupied this site at least twice before. An Ayta legend collected decades before Mount Pinatubo was recognized as a volcano describes what is probably the younger of these lakes, and the caldera-forming eruption that destroyed it.  相似文献   

A detailed magnetic and mineralogical study of self-reversed dacitic pumices from the 1991 Pinatubo eruption (Philippines)     

M. Bina  J. C. Tanguy  V. Hoffmann  M. Prévot  E. L. Listanco  R. Keller  K. Th. Fehr  A. T. Goguitchaïchvili  & R. S. Punongbayan 《Geophysical Journal International》1999,138(1):159-178

  相似文献   

Propagators and ridge jumps in a back‐arc basin,the West Philippine Basin     

Anne Deschamps  Ryuichi Shinjo  Takeshi Matsumoto  Chao‐Shing Lee  Serge E. Lallemand  Shiguo Wu  Scientific party of KR‐  KR‐ cruises 《地学学报》2008,20(4):327-332

We explore the tectono‐magmatic processes in the western West Philippine Basin, Philippine Sea Plate, using bathymetric data acquired in 2003 and 2004. The northwestern part of the basin formed through a series of northwestward propagating rifts. We identify at least five sequences of propagating rifts, probably triggered by mantle flow away from the mantle thermal anomaly that is responsible for the origin of the Benham and Urdenata plateaus. Gravitational forces caused by along‐axis topographic gradient and a ～30° ridge reorientation appear to also be driving the rift propagations. The along‐axis mantle flow appears to be reduced and deflected along the Luzon‐Okinawa fracture zone, because the spreading system remained stable west of this major fault zone. North‐east of the Benham plateau, a left‐lateral fracture zone has turned into a NE–SW‐trending spreading axis. As a result, a microplate developed at the triple junction.  相似文献   

Corruption begets pollution     

Yap HT 《Marine pollution bulletin》2006,52(10):1121-1122

  相似文献   

Effects of multiple perturbations on the survivorship of fragments of three coral species     

Dizon RM  Yap HT 《Marine pollution bulletin》2006,52(8):928-934

Fist-sized fragments of Porites cylindrica, Porites rus and Pavona frondifera were deployed in single-species (P. cylindrica) and mixed-species (all three) plots in a shallow reef area in the northwestern Philippines. After 6 months, the corals in half of the plots were broken into smaller pieces to simulate an episodic physical disturbance. The survival of all corals was monitored from March 2000 to July 2001 during which the corals experienced 2 typhoons and episodes of algal overgrowth. For both intact and broken treatments, there was significantly higher survival in the mixed-species plots than in the single-species treatments. Fragment mortality varied between disturbances of varying frequencies and magnitudes, namely: one-time fragmentation stress, seasonal overgrowth by cyanobacteria and macroalgae, short-term (1 day) and long-term (more than 1 week) burial. The mixed-species assemblages had higher fragment survivorship than the monospecific assemblages during small-scale perturbations (e.g., algal overgrowth), but not in the face of subsequent, larger scale disturbances. This study emphasizes that coral responses to disturbance are both species- and context-specific.  相似文献   

Grain size, areal thickness distribution and controls on sedimentation of the 1991 Mount Pinatubo tephra layer in the South China Sea     

Martin G. Wiesner  Andreas Wetzel  Sandra G. Catane  Eddie L. Listanco  Hannah T. Mirabueno 《Bulletin of Volcanology》2005,67(5):490-495

  相似文献   

Transition from common to private coasts: Consequences of privatization of the coastal commons     

Reniel B. Cabral  Porfirio M. Aliño 《Ocean & Coastal Management》2011,54(1):66-74

Privatization is often viewed to provide positive stimulus for the economy that can lead to the betterment of society. But when the appropriate governance systems are not functionally in place, the unwanted effects of privatization can have deleterious consequences. This paper highlights the consequences of undesirable privatization and the emergent unwanted privatization tendencies of the coastal commons, particularly in the developing countries such as the Philippines. The lack of coherent policies, standards, and weak enforcement of policies in leasing the coastal commons (e.g. various unregulated aquaculture) in the Philippines in particular, have resulted to alarming displacement, deprivation and marginalization of fishing and farming communities and have degraded many coastal zone areas. In addition, poorly planned coastal tourism and housing development projects in the foreshore areas, inappropriate reclamation of coastal areas, illegal usurpation of indigenous people’s rights over ancestral domain areas, and conversion of fishing and fish farming zones into ecotourism zones further aggravated this scenario. Equitable access to resources is of paramount importance to afford concerned stakeholders greater participation in terms of developing greater capacity for coastal communities to engage and demand for improved coastal governance - an important facet of public administration often identified as one of the challenges in managing the commons. Co-management with an Ecosystem-Based Management approach as core operational mechanism provides opportunities to enhance policy formulation and implementation, secure community safety nets, and facilitate the creation of a level-playing environment that help to prevent the unwanted effects of privatization.  相似文献   

Sculpting the Philippine archipelago since the Cretaceous through rifting,oceanic spreading,subduction, obduction,collision and strike-slip faulting: Contribution to IGMA5000     

《Journal of Asian Earth Sciences》2013

The Philippine archipelago resulted from a complex series of geologic events that involved continental rifting, oceanic spreading, subduction, ophiolite obduction, arc-continent collision, intra-arc basin formation and strike-slip faulting. It can be divided into two tectono-stratigraphic blocks, namely; the Palawan–Mindoro Continental Block (PCB) and the Philippine Mobile Belt (PMB). The PCB was originally a part of the Asian mainland that was rifted away during the Mesozoic and drifted in the course of the opening of the South China Sea (SCS) during Late Paleogene. On the other hand, the PMB developed mainly from island arcs and ophiolite terranes that started to form during the Cretaceous. At present, the PMB collides with the PCB in the Visayas in the central-western Philippines. This paper discusses recent updates on Philippine geology and tectonics as contribution to the establishment of the International Geologic Map of Asia at 1:5 M scale (IGMA5000).  相似文献