Gravity variations along the Southeast Bohol Ophiolite Complex (SEBOC), Central Philippines: Implications on Ophiolite Emplacement

Barretto, Jenny Anne L.; Dimalanta, Carla B.; Yumul, Graciano P.

doi:10.1111/j.1440-1738.2000.00303.x

Cited by 7 publications

(9 citation statements)

References 14 publications

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“…Slightly lower anomalies (15 mGals) were observed over the Panguiranan Chert. The low gravity anomaly of the BOC is comparable to Bouguer anomalies of other dismembered ophiolites such as the Marum ophiolite complex in Papua New Guinea, East Halmahera ophiolite in Indonesia, and the South East Bohol, Cebu and Antique ophiolite complexes in Central Philippines (e.g., Milsom 1984;Milsom et al 1996;Barretto et al 2000;. It also suggests that the ophiolite is not deeply rooted in the mantle.…”

Section: Geophysicsmentioning

confidence: 60%

“…Previous works on Central Philippine ophiolites and ophiolitic sequences show these discrete crust-mantle slices to be of supra-subduction affinity [e.g., Tacloban, Samar, Malitbog, Southeast Bohol, Cebu] (e.g., Barretto et al 2000;Faustino et al 2003;Tamayo et al 2004;Suerte et al 2005;. Apart from the Oligocene Amnay Ophiolite in Mindoro which has the ocean island basalts (OIB) or enriched mid-oceanic ridge basalts (EMORB) component in addition to its transitional island arc tholeiite -N-MORB geochemistry (Jumawan et al 1998;Perez et al 2013), the general observation is that ophiolites in the central Philippines were generated with variable degrees of subduction influences (e.g., Faustino et al 2006;Dimalanta et al 2009;Yumul et al 2013).…”

Section: Implications For Tectonic Settingsmentioning

confidence: 99%

“…Based on geophysical observations, most ophiolites in the region are allochthonous and shallow-rooted. Gravity and magnetic investigations show that the SEBOC, Sibuyan and Tacloban ophiolites were emplaced as thin slivers of oceanic crust (e.g., Barretto et al 2000;Dimalanta et al , 2009. Their occurrence along the peripheries of islands as highly-dismembered and often poorly-preserved units suggests complex emplacement histories consistent with emplacement along subduction zones.…”

Section: Implications For Tectonic Settingsmentioning

confidence: 99%

“…Florendo (1987) suggests the existence of an Early Cretaceous subduction in the Central Philippines followed by back-arc spreading to the east. Recent isotopic ages and geochemical data suggest that the ophiolite and ophiolitic units in the eastern and central Philippines were formed from a single oceanic basin, called the proto-Philippine Sea Plate (e.g., Florendo 1987;Maac and Ylade 1988;Barretto et al 2000; A left lateral strike-slip fault traverses the archipelago. The study area is highlighted in a box.…”

Section: Introductionmentioning

confidence: 99%

“…(c) General comparison of lithology, age and geochemical characteristics of the ophiolites in the Central Philippines. Numbered references are as follows: (1) Rangin et al (1991), (2) Tamayo et al (2001), (3) Barretto et al (2000), (4) Faustino et al (2006), (5) Wolcke and Scholz (1988), (6) Hashimoto (1981), ( Suerte et al 2005;. The delineation of the Balud Ophiolitic Complex (BOC) in southwest Masbate, Central Philippines gives additional information that hopefully would contribute to the reconstruction and understanding of the evolution of the Philippines and this part of Southeast Asia.…”

Section: Introductionmentioning

confidence: 99%

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Geochemical and Geophysical Characteristics of the Balud Ophiolitic Complex (BOC), Masbate Island, Philippines: Implications for its Generation, Evolution and Emplacement

Manalo¹,

Dimalanta²,

Faustino-Eslava³

et al. 2015

Terr. Atmos. Ocean. Sci.

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This paper presents the first field, geochemical and geophysical information on the recently recognized Early Cretaceous Balud Ophiolitic Complex (BOC) in the island of Masbate in the Central Philippines. Mapping of the western limb of the island revealed that only the upper crustal section of the BOC is exposed in this area. Geochemically, the pillow basalts are characterized by transitional mid-oceanic ridge basalt-island arc tholeiitic compositions. Gravity surveys yielded low Bouguer anomaly values that are consistent with the highly dismembered nature of the BOC. Short wavelength, high amplitude magnetic anomalies registered across the study area are attributed to shallow magnetic sources. This is taken to support the model that the ophiolitic complex occurs as thin crustal slivers that are not deeply-rooted in the mantle. Comparing BOC with other ophiolites in the Central Philippines, such as those in the islands of Sibuyan, Leyte and Bohol, suggests the possibility of a common or contiguous source for similarly-aged and geochemically composed crust-mantle sequences in the region.

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Section: Geophysicsmentioning

confidence: 60%

Section: Implications For Tectonic Settingsmentioning

confidence: 99%

Section: Implications For Tectonic Settingsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Geochemical and Geophysical Characteristics of the Balud Ophiolitic Complex (BOC), Masbate Island, Philippines: Implications for its Generation, Evolution and Emplacement

Manalo¹,

Dimalanta²,

Faustino-Eslava³

et al. 2015

Terr. Atmos. Ocean. Sci.

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Contrasting morphological trends of islands in Central Philippines: Speculation on their origin

Yumul¹,

Dimalanta²,

Tamayo³

et al. 2000

Island Arc

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The Palawan microcontinental block collided with the Philippine Mobile Belt in the Central Philippine region resulting in the counterclockwise rotation of MindoroMarinduque and clockwise rotation of Panay. The collision also brought about the clockwise rotation of north-east Negros, Cebu, north-west Masbate and Bohol (collectively called the Western Visayan block), resulting into their present-day northeast-southwest trend. This suggests a far more dramatic role of the collision than was previously recognized. Furthermore, the south-east Sulu Sea sub-basin is inferred to have also undergone collision-related clockwise rotation which can account for the observed east-west trending magnetic lineations in the basin. Aside from explaining the contrasting morphological trends of the different islands in Central Philippines, the rotation can also explain, albeit in a different way, how the belts of sedimentary basins, ophiolites and arcs in Panay and Negros can extend to Northern Luzon. Published paleomagnetic data suggest that the collision-related rotation commenced during the early to middle Miocene and had ceased by the late Miocene.

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Imaging crustal features and Moho depths through enhancements and inversion of gravity data from the Philippine island arc system

Casulla

Mizunaga

Tanaka

et al. 2022

Prog Earth Planet Sci

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The Philippine archipelago is a complex island arc system, where many regions still lack geopotential field studies. The high-resolution isostatic anomaly and free-air anomaly digital grids from the World Gravity Map (WGM) were processed and analyzed to present a general discussion of the Philippines’ gravity signatures and contribute to understanding its regional geology and tectonics. The isostatic anomaly map was continued upward to investigate the high-density ophiolitic basement rocks and low-gravity sedimentary basins at depth. The first vertical derivative (1VD) filter was applied to the free-air anomaly grid map to locate regional structures represented by density contrast boundaries. The depth to the top of the Moho and basement rock over the Sulu Sea was computed using the two-dimensional (2-D) radially averaged power spectrum analysis. Three-dimensional (3-D) gravity inversion was applied to some major sedimentary basins in the Philippines to present 3-D subsurface density contrast models. The interpreted gravity maps highlighted prominent geologic features (e.g., trench manifestation, ophiolite distribution, basin thickness). The negative isostatic anomalies (< 0 mGal) represent the thick sedimentary basins, while the moderate signatures (0 to 80 mGal) correspond to the metamorphic belts. The distinct very high-gravity anomalies (> 80 mGal) typify the ophiolitic basement rocks. The gravity data’s upward continuation revealed contrasting deep gravity signatures; the central Philippines with continental affinity (with 20–35 mGal) was distinguished from the regions with oceanic affinity (with 45–200 mGal). The 1VD map over the Sulu Sea showed anomalies associated with shallow features dominantly related to the Cagayan Ridge. The 2-D radially averaged power spectrum analysis exposed gravity anomalies with tectonic significance (e.g., basement characterization, Moho depth estimation). The estimated average Moho depth in the Sulu Sea is from 12 to 22 km, while the average basement depth is within the range of 5 to 11 km. Lastly, the 3-D subsurface density contrast models characterized the very low-density zones representing the deep (> 7 km) sedimentary basins in the northern Cagayan Valley and southern Central Luzon basins. Furthermore, thin (~ 3.5 km) sedimentary formations are inferred for the low-density areas in northern Agusan-Davao and eastern Cotabato basins.

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Gravity variations along the Southeast Bohol Ophiolite Complex (SEBOC), Central Philippines: Implications on Ophiolite Emplacement

Cited by 7 publications

References 14 publications

Geochemical and Geophysical Characteristics of the Balud Ophiolitic Complex (BOC), Masbate Island, Philippines: Implications for its Generation, Evolution and Emplacement

Geochemical and Geophysical Characteristics of the Balud Ophiolitic Complex (BOC), Masbate Island, Philippines: Implications for its Generation, Evolution and Emplacement

Contrasting morphological trends of islands in Central Philippines: Speculation on their origin

Imaging crustal features and Moho depths through enhancements and inversion of gravity data from the Philippine island arc system

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