Refractory- and metallurgical-type chromite ores, Zambales ophiolite, Luzon, Philippines

Hock, M.; Friedrich, G.; Plüger, W. L.; Wichowski, A.

doi:10.1007/bf00199799

Cited by 25 publications

(10 citation statements)

References 15 publications

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“…Previous works have also highlighted the prevalence of podiform chromitites within the mantle peridotites of the ZOC. More specifically, it has been reported that Cr-rich podiform chromitites can be found in the Acoje block whereas Al-rich podiform chromitites are present in the Coto Block (Stoll, 1958;Hock et al, 1986). This bimodal occurrence has been attributed to differing conditions in terms of multi-stage melting, high water pressure and oxygen fugacity during the formation of the two blocks.…”

Section: Geological Settingmentioning

confidence: 99%

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Textural Evidence for the Chromite‐Oversaturated Character of the Melt Involved in Podiform Chromitite Formation

et al. 2013

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Well-preserved oval-shaped dunite clots occur within the exceptionally fresh massive podiform chromitites from the Coto Block of the Zambales Ophiolite Complex, the Philippines. The dunite/ chromitite boundary shows an interlocking texture; olivine inclusions in chromites in the podiform chromitites show the same optical extinction with larger adjacent olivines in the dunite clots. This texture was formed by the reaction between chromite-oversaturated melt and its dunite inclusions. The existence of such type of melt was previously only hypothesized to explain the origin of layered and podiform chromitites but is now confirmed by this discovery.

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Section: Geological Settingmentioning

confidence: 99%

“…The location of the Acoje and Coto blocks within the Masinloc massif is indicated by the stars. present in the Coto Block (Stoll, 1958;Hock et al, 1986). This bimodal occurrence has been attributed to differing conditions in terms of multi-stage melting, high water pressure and oxygen fugacity during the formation of the two blocks.…”

Section: Geological Settingmentioning

confidence: 99%

Textural Evidence for the Chromite‐Oversaturated Character of the Melt Involved in Podiform Chromitite Formation

et al. 2013

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“…These carbonate mineral groups are common impurities of chromite ore, the major local source of the Zambales ophiolite. 37 , 38 The upsurge in K at Station 4 (0.821–2.01 mg/g), on the other hand, could be a result of runoff from rice farms that bound the floodplains at the mid- and downstream stations. The rice farming communities in the area highly depend on synthetic, inorganic fertilizers to improve their crop harvests.…”

Section: Discussionmentioning

confidence: 99%

Metal Concentrations in Sediments of the Alinsaog River, Santa Cruz, Zambales, Central Luzon, Philippines

Sazon

Migo

2020

Journal of Health and Pollution

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Background. Efforts are needed to evaluate heavy metal concentrations in aquatic sediments which serve as repositories and as sources of contamination of other habitats. Objectives. The present study assessed temporal changes in the pH, particle size and concentration of metals in sediments of a mining-affected river in Zambales, Philippines. Methods. Sediment samples were collected at different periods in four stations along the river using a modified Van Veen grab. The samples were subjected to quartering, air-drying, and sieved through a mesh of 40 mm prior to X-ray fluorescence spectroscopy analysis using Thermo Scientific Niton XL3t to determine metal concentrations. The sediment particle size was analyzed by the sieve method and soil pH by the electrode method. Results. Measured metal concentrations in the sediment were as follows: iron (Fe)> calcium (Ca)> chromium (Cr)> nickel (Ni)> manganese (Mn) with averages of 174.6 mg/g, 7.89 mg/g, 6.54 mg/g, 4.82 mg/g, and 2.75 mg/g dry matter (DM), respectively. The mean pH of riverine sediments was generally neutral, except for Station 4. In terms of particle size, silt and clay fractions increased in the upstream station but decreased in the midstream and downstream stations across the sampling periods. The flooding brought by Typhoon Koppu resulted in lowered concentrations of Fe, Mn, Cr, and Ni and an upsurge in Ca and potassium levels. Discussion. Most of the heavy metals (Fe, Ni, Cr, Mn) exceeded the probable effect level (PEL) for inorganics in sediments, suggesting that the adverse effects of these metals on the environment and aquatic organisms are expected to occur frequently. In comparison with Station 4, which was less affected by siltation, there was a sign of metal enrichment in the area. This indicates that soil erosion and runoff, which might have been triggered by vegetation loss, mineral extraction, and agricultural activities, had a significant impact on the quality of river sediments. Conclusions. The findings of the study point to the need for the formulation and implementation of appropriate regulatory measures for the protection and rehabilitation of the heavy metal-loaded river. Competing Interests. The authors declare no competing financial interests.

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“…Through a combination of these reactions and fractional crystallization, the melt will become saturated to supersaturated, first with respect to chromian spinel and olivine and then with respect to pyroxene. This step is seen clearly in cogenetic dikes in the mantle sections of the Oman (Ceuleneer and Nicolas, 1985), Zambales (Hock et al, 1986), and Bay of Islands (Edwards, 1990(Edwards, , 1995 ophiolites, where pyroxenite dikes formed after pods of chromitite and dikes of chromian spinel-bearing dunite.…”

Section: Melt and Peridotite Reaction And Crystallization Of Chromianmentioning

confidence: 94%

New insights concerning the influence of water during the formation of podiform chromitite

Edwards¹,

Pearce²,

Freeman³

2000

Ophiolites and Oceanic Crust: New Insights From Field Studies and the Ocean Drilling Program

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Podiform chromitites are pod-like bodies dominated by chromian spinel and enveloped by dunite. Most major bodies are Cr rich and occur in the harzburgitic mantle section and the mantle-crust transition zone of ophiolites formed in suprasubduction zone environments. Current models for the origin of podiform chromitites require a combination of crystal fractionation and melt-peridotite reaction as basaltic melt migrates through the upper mantle. Although such models in general account for large accumulations of chromian spinel and the field and textural relationships in and around podiform bodies, they do not adequately deal with the problem of the low solubility of Cr in basaltic melts, which begs the questions: How does Cr enter melt and why is it transported to a restricted zone in a melt conduit where accumulation of chromian spinel takes place? The present study suggests that the answer may lie with water and its ability to depolymerize the silica network of the melt. The formation of most, if not all, melts capable of forming podiform chromitites requires the involvement of water in the zone of melt generation. Water not only promotes partial melting of refractory peridotites, it also dissolves in the resulting melt. This hydrous melt will have a greater abundance of octahedral sites than its anhydrous equivalent, and this modification promotes greater solubility of Cr in the hydrous melt owing to the high octahedral site preference energy of Cr 3ϩ -the major ion controlling Cr solubility. Cr is held in the melt until the melt and peridotite reaction raises the Si content and extent of polymerization of the melt (so that the concentration of octahedral sites is reduced), at which point the Cr becomes insoluble and chromian spinel precipitates. Growth of chromian spinel takes place in an open system in which there is a continuous supply of Cr-rich melt during a melting episode. An examination of the partial-melting history of peridotites preserved in the Troodos ophiolite, Cyprus, indicates that Cr behaves as an incompatible element during the hydrous melting of refractory peridotites. The highest Cr contents of melts that separate from these peridotites are rarely seen in the extrusive sequences of the Troodos ophiolite, suggesting that these melts fractionated substantial volumes of chromian spinel prior to eruption.

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Refractory- and metallurgical-type chromite ores, Zambales ophiolite, Luzon, Philippines

Cited by 25 publications

References 15 publications

Textural Evidence for the Chromite‐Oversaturated Character of the Melt Involved in Podiform Chromitite Formation

Textural Evidence for the Chromite‐Oversaturated Character of the Melt Involved in Podiform Chromitite Formation

Metal Concentrations in Sediments of the Alinsaog River, Santa Cruz, Zambales, Central Luzon, Philippines

New insights concerning the influence of water during the formation of podiform chromitite

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