Potential origin of the potassium depth relationship in the Bataan Orogene, the Philippines

Thesis/Dissertation · Tue Jan 01 00:00:00 EST 1985

OSTI ID:5175940

Defant, M J

Three classic volcanic arcs have developed in western Luzon, the Philippines as a result of subduction associated with an eastward-dipping Benioff zone. A data set for about 200 samples was determined for this end which includes: (1) major and various trace elements, (2) 30 initial /sup 87/Sr//sup 86/SR (0.7038 to 0.7054) and a few /sup 143/Nd//sup 144/Nd ratios (0.512921 to 0.512999), (3) 76 conventional K/Ar radiometric dates, and (4) in addition to standard model mineral analyses, over 600 microprobe analyses of 33 thin-sections. Based on these data, several conclusions can be made. (1) Excellent linear correlations exist between SiO/sub 2/ and the incompatible elements. Moreover, normalized potassium concentration increase with assumed depth to the subducting slab and away from the Manila Trench. (2) Incompatible elements do not appear to have been affected by alteration or weathering. (3) Assimilation and contamination have played an insignificant role in affecting original magma compositions. (4) Derivation of the Bataan volcanic rocks by different degrees of partial melting of the mantle can be ruled out. The mantle sources become increasingly more enriched in incompatible elements and radiogenic strontium away from the Manila Trench. (5) All three arcs have undergone early non-selective crystal fractionation of plagioclase, clinopyroxene, magnetitite, and/or olivine based on mass-balance calculations. (6) Parallel trends noted in both whole-rock and groundmass Harker diagrams (except the potassium Harker diagrams) among the arcs are probably the result of crystal fractionation. The variations in slopes observed in potassium Harker diagrams between the arcs can be explained by a combination of original primary magma potassium variations between the arcs and the fractionation of similar phases within each arc.

• Research Organization: Florida State Univ., Tallahassee (USA)
• OSTI ID: 5175940
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
GEOLOGIC DEPOSITS
GEOCHEMISTRY
PHILIPPINES
POTASSIUM
DISTRIBUTION
ARGON
CHEMICAL ANALYSIS
CORRELATIONS
DEPTH
GEOLOGIC HISTORY
ISOTOPE RATIO
ORIGIN
STRONTIUM
VOLCANIC ROCKS
ALKALI METALS
ALKALINE EARTH METALS
ASIA
CHEMISTRY
DEVELOPING COUNTRIES
DIMENSIONS
ELEMENTS
FLUIDS
GASES
IGNEOUS ROCKS
ISLANDS
METALS
NONMETALS
RARE GASES
ROCKS
580400* - Geochemistry- (-1989)