GEOLOGICAL SOCIETY OF THE PHILIPPINES

Chromite Chemistry: Implications to its Genesis and

the Environment of Formation

 

1R.A.Santos, 2 K. Suzuki, 1B. Takano, 2Y.Tatsumi, 3Y.Miyata, and 3Y. Nozaki

1Dept. of Systems Sciences, University of Tokyo and Mines and Geosciences Bureau, Philippines,

2Institute for Geothermal Sciences, Kyoto University. 3 Ocean Research Institute, University of Tokyo

 

Chromitite formation in ophiolite complexes has been a topic of debate in the field of petrochemistry. Earlier concepts considered multiple stage-partial melting and magma mixing as the main processes for its formation. With the advent of the melt-rock interaction theory, controversies on the unity of the Cr# (Cr/ Cr + Al + Fe) and Mg# (Mg/ Fe + Mg) of both the dunite rind and the enclosing harzburgite, the presence of dunitic envelope in both the Al-rich and Cr-rich chromitites, and the relative abundance of incompatible elements such as Ti and REEs in chromitites compared to the peridotite host have been resolved. Recent studies on the Re-Os isotopic signature of chromitites and of the peridotite (the dunite envelope and the adjacent harzburgite) hosts from two ophiolite complexes, the Palawan (POC) and the Dinagat ophiolite (DOC)complexes, yielded results which are suggestive of multiple processes in chromitite formation even within an ophiolite body. Chromitite formation within a single ophiolitic complex may not even be core view. 

 
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