During the melting of a metabasaltic rock at variable depths, the Ti budget in the anatectic granitic/intermediate melt is determined by the presence of Ti bearing minerals like Titanite, rutile, ilmenite etc. in the residual and/or fractionating assemblage. How the depth of melting/pressure of melting influences the stability of these minerals?
What I know is that rutile is stable in high pressure and ilmenite in low pressure but isotherm this is a result of exhumed terrain leading to decompress or vice versa
There is a characteristic change in basic magmatic rocks. In basalts normally titaniferous magnetite, ilmenite and Ti-bearing amphibole and ulvöspinel may occur. Hydrothermal alteration products resultant from the decomposition of Fe-Ti oxides belong to the pseudobrookite or pseudorutile series under hydrothermal condition in a strongly oxidizing regime anatase (bipyramidal XX) occur, whereas in a supergene environment under near ambient conditions anatase shows up in platy XX. The end product is a mixture of Ti dioxides such as platy anattas, brookite and Fe-oxide hydrates mainly goethite. A special and rare mineral is kleberite which points to an environment of low hydrothermal conditions. Autometasomatic/ low grade metamorphic conditions are conducive to titanite, anatase in basic igneous rocks. This is also valid for low-grade to medium grade metabasic rocks where titanite is widespread and also in places the Mg-enriched modification of ilmenite. Titanite can be observed from the very-low to the medium-grade stage metamorphic rocks. A critical boundary is the transition from eclogite-amphibolite into eclogite and vice versa where rutile is common to high-T and -P metabasic rocks. Slender to acicular XX of "sagenite" forming an interwoven texture or network of rutile are common in the aftermaths of the decomposition of titaniferous biotite and hornblende when undergoing retrograde metamorphic processes and getting converted into a mash of chlorite and Ti dioxide.
You can find several papers of mine on the RG server for download.
DILL, H.G. (2007) Grain morphology of heavy minerals from marine and continental placer deposits, with special reference to Fe -Ti oxides.- Sedimentary Geology, 198: 1-27.
DILL H.G., MELCHER, F, FUESSL, M. and WEBER, B. (2007) The origin of rutile-ilmenite aggregates (“ nigrine ”) in alluvial-fluvial placers of the Hagendorf pegmatite province, NE Bavaria, Germany.- Mineralogy and Petrology, 89: 133-158.
DILL, H.G. and LUDWIG, R.-R. (2008) Geomorphological-sedimentological studies of landform types and modern placer deposits in the savanna (Southern Malawi).-Ore Geology Review , 33: 411-434.
DILL, H.G. and KLOSA, D. (2011) Heavy-mineral-based provenance analysis of Mesozoic continental-marine sediments at the western edge of the Bohemian Massif, SE Germany: With special reference to Fe-Ti minerals and the crystal morphology of heavy minerals. - International Journal of Earth Sciences, 100: 1497-1513.
DILL, H.G., GOLDMANN S., and CRAVERO, F., (2018) Zr-Ti-Fe placers along the coast of NE Argentina: Provenance analysis and ore guide for the metallogenesis in the South Atlantic Ocean. Ore Geology Reviews 95: 131-160.
HGD
Garnet The shales of Arghun Mountain have the mineral assemblages of quartz, feldspar, mica and garnet. The chemical composition of plagioclase, biotite, muscovite, chlorite and garnet shows that plagioclase is rich in albite, white mica is rich in the final members of muscovite, chlorite is more rich in the final members of amethyst and sedite, and phlogopite-anilite is basic. Garnets are rich in almandene and spesartine. In this study, the pressure and temperature of the upper limit and the lower limit of rock metamorphism were calculated using conventional geothermal-barometric methods. Using the Fe-Mg cation exchange thermometer between garnet and biotite, assuming a pressure of 4Kbar, the highest calculated temperature is 615 and the lowest calculated temperature is 429 ° C, and for 8 Kbar the highest calculated temperature is 644 and the lowest calculated temperature is 452 ° C. Using the multiple mineralogy equilibrium method, the calculated pressure and temperature for the upper and lower limits of metamorphism were about 801 ° C and 9kbar pressure, and 450 ° C and 7kbar pressure, respectively. This complex has been affected by two metamorphic and metamorphic phases of rocks. The second deformation in the region has been accompanied by the peak of metamorphism. A decrease in temperature of about 351 ° C in exchange for a decrease in pressure of about 2 kbar is observed in the metamorphic clay rocks of the study area.
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