scholarly journals Mineral-chemistry of silicates, Fe-Ti oxides and sulfides in gabbro and magnetitite of the Archean Nuasahi complex (India): Implications for magma fractionation, thermometry and oxygen fugacity of re-equilibration and Ni-Cu mineralization

2021 ◽  
Author(s):  
Chirasree Bhattacharjee ◽  
Sisir Mondal
Keyword(s):  
Oxygen Fugacity ◽  
Mineral Chemistry ◽  
Ti Oxides ◽  
Magma Fractionation

scholarly journals Mineralogy of an Appinitic Hornblende Gabbro and Its Significance for the Evolution of Rising Calc-Alkaline Magmas

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1088
Author(s):  
Georgia Pe-Piper
Keyword(s):  
Oxygen Fugacity ◽  
Gradual Increase ◽  
Country Rock ◽  
Ti Oxides ◽  
Hornblende Gabbro ◽  
Reducing Conditions ◽  
History Of ◽  
Alkaline Magmas ◽  
The Relationship ◽  
Hydrous Magma

The magmatic and sub-solidus evolution of calcic amphiboles and Fe–Ti oxides was investigated in the Neoproterozoic Frog Lake pluton, Nova Scotia, Canada, in order to understand the relationship between the history of hydrous magma and the resulting mineralogy. The pluton occurs as sheet-like bodies of hornblende gabbro and hornblendite, with lesser tonalite dykes and granite bodies, interlayed with screens of medium-grade metamorphic country rock. Small, diffuse clots of felsic minerals are present in the gabbro. The subsolidus growth of actinolite occurs in early clinopyroxenes and amphiboles. Ilmenite is the dominant Fe–Ti oxide, as interstitial magmatic crystals. The increase of Mn towards the margin of the ilmenite crystals indicates a gradual increase in oxygen fugacity with time, leading to the precipitation of titanite and ferrohypersthene. The replacement of titanite by ilmenite and ilmenite lamellae in the amphiboles suggests subsequent reducing conditions during the sub-solidus crystallisation. The gabbros in the coeval, but apparently shallower, Jeffers Brook granodiorite laccolith have dominant magnetite and Mg-rich subsolidus amphiboles, which are indicative of high oxygen fugacity. The differences between the two plutons suggest that there was a greater flux of hydrothermal water through the sheet-like architecture of the Frog Lake pluton.

scholarly journals MAGMA GENERATION AND MIXING IN THE EARLIEST VOLCANIC CENTRE OF SANTORINI (AKROTIRI PENINSULA). MINERAL CHEMISTRY EVIDENCE FROM THE AKROTIRI PYROCLASTICS

2017 ◽  
Vol 43 (5) ◽  
pp. 2625
Author(s):  
K. Kitsopoulos
Keyword(s):  
Magma Mixing ◽  
Mineral Chemistry ◽  
Silicic Magma ◽  
High Alumina ◽  
Primitive Mantle ◽  
Volcanic Centre ◽  
Magma Generation ◽  
High Alumina Basalt ◽  
Ti Oxides

Santorini is a dominant expression of magma generation and subsequent volcanism in the Meditereanean area, where a calk-alkaline, high-alumina, basalt-andesite-dacite type of volcanism was expressed from eight centres. The volcanics of the Akrotiri peninsula are considered to be the products of the earliest (Pliocene Pleistocene) volcanic centre. The present study has investigated the mineral chemistry of some major pyrogenic phenocrysts, such as plagioclase and Fe-Ti oxides, of the Akrotiri pyroclatics unit, which have undergone a notable zeolitization procedure. The results are compatible with magma mixing mechanism of a primitive mantle derived, saturated, of mafic composition component with silicic magma in shallow crustal depths.

Mineral chemistry and geothermometry of Fe-Ti oxides in the Khanlogh magnetite-apatite ore, northwest of Neyshabour, NE Iran

2016 ◽  
Vol 281 (3) ◽  
pp. 227-246
Author(s):  
Parvin Najafzadeh Tehrani ◽  
Ali Asghar Calagari ◽  
Francisco Velasco Roldan ◽  
Vartan Simmonds ◽  
Kamal Siahcheshm
Keyword(s):  
Mineral Chemistry ◽  
Ti Oxides ◽  
Ne Iran

Petrology of sub-cratonic pyroxenite and eclogite containing lamellae-bearing garnet, Western Gneiss Region, Norway

2020 ◽  
Author(s):  
Dirk Spengler ◽  
Taisia A. Alifirova ◽  
Herman L. M. van Roermund ◽  
Hans-Joachim Massonne
Keyword(s):  
Lithospheric Mantle ◽  
Mineral Chemistry ◽  
Wide Distribution ◽  
Stability Field ◽  
Western Gneiss Region ◽  
Entire Area ◽  
Ultra High Pressure ◽  
Ti Oxides ◽  
Lamellar Inclusions ◽  
Micron Size

<p>Garnet from the lithospheric mantle underneath cratons can contain oriented lamellar inclusions of pyroxene and oxides like rutile as a result of exsolution of majoritic and titaniferous components due to cooling and/or decreasing pressure. We investigated ten new such microstructure-bearing samples of pyroxenite and eclogite from six peridotite bodies in SW Norway, which were once located in the E Greenland mantle lithosphere. The lamellar inclusions occur in porphyroclastic garnet and vary – dependent on their size – systematically in shape, (acicular to short-prismatic), width (~50 μm to sub-micron size), spacing (several 100 to ~10 μm), and phase (pyroxene to pyroxene + Ti-oxides to Ti-oxides). Smaller lamellae can fill the space between larger lamellae, which support consecutive generations. The larger (early formed) lamellae are more poorly preserved and more difficult to locate in the suite of samples than the smaller (lately formed) exsolutes. A younger generation of lamellar and other inclusions occur lined-up along healed cracks cutting across cores but not rims of garnet. These inclusions comprise oxides, silicates, carbonates (aragonite, calcite, magnesite) and fluid inclusions (N<sub>2</sub>, CO<sub>2</sub>, H<sub>2</sub>O). Their origin either relates to the Precambrian rock history and/or to a hydrous environment as typical for mantle wedge metasomatism prior to Scandian recrystallisation. Mineral chemistry suggests that the lamellae-bearing garnet grains equilibrated at two discrete depth levels, corresponding to ~3.7 GPa (850 °C) and ~3.0 GPa (710 °C), at a cratonic geotherm corresponding to 38 mW/m<sup>2</sup> surface heat flow. Five samples contain porphyroclastic orthopyroxenes with Al<sub>2</sub>O<sub>3</sub> concentration showing W-shaped profiles and/or very low Al<sub>2</sub>O<sub>3</sub> content (0.18–0.23 wt%) in cores of large (>200 µm) recrystallised grains. Both characteristics typify short intracrystalline diffusion lengths and are consistent with an early prograde metamorphic evolution into the diamond stability field. This evolution is related to subduction during the Scandian orogeny. Porphyroclastic orthopyroxenes in other samples show U-shaped Al<sub>2</sub>O<sub>3</sub> concentration profiles and long diffusion lengths of several 100 μm, i.e. longer than the grain radius of the recrystallised grains. Their cores contain high Al<sub>2</sub>O<sub>3</sub> contents (0.65–1.16 wt%) consistent with a diffusional overprint that followed partial rock recrystallisation and obliterated pro- and peak metamorphic records. The presence of systematic exsolution microstructures in all samples demonstrates a similar early evolution of pyroxenite and eclogite in all six peridotite bodies. The wide distribution of our samples across the Western Gneiss Region indicates that (1) majoritic and titaniferous garnet occurred widespread in the E Greenland lithospheric mantle and (2) rock bodies of Scandian ultra-high pressure metamorphism can be found in nearly the entire area between Nordfjord and Storfjord and from the coast towards ~100 km in the hinterland, i.e. in a region much larger than previously anticipated.</p>

Oxygen fugacity of martian basalts from electron microprobe oxygen and TEM-EELS analyses of Fe-Ti oxides

2001 ◽  
Vol 86 (9) ◽  
pp. 1015-1024 ◽  
Author(s):  
Christopher D.K. Herd ◽  
James J. Papike ◽  
Adrian J. Brearley
Keyword(s):  
Oxygen Fugacity ◽  
Electron Microprobe ◽  
Ti Oxides
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