Mineral chemistry and in situ U Pb geochronology of the mare basalt Northwest Africa 10597: Implications for low-Ti mare volcanism around 3.0 Ga

Icarus ◽  
2020 ◽  
Vol 338 ◽  
pp. 113531 ◽  
Author(s):  
Yunhua Wu ◽  
Weibiao Hsu
Keyword(s):  
Mineral Chemistry ◽  
Mare Basalt ◽  
Northwest Africa ◽  
Mare Volcanism

Mineral chemistry, P-T pseudosection and in-situ U-Th-Pbtotal monazite geochronology of Banded Iron Formation from Bundelkhand craton North-Central India, and its geodynamic significance

2021 ◽  
Author(s):  
Mohd Baqar Raza ◽  
Pritam Nasipuri ◽  
Hifzurrahman
Keyword(s):  
Central India ◽  
Mineral Chemistry ◽  
Iron Formation ◽  
Age Group ◽  
Banded Iron Formation ◽  
Tectonic Zone ◽  
Third Age ◽  
The Third ◽  
Hydrothermal Activities

<p>The Banded Iron Formation (BIF) in Bundelkhand craton (BuC) occurred as supracrustals associated with TTG’s, amphibolites, calcsilicate rocks, and quartzite within the east-west trending Bundelkhand tectonic zone (BTZ). The BIFs near Mauranipur do not show any prominent iron-rich and silica-rich layer band and are composed of garnet, amphibole, quartz, and magnetite. The volumetrically dominant monoclinic-amphiboles are grunerite in composition. X<sub>Mg</sub> of grunerite varies between 0.39-0.37. The garnets are Mn-rich, the X<sub>Spss</sub> of garnet ranges from 0.26-0.20, X<sub>Pyp</sub> and X<sub>Grs </sub>vary between 0.10-0.06 and 0.07-0.05, respectively. P-T pseudosection analysis indicates that by destabilizing iron-silicate hydroxide phases through a series of dehydration and decarbonation reactions, amphibole and garnet stabilized in BIF at temperature 400-450°C and pressure 0.1-0.2 GPa.</p><p>Massive type BIFs have monazite grains that vary from 10 to 50 µm in size, yield three distinct U-Th-Pb<sub>total</sub> age clusters. 10-20 µm sized monazite grains yield the oldest age, 3098±95 Ma. 2478±37 Ma average age is obtained from the second group, which is relatively larger and volumetrically predominant. The third age group of Monaiztes gives an age of 2088±110 Ma. ~3100 Ma monazite suggests the older supracrustal rocks of Bundelkhand craton, similar to those obtained from Singhbhum and the Dharwar craton. The 2478±37 Ma age is constrained as the timing of metamorphism and stabilization of BuC. The third age group, 2088±110 Ma probably associated with renewed hydrothermal activities, leading to rifting and emplacement of mafic dykes in BuC.</p>

Silicate and Oxide Mineral Chemistry and Textures of the Norilsk-Talnakh Ni-Cu-Platinum Group Element Ore-Bearing Intrusions

2020 ◽  
Vol 115 (6) ◽  
pp. 1227-1243 ◽  
Author(s):  
Louise Schoneveld ◽  
Stephen J. Barnes ◽  
Morgan Williams ◽  
Margaux Le Vaillant ◽  
David Paterson
Keyword(s):  
Mineral Chemistry ◽  
Relative Reduction ◽  
Phase Assemblage ◽  
Significant Drop ◽  
Liquid Component ◽  
Crystallization Sequence ◽  
History Of ◽  
Ultramafic Cumulate ◽  
Insight Into

Abstract A large proportion of the disseminated sulfide ores of the Norilsk-Talnakh camp are hosted within olivine-rich, ultramafic cumulate layers called picro-gabbrodolerite units. In this study we quantitatively analyze the chemistry and textures of the silicate and oxide minerals within olivine-bearing cumulates of the Kharaelakh, Norilsk 1, and Talnakh intrusions to determine how these intrusions compare to each other and to establish the liquidus phase assemblage and crystallization sequence and how the liquid component evolved during solidification. Crystal size distributions indicate that much of the olivine and clinopyroxene oikocrysts grew together in situ as the first of the cumulus phases at contrasting growth rates. These large clinopyroxene oikocrysts record a significant drop in Cr in the system by a significant decrease in Cr content of the outer rims compared to the cores. The chadacrysts of olivine and spinel within the clinopyroxene record the chemistry of the first stages of crystallization, while the minerals in the framework of the cumulate show a relative reduction in Cr and enrichment in incompatible elements such as Ti, Zn, Y, and the rare earth elements, indicative of the enrichment through reactions with the trapped liquid during postcumulate growth. Due to the entrapment of the olivine and spinel in rapidly growing clinopyroxene, these minerals record a history of the changing chemistry during cumulate and postcumulate growth, giving us an insight into the changing conditions during the solidification of intrusions.

In situ Pb‐Pb dating of silica‐rich Northwest Africa ( NWA ) 6594 basaltic eucrite and its constraint on thermal history of the Vestan crust

2019 ◽  
Vol 54 (12) ◽  
pp. 3064-3081 ◽  
Author(s):  
Shiyong Liao ◽  
Weibiao Hsu ◽  
Ying Wang ◽  
Ye Li ◽  
Chipui Tang ◽  
...  
Keyword(s):  
Thermal History ◽  
Northwest Africa ◽  
History Of

Glass-bearing felsic nodules from the crystallizing sidewalls of the 1944 Vesuvius magma chamber

2000 ◽  
Vol 64 (3) ◽  
pp. 481-496 ◽  
Author(s):  
P. Fulignati ◽  
P. Marianelli ◽  
A. Sbrana
Keyword(s):  
Magma Chamber ◽  
Melt Inclusions ◽  
Mineral Chemistry ◽  
Glassy Matrix ◽  
Crystal Mush ◽  
Stratigraphic Sequence ◽  
Shallow Magma Chamber ◽  
Mineral Assemblages ◽  
Pressure Crystallization

AbstractIn the 1944 Vesuvius eruption, the shallow magma chamber was disrupted during the highly energetic explosive phases. Abundant cognate xenoliths such as subvolcanic fergusites and cumulates, hornfels, skarns and rare marbles occur in tephra deposits.Mineral chemistry, melt inclusions in minerals and glassy matrix compositions show that fergusites (highly crystalline rocks made of leucite, clinopyroxene, plagioclase, olivine, apatite, oxides and glass) do not correspond to melt compositions but result from combined sidewall accumulation of crystals, formed from K-tephriphonolitic magma resident in the chamber, and in situ crystallization of the intercumulus melt. Very low H2O contents in the intercumulus glass are revealed by FTIR and apatite composition. Whole rock compositions are essentially determined by the bulk mineral assemblages.Glass–bearing fergusites constitute the outer shell of the magma chamber consisting of a highly viscous crystal mush with a melt content in the range 20–50 wt.%. The leucite/(clinopyroxene+olivine) modal ratio, varies with the extraction order of magmas from the chamber, decreasing upwards in the stratigraphic sequence. This reflects a vertical mineralogical zonation of the crystal mush. These data contribute to the interpretation of the subvolcanic low–pressure crystallization processes at the magma chamber sidewalls affecting alkaline potassic magmas.

scholarly journals Petrogenesis of lunar meteorite Northwest Africa 2977: Constraints from in situ microprobe results

2010 ◽  
Vol 45 (12) ◽  
pp. 1929-1947 ◽  
Author(s):  
Ai-Cheng ZHANG ◽  
Wei-Biao HSU ◽  
Christine FLOSS ◽  
Xian-Hua LI ◽  
Qiu-Li LI ◽  
...  
Keyword(s):  
Northwest Africa ◽  
Lunar Meteorite

New constraints on the Sulfur isotope signature of the sub-continental lithospheric mantle wedge: in situ δ34S analyses of pentlandite from the exhumed orogenic garnet-bearing peridotite of the Ulten Zone, Eastern Italian Alps

2020 ◽  
Author(s):  
Giulia Consuma ◽  
Roberto Braga ◽  
Marco L. Fiorentini ◽  
Laure Martin ◽  
Peter Tropper ◽  
...  
Keyword(s):  
Lithospheric Mantle ◽  
Mantle Wedge ◽  
Isotope Composition ◽  
Mineral Chemistry ◽  
Isotope Signature ◽  
Fine Grained ◽  
Continental Lithospheric Mantle ◽  
The Impact ◽  
S Isotope

<p>Orogenic peridotites associated with high-grade felsic rocks record mass exchange between crust and mantle reservoirs at convergent plate margins. In this geodynamic framework, fluids released by submerging slabs can mobilize redox-sensitive elements such as carbon (C) and sulfur (S) and percolate the mantle wedge, eventually forming hydrate minerals associated with carbonate and sulfide phases at appropriate T, P and f O<sub>2</sub> conditions. The introduction of sulfur into the sub-continental lithospheric mantle (SCLM) wedge and its mobilization at grain-scale can be investigated by means of in situ δ<sup>34</sup>S analyses of mantle wedge sulfides, which may have inherited the composition of the fluid sources. To date, the impact of the S transfer through the SCLM wedge is poorly known and limited in situ S isotope values of sulfides from mantle wedge peridotite are available in literature. Our study focuses on the Ulten Zone (UZ) orogenic-garnet peridotites, which provide an ideal case to investigate the S mobilization through the SCLM wedge and the effects of crustal fluids on the sulfide δ<sup>34</sup>S signature, especially during the exhumation stage. We therefore integrate a well-constrained paragenesis with mineral chemistry and in situ S isotope signature of sulfides. The UZ peridotites were involved in a collisional setting during the Variscan orogenesis, recording HP-eclogite-facies conditions and exhumation after their incorporation in a mélange with the associated garnet-kyanite gneisses. A suite of coarse to fine-grained peridotites was investigated in order to cover all the metasomatic stages preserved in these rocks, considering the grade of serpentinization and the occurrence of carbonates. Microstructural observations and major element compositions indicate that pentlandite (± chalcopyrite ± chalcocite ± sphalerite) is the ubiquitous primary sulfide, which is commonly replaced by secondary heazlewoodite and millerite in medium to highly serpentinized peridotite. Pentlandite occurs in different textural positions related to several metasomatic stages: (i) polycrystalline aggregates (pentlandite + Cl-apatite + phlogopite + ilmenite + calcite-brucite intergrowths) included in spinel (in garnet); (ii) interstitial in matrix; (iii) in carbonate and serpentine veins. Overall, the S isotope signature of pentlandite exhibits a relatively narrow range between -1.62 and +3.76 ‰. The relatively low S isotope values require a mantle-like source for the metasomatizing fluids enriched in sulfur, with possible contamination with fluids of other different sources. These new results show that sulfur was introduced into the lithospheric mantle and mobilized by influxes of late metasomatic fluids, in part related to the serpentinization, and provide additional constraints on the S isotope composition of the SCLM wedge.</p>

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