Low‐temperature hydrogen formation during aqueous alteration of serpentinized peridotite in the Samail ophiolite

2021 ◽  
Author(s):  
Eric T. Ellison ◽  
Alexis S. Templeton ◽  
Spencer D. Zeigler ◽  
Lisa E. Mayhew ◽  
Peter B. Kelemen ◽  
...  
Keyword(s):  
Low Temperature ◽  
Hydrogen Formation ◽  
Aqueous Alteration ◽  
Serpentinized Peridotite

scholarly journals Low temperature aqueous alteration of basalt: Mineral assemblages of Deccan basalts and implications for Mars

2012 ◽  
Vol 117 (E11) ◽  
pp. n/a-n/a ◽  
Author(s):  
R. N. Greenberger ◽  
J. F. Mustard ◽  
P. S. Kumar ◽  
M. D. Dyar ◽  
E. A. Breves ◽  
...  
Keyword(s):  
Low Temperature ◽  
Aqueous Alteration ◽  
Mineral Assemblages

Crustal geochemistry in the Wawa–Foleyet region, Ontario

1994 ◽  
Vol 31 (7) ◽  
pp. 1104-1121 ◽  
Author(s):  
D. M. Shaw ◽  
A. P. Dickin ◽  
H. Li ◽  
R. H. McNutt ◽  
H. P. Schwarcz ◽  
...  
Keyword(s):  
Low Temperature ◽  
Continental Crust ◽  
Major Elements ◽  
Chemical Compositions ◽  
Transition Elements ◽  
Aqueous Alteration ◽  
Clastic Sediments ◽  
Greenstone Belts ◽  
Regional Abundance ◽  
Fluid Homogenization

Fifty-three rock samples from the Kapuskasing structural zone (KSZ) and 56 from the Wawa domal gneiss terrane (WGT), Ontario, have been analysed for major elements, 32 trace elements, and δ18O; δD was measured in a few samples.Average chemical compositions for the KSZ and WGT regions have been calculated from map unit averages weighted by regional abundance. Compared with estimates of the composition of the upper continental crust (UCC), the KSZ is enriched in Al, Fe, Mg, Ca, P, transition elements, Sc, and Sr; depleted in Si, B, most rare earth elements, Zr, Hf, Nb, Ta, Li, Na, K, U, Th, Ba, and Rb; but similar in composition to estimates of the lower continental crust. The WGT is closer in composition to the UCC. These data support the interpretation, on geophysical and petrological grounds, that the crust here is layered and has been uplifted, the WGT and KSZ regions representing progressively deeper levels.Igneous rock and orthogneiss δ18O values in the KSZ and WGT show good correlation with the weight percentages of SiO2. Paragneisses and clastic sediments and metavolcanics in the Michipicoten greenstone belt have higher ratios, as in other greenstone belts. Low δ18O and high δD values in most of the higher grade mafic gneisses show that they have never undergone low-temperature marine alteration. However, a few mafic gneisses with relict pillows show δ18O and δD values indicating low-temperature aqueous alteration. The δ18O and δD evidence throughout the two regions supports the view that no regional fluid homogenization took place.Errorchron ages of 2725 ± 130 Ma (Rb/Sr) and 2755 ± 110 Ma (Sm/Nd) were obtained for tonalite–granodiorite gneiss and agree within error with results from other workers. The intrusive Floranna Lake complex is 2580 ± 120 Ma (Rb/Sr), not significantly different from the age of the tonalite. Scatter in the data is to be attributed to localized late-stage alteration under low water–rock ratios by Sr-rich–Rb-poor brines. Model Nd ages suggest that there is no old crust [Formula: see text] in the region and that the 2700 Ma mantle was depleted relative to the bulk earth.

scholarly journals Exogenous copper sulfide in returned asteroid Itokawa regolith grains are likely relicts of prior impacting body

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Katherine D. Burgess ◽  
Rhonda M. Stroud
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Low Temperature ◽  
Copper Sulfide ◽  
Parent Body ◽  
Carbonaceous Chondrites ◽  
Aqueous Alteration ◽  
Thermal Alteration ◽  
Transmission Electron ◽  
Rubble Pile

AbstractSamples from asteroid 25143 Itokawa returned by the Hayabusa mission have been identified as LL4-6 ordinary chondrite materials and have shown it to be a rubble pile that aggregated after break-up of a parent body. Here we investigate particle RB-CV-0038 from the Itokawa regolith using scanning and transmission electron microscopy and energy dispersive spectroscopy. We identify a cubanite-chalcopyrite-troilite-pyrrhotite assemblage, the phases and structure of which are indicative of low-temperature, aqueous alteration. Cubanite is stable only at temperatures below around 250 °C and has thus far only been identified in CI carbonaceous chondrites and the comet 81P/Wild2 sample suite. Chalcopyrite is also very rare in the meteorite record and is found mostly in R chondrites and some CK chondrites. Because the Itokawa parent body experienced significant thermal alteration with little evidence of low-temperature equilibration or aqueous alteration, we propose that the assemblage we identify is most likely exogenous and represents a component of an impacting body.

Mise en place et pétrologie du granite associé au complexe ophiolitique de Thetford Mines, Québec

1984 ◽  
Vol 21 (10) ◽  
pp. 1114-1125 ◽  
Author(s):  
Roger Laurent ◽  
Mehmet F. Taner ◽  
Jean Bertrand
Keyword(s):  
Low Temperature ◽  
Mineral Assemblage ◽  
Shear Zones ◽  
Low Pressure ◽  
Late Ordovician ◽  
Calc Alkaline ◽  
Ophiolite Complex ◽  
Serpentinized Peridotite ◽  
Thrust Plane

Sheets of granite are confined to shear zones in the tectonite peridotite unit of the Thetford Mines ophiolite complex. Their orientation is parallel to the thrust plane at the base of the complex. The granite, which is calc-alkaline and rich in potassium, does not belong to the ophiolite sequence. We show that it was tectonically incorporated within the partially serpentinized peridotite during thrusting and emplacement of the complex.During this process, the granite was strongly deformed and recrystallized at low pressure (500 bar (50 MPa)) and low temperature (500 °C or less), which gave rise to the mineral assemblage orthoclase, albite, hydromuscovite, and hydrothermal biotite. This episode was followed by a rodingite alteration, characterized by the formation of grossular, which was associated with the development of economic chrysotile within the enclosing peridotite. The K–Ar ages of biotite, muscovite, and feldspar from the granite cluster around 450 Ma. These cooling ages suggest that the emplacement and alteration of the granite and peridotite had ended by Late Ordovician time.

scholarly journals Low-temperature aqueous alteration on the CR chondrite parent body: Implications from in situ oxygen-isotope analyses

2018 ◽  
Vol 222 ◽  
pp. 230-252 ◽  
Author(s):  
Christine E. Jilly-Rehak ◽  
Gary R. Huss ◽  
Kazu Nagashima ◽  
Devin L. Schrader
Keyword(s):  
Low Temperature ◽  
Oxygen Isotope ◽  
Parent Body ◽  
Aqueous Alteration ◽  
Isotope Analyses

Exsolution and inversion in pigeonite from the Whin Sill, Northern England

1978 ◽  
Vol 36 (1) ◽  
pp. 474-475
Author(s):  
P.P.K. Smith
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Homogeneous Nucleation ◽  
Silicate Mineral ◽  
Antiphase Boundaries ◽  
Two Phase ◽  
Primitive Form ◽  
The Core ◽  
Nucleation Mechanisms ◽  
And Inversion

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.

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