Phase and structural transformations of feldspars under hydrothermal conditions

Journal Article · Thu Dec 01 04:00:00 EST 1977 · Int. Geol. Rev.; (United States)

DOI:https://doi.org/10.1080/00206817709471145· OSTI ID:6807883

Kotov, N V; Ryumin, A A; Frank-Kamenetskiy, V A

Hydrothermal treatment of albite, labradorite, and orthoclase in mixtures with dolomite revealed that at P/sub H/sub 2/O/ = 1000 kg/cm/sup 2/ and a residence time of 24 to 72 hr at T = 200 to 400/sup 0/C, mainly calcite and trioctahedral layered silicates are formed. At 300 to 500/sup 0/ the following formation sequence was observed: montmorillonite ..-->.. (Mg, Al) serpentine ..-->.. chlorite from plagioclases and montmorillonite ..-->.. a disordered mixed-layer phase of the mica-montmorillonite type ..-->.. phlogopite from orthoclase. At 500 to 600/sup 0/ there is a tendency for formation of framework aluminosilicates (nepheline, kalsilite) at high Na and K concentrations in the initial mixtures, and nesosilicates (monticellite, forsterite) at high Ca and Mg concentrations. It is shown that as the residence time is increased synthetic and natural montmorillonites with Al/sup IV/ are not converted to ordered 1:1 mixed-layer phases, in contrast to those observed in systems with kaolinite. This is probably due to the statistically uniform distribution of Al in a structure of beidellite-type montmorillonites synthesized from feldspars, whereas beidellites with polar distribution of Al/sup IV/ over the (Si, Al-O) tetrahedral networks are apparently developed from kaolinite. When the albite structure is converted to the pyroxene structure, a considerable part of the tetrahedra is inherited by the latter; this follows from retention of the values of the chemical shift and quadrupole splitting typical of tetrahedral /sup 57/Fe(III). The experimental data can be used to reconstruct the primary mineral composition of metamorphic pararocks.

• OSTI ID: 6807883
• Journal Information: Int. Geol. Rev.; (United States), Journal Name: Int. Geol. Rev.; (United States) Vol. 19:12; ISSN IGREA
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152003* -- Geothermal Data & Theory-- Rock-Water-Gas Interactions
ALBITE
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
ANORTHOSITES
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE ROCKS
CARBONATES
CHEMICAL COMPOSITION
DISPERSIONS
DOLOMITE
FELDSPARS
HIGH TEMPERATURE
HYDROTHERMAL ALTERATION
HYDROTHERMAL SYNTHESIS
IGNEOUS ROCKS
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MINERALS
MIXTURES
OXYGEN COMPOUNDS
PHASE STUDIES
PYROXENES
RESERVOIR ROCK
ROCK-FLUID INTERACTIONS
ROCKS
SILICATES
SILICON COMPOUNDS
SYNTHESIS