Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Graphical analysis of the orthopyroxene-pigeonite-augite-plagioclase equilibrium at liquidus temperatures and low pressure

Rais M. Latypov, Michail I. Dubrovskii and Tuomo T. Alapieti
Graphical analysis of the orthopyroxene-pigeonite-augite-plagioclase equilibrium at liquidus temperatures and low pressure
American Mineralogist (April 2001) 86 (4): 547-554

Abstract

There are both natural and experimental observations of the coexistence of three pyroxenes-orthopyroxene (Opx)+pigeonite (Pig)+augite (Aug) -- with plagioclase (Pl). Commonly, the assemblage occurs as an intermediate product in the following fractionation trend of a mafic magma: Opx+Aug+Pl-->Opx+Aug+Pig+Pl-->Aug+Pig+Pl. To clarify the phase-equilibria constraints on the existence of this mineral assemblage, we have graphically analyzed the change in topology of an isobaric-isoplethic section, Ol-Aug-Pl-Qtz [with fe = 25-50%, where fe = Fe/(Fe+Mg), and An = 50%], arising from an increase in the fe-value of silicate liquid. The analysis shows that the stability field of the mineral assemblage Opx+Aug+Pig+Pl is restricted, and can only crystallize in the interval between two invariant points -- T (super 4) (sub 1) (Ol+Opx+Pig+Aug+Pl+L) and T (super 4) (sub 2) (Qtz+Opx+Pig+Aug+Pl+L) -- that emerge successively during expansion of a liquidus volume of pigeonite within the isobaric-isoplethic section Ol-Aug-Pl-Qtz. At fe-values lower than T (super 4) (sub 1) , the 3-pyroxene assemblage cannot exist due to the absence of a contact surface between the primary volumes of plagioclase and pigeonite. At fe-values greater than T (super 4) (sub 2) , the assemblage is unstable due to separation of the primary volumes of orthopyroxene and augite.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 86
Serial Issue: 4
Title: Graphical analysis of the orthopyroxene-pigeonite-augite-plagioclase equilibrium at liquidus temperatures and low pressure
Affiliation: Kola Science Center, Geological Institute, Apatity, Russian Federation
Pages: 547-554
Published: 200104
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 22
Accession Number: 2001-049396
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Secondary Affiliation: University of Oulu, FIN, Finland
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200115
Close Modal

or Create an Account

Close Modal
Close Modal