Observations of plagioclase zoning using interference imaging

Pearce, T. H.

doi:10.1016/0012-8252(90)90024-p

Cited by 69 publications

(39 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For example, slight increases in melt-H 2 O result in dissolution and crystallization of An-rich compositions (Housh and Luhr, 1991). Although normal-zoned plagioclases with small-amplitude variation are probably a result of minor local disequilibrium or small-scale pressure and temperature changes (Pearce and Kolisnik, 1990), the occurrence of disequilibrium phenocryst composition and textures such as oscillatory-zoned amphibole and plagioclase and sieved textured plagioclase cannot be explained by simple closed system fractionation alone.…”

Section: Discussionmentioning

confidence: 99%

Magma storage and plumbing of adakite-type post-ophiolite intrusions in the Sabzevar ophiolitic zone, northeast Iran

et al. 2015

View full text Add to dashboard Cite

Abstract. Subduction-related adakite-type intrusive rocks emplaced into the late Cretaceous-Paleocene Sabzevar ophiolite zone, northeast Iran, range from Mg-andesite to rhyodacite in composition. Here we investigate the magma supply system to these subvolcanic intrusive rocks by applying thermobarometric mineral and mineral-melt equilibrium models, including amphibole thermobarometry, plagioclasemelt thermobarometry and clinopyroxene-melt barometry. Based on the results of these thermobarometric models, plagioclase crystallized dominantly at pressures of ∼ 350 (130 to 468) MPa, while amphiboles record both low pressures (∼ 300 MPa) and very high pressures (> 700 MPa) of crystallization. The latter is supported by the calculated pressures for clinopyroxene crystallization (550 to 730 MPa). The association of amphibole with clinopyroxene and no plagioclase in the most primitive samples (Mg-andesites) is consistent with amphibole fractionation from very hydrous magmas at deep crustal levels of the plumbing system, which may have been a key process in intensifying adakite-type affinities in this rock suite. Barometry, combined with frequent disequilibrium features such as oscillatory-zoned and sieve-textured plagioclase crystals with An-rich overgrowths in more evolved samples, implies that final magma differentiation occurred in an open upper crustal magma system that developed progressively stronger compositional modifications during high-level magma storage.

show abstract

Section: Discussionmentioning

confidence: 99%

Magma storage and plumbing of adakite-type post-ophiolite intrusions in the Sabzevar ophiolitic zone, northeast Iran

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Resorption in plagioclase could result in dissolution surfaces and could happen due to rapid growth. Decompression can produce pervasive resorption as well (Pearce & Kolisnik, 1990).…”

Section: Bombsmentioning

confidence: 99%

Petrographic Analysis of the Volcanic Bombs and Blocks from Poás Volcano: April-June 2017 Eruptive Period

Madrigal¹,

Lücke²

2017

Rev. Geol. Amér. Central

View full text Add to dashboard Cite

During the first semester of 2017, Poás Volcano, in the Central American Volcanic Arc (CAVA) initiated a period of volcanic unrest that included high energy phreatomagmatic and magmatic eruptions. The most notable eruptions occurred on April 14 th and April 22 nd of 2017, which produced abundant ashes and ballistic materials in the form of blocks and bombs. Here, we present results from the petrographic analyses conducted in the collected material from the largest eruptions of April 2017. Mineral textures observed on the petrographic analyses show evidence of reactivation and fragmentation of a crystal mush in the magma chamber, triggering re-melting episodes, volatile exsolution, and an increase in the pressure of the system, all of which are expected conditions during an eruption episode. Our analyses done on juvenile and non-juvenile material suggest that processes of magma mingling and injections of new batches of material of different compositions have played an important role throughout previous eruptions and likely in the current phase of volcanic activity in Poás.

show abstract

“…Ginibre et al [17] review the techniques for the characterization of compositional zoning and their associated uncertainties. Pearce and Kolisnik [43] review the criteria for crystals that will be optimal for zoning study. They should be euhedral, nearly center-cut, and with zoning nearly perpendicular to the plane of the thin section.…”

Section: Step One: Data Acquisitionmentioning

confidence: 99%