Garnet-orthopyroxene and orthopyroxene-clinopyroxene relationships in simple and complex systems

Wood, Bernard J.; Banno, Shohei

doi:10.1007/bf00371501

Cited by 1,026 publications

(352 citation statements)

References 16 publications

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“…The coexistence of different kinds of pyroxenes in Units 84, 87, and 52 enables the use of the pyroxene thermometers. The augitepigeonite association gives equilibrium temperatures in the range 1050°−1000°C for the aphyric olivine basalt (Unit 84), and 1000°− 950°C for the more evolved aphyric basalt (Unit 52), using the method of Wood and Banno (1973). Temperatures for the orthopyroxeneaugite association present in Unit 87 are slightly lower (around 940°C).…”

Section: Pyroxenesmentioning

confidence: 99%

Mineral chemistry of volcanic sequences from Hole 917A, southeast Greenland Margin

Demant¹

1998

Proceedings of the Ocean Drilling Program

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During Ocean Drilling Program Leg 152, a 779-m-thick volcanic sequence was drilled at Hole 917A, on the feather edge of the seaward-dipping reflector sequence. The volcanic succession, which erupted under subaerial conditions, was subdivided into three series (Upper, Middle, and Lower) and 92 flow units. The Upper Series comprises picrites and olivine-phyric basalts. The Middle Series basalts are more evolved, and dacitic lavas and tuffs were erupted at the base of this series. Lavas from the Lower Series show a wider compositional range. A detailed mineralogical study of the different petrographical types shows that olivine is the principal phenocryst phase in the basalts, whereas clinopyroxene and plagioclase are the main components of the groundmass. High-Mg olivines (up to Fo 92.4 ) with chrome-spinel inclusions are abundant in the picrites and olivine-phyric basalts. Fo-content of the olivine decreases as a function of the composition of the whole rock except in some aphyric basalts with ophitic textures where the olivine underwent further re-equilibration during cooling. Plagioclase exhibits a large compositional range from bytownite (An 91 ) in the more primitive basalts to oligoclase (An 21 ) for the late crystallizing feldspar in the ophitic textures. Plagioclases from the Upper Series lavas are very poor in K 2 O. The presence of bytownite phenocrysts (An 86− 66 ) associated with sodic sieve-textured plagioclase (An 36−26 ) in the dacite (Unit 54) clearly demonstrates that this lava is a mixed lava. Pyroxenes are mainly clinopyroxene, but pigeonite and orthopyroxene were found in the matrix of some differentiated basalts with ophitic textures. The low Ti contents of the pyroxenes and the evolution trends are typical of tholeiitic lavas. The development of sector zoning in pyroxene microphenocrysts of the more differentiated basalts has a scattering effect on the distribution of the points on the pyroxene quadrilateral. Opaque oxides crystallize late and are mainly titanomagnetite. Ilmenite is also present in some lavas.The volcanic succession drilled at Hole 917A presents many petrographical and mineralogical similarities to the flood basalts of the Scoresby Sund region in East Greenland. These thick basaltic sequences, which characterize the North Atlantic volcanic rifted margins, were emplaced during a short time interval during the phase of continental breakup. The Lower and Middle Series have evolved in crustal magma chambers. The frequency of picrites in the Upper Series emphasizes an easier access of more primitive magmas to the surface during the final phase of rifting.

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Section: Pyroxenesmentioning

confidence: 99%

Mineral chemistry of volcanic sequences from Hole 917A, southeast Greenland Margin

Demant¹

1998

Proceedings of the Ocean Drilling Program

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“…The methods of Wood and Banno (1973), Mysen (1976), and Mori (1977 gave a temperature in the range 1000-1130~ whereas that of Wells (1977) gave 900~ According to Donaldson (1978) part of this difference in temperature may be due to the large errors in estimating the A1 w contents of the pyroxene. Bearing in mind the views of Nielson-Pike (1976) that the complexity of natural systems renders difficult any comparison with simplified model systems, one may state cautiously that the Bayuda spinellherzolite inclusions indicate a probable source temperature in the range 900-1130 ~ Conclusions.…”

Section: Mineralogy Of the Inclusionsmentioning

confidence: 97%

Spinel-lherzolite inclusions in basaltic rocks from Bayuda, Sudan

Hamad

1982

Mineral. mag.

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“…Applying the equations of Wood and Banno (1973) and Maxey and Vogel (1974) to calculate reequilibrium temperatures, strong variations in the Kd values (distribuition coefficient for coexisting OPX and CPX) were obtained. The Kd values calculated for the Várzea Alegre samples ranging from 0.44 to 0.66 are compatible to metamorphic processes.…”

Section: Geothermometry and Geobarometrymentioning

confidence: 99%

Evidence of mingling between contrasting magmas in a deep plutonic environment: the example of Várzea Alegre, in the Ribeira Mobile Belt, Espírito Santo, Brazil

Medeiros¹,

WIEDEMANN-LEONARDOS

Vriend³

2001

An. Acad. Bras. Ciênc.

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At the end of the geotectonic cycle that shaped the northern segment of the Ribeira Mobile Belt (Upper Proterozoic to Paleozoic age), a late to post-collisional set of plutonic complexes, consisting of a wide range of lithotypes, intruded all metamorphic units. The Várzea Alegre Intrusive Complex is a post-collisional complex. The younger intrusion consists of an inversely zoned multistage structure envolved by a large early emplaced ring of megaporphyritic charnoenderbitic rocks. The combination of field, petrographic and geochemical data reveals the presence of at least two different series of igneous rocks. The first originated from the partial melting of the mantle. This was previously enriched in incompatible elements, low and intermediate REE and some HFS-elements. A second enrichment in LREE and incompatible elements in this series was due to the mingling with a crustal granitic magma. This mingling process changed the composition of the original tholeiitic magma towards a medium-K calc-alkalic magma to produce a suite of basic to intermediate rock types. The granitic magma from the second high-K, calc-alkalic suite originated from the partial melting of the continental crust, but with strong influence of mantle-derived melts.

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Garnet-orthopyroxene and orthopyroxene-clinopyroxene relationships in simple and complex systems

Cited by 1,026 publications

References 16 publications

Mineral chemistry of volcanic sequences from Hole 917A, southeast Greenland Margin

Mineral chemistry of volcanic sequences from Hole 917A, southeast Greenland Margin

Spinel-lherzolite inclusions in basaltic rocks from Bayuda, Sudan

Evidence of mingling between contrasting magmas in a deep plutonic environment: the example of Várzea Alegre, in the Ribeira Mobile Belt, Espírito Santo, Brazil

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