A procedure for calculating the equilibrium distribution of trace elements among the minerals of cumulate rocks, and the concentration of trace elements in the coexisting liquids

Bédard, Jean H.

doi:10.1016/0009-2541(94)90173-2

Cited by 259 publications

(115 citation statements)

References 40 publications

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“…Similar chemical effects are documented in cumulates (Bédard 1994;Coogan et al 2000;Charlier et al 2005;Gao et al 2007; and are largely caused by in situ fractional crystallization of trapped melts (see the next paragraph). These studies have pointed out that, in cumulate rocks, only the cores of large cumulus crystals can be considered reliable to infer the compositions of equilibrium melts, because they are most likely unaffected by the trapped melts.…”

Section: Composition Of Impregnating Meltssupporting

confidence: 65%

“…By contrast, in the Mt.Maggiore peridotites preserved within-mineral chemical zoning and the striking correlation between chemical variations in clinopyroxene and its textural occurrence make a strong case that trace element enrichment at rims of reacted clinopyroxene porphyroclasts and in interstitial cpx grains within the gabbronoritic veinlets, was related to in situ melt-rock interaction and crystallization of trapped melts. This inference is based on the evidence that similar compositional variations are frequently observed in minerals from cumulate rocks (Bédard 1994;Charlier et al 2005;Coogan et al 2000;Gao et al 2007; and have been ascribed to in situ crystallization and interaction between cumulus minerals and interstitial melts.…”

Section: Chemical Changes In Minerals: Evidence Of Trapped Melt Crystmentioning

confidence: 94%

“…An estimate of the amount of trapped melt (trapped melt fraction TMF) crystallized within a mineral matrix can be obtained using the Equilibrium Distribution Method (EDM) proposed by Bédard (1994). This mass balance model is based on the bulk rock trace element and modal compositions, and assumes that the trapped melt fraction is a phase crystallizing with solid/liquid D = 1.…”

Section: Chemical Changes In Minerals: Evidence Of Trapped Melt Crystmentioning

confidence: 99%

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Multi-stage melt–rock interaction in the Mt. Maggiore (Corsica, France) ophiolitic peridotites: microstructural and geochemical evidence

Rampone

Piccardo

Hofmann

2008

Contrib Mineral Petrol

110

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Spinel and plagioclase peridotites from the Mt.Maggiore (Corsica, France) ophiolitic massif record a composite asthenosphere-lithosphere history of partial melting and subsequent multi-stage melt-rock interaction. Cpx-poor spinel lherzolites are consistent with mantle residues after low-degree fractional melting (F = 5-10%). Opx + spinel symplectites at the rims of orthopyroxene porphyroclasts indicate post-melting lithospheric cooling (T = 970-1,100°C); this was followed by formation of olivine embayments within pyroxene porphyroclasts by melt-rock interaction. Enrichment in modal olivine (up to 85 wt%) at constant bulk Mg values, and variable absolute REE contents (at constant LREE/HREE) indicate olivine precipitation and pyroxene dissolution during reactive porous melt flow. This stage occurred at spinel-facies depths, after incorporation of the peridotites in the thermal lithosphere. Plagioclase-enriched peridotites show melt impregnation microtextures, like opx + plag intergrowths replacing exsolved cpx porphyroclasts and interstitial gabbronoritic veinlets. This second melt-rock interaction stage caused systematic chemical changes in clinopyroxene (e.g. Ti, REE, Zr, Y increase), related to the concomitant effects of local melt-rock interaction at decreasing melt mass, and crystallization of small (\3%) trapped melt fractions. LREE depletion in minerals of the gabbronoritic veinlets indicates that the impregnating melts were more depleted than normal MORB. Preserved microtextural evidence of previous melt-rock interaction in the impregnated peridotites suggests that they were progressively uplifted in response to lithosphere extension and thinning. Migrating melts were likely produced by mantle upwelling and melting related to extension; they were modified from olivine-saturated to opx-saturated compositions, and caused different styles of melt-rock interaction (reactive spinel harzburgites, vs. impregnated plagioclase peridotites) depending on the lithospheric depths at which interaction occurred.

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Section: Composition Of Impregnating Meltssupporting

confidence: 65%

Section: Chemical Changes In Minerals: Evidence Of Trapped Melt Crystmentioning

confidence: 94%

Section: Chemical Changes In Minerals: Evidence Of Trapped Melt Crystmentioning

confidence: 99%

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Multi-stage melt–rock interaction in the Mt. Maggiore (Corsica, France) ophiolitic peridotites: microstructural and geochemical evidence

Rampone

Piccardo

Hofmann

2008

Contrib Mineral Petrol

110

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“…For this reason and considering that the Basal Gabbro Unit is not per se part of the main layered sequence of the Uitkomst Complex, we have largely ignored this unit for the purpose of the present paper. The composition of the parental magma can also be calculated from cumulus minerals, using suitable partition coefficients (Lambert & Simmons 1987, Loferski et al 1994, Mathez 1995, or from a putative trapped melt component (Bédard 1994). However, these methods have to correct for re-equilibration of the cumulus phases with trapped melt and zoning in some minerals, such as plagioclase and orthopyroxene.…”

Section: Age Datingmentioning

confidence: 99%

Parental Magma and Emplacement of the Stratiform Uitkomst Complex, South Africa

Waal¹,

Maier²,

Armstrong³

et al. 2001

The Canadian Mineralogist

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The Uitkomst Complex, a Ni-Cu-PGE-Cr-mineralized layered basic intrusion situated approximately 200 km due east of Pretoria, South Africa, hosts commercially viable magmatic base-metal sulfide deposits. The Complex has a concordant 207 Pb/ 206 Pb zircon age of 2044 ± 8 Ma, suggesting that it is coeval with the Rustenburg Layered Suite (RLS) of the Bushveld Complex. Chemical modeling, using summation and least-squares optimization techniques, provides evidence that the boninitic Bushveld B1 magma is parental to both the lower ultrabasic and upper basic layered series of the Uitkomst Complex. The layered series crystallized in two stages, i.e., a lower conduit and an upper closed-system stage. The tubular shape of the Uitkomst Complex is the result of the intersection of a near-horizontal bedding plane fault with an existing vertical fracture zone under tensional conditions. During the conduit stage, a combination of magma mixing, contamination and flow dynamics may have facilitated sulfide formation and segregation. The identification of Bushveld B1 magma as the major parental magma of the Uitkomst Complex has significance in the exploration for similarly mineralized sub-RLS intrusive bodies. Mots-clés: massif intrusif basique stratiforme, complexe de Uitkomst, minéralisation en Ni-Cu-PGE-Cr, mélange de magmas, ségrégation de sulfures, Afrique du Sud. §

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“…The chemical compositions of cumulates are principally controlled by the modal proportions of the cumulus minerals and interstitial melts trapped during crystallization (e.g., Maier and Barnes, 1998;Bédard, 1994). Assimilation of material from surrounding rocks may also play a significant role in magma evolution (e.g., DePaolo, 1981DePaolo, , 1985Huppert and Sparks, 1985;Marks and Markl, 2001).…”

Section: Introductionmentioning

confidence: 99%

Magma evolution in the upper part (Stage IV) of the Fongen-Hyllingen Layered Intrusion, central Norway

El-Rus

Wilson

Sørensen

2007

Journal of Mineralogical and Petrological Sciences

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The upper part (Stage IV) of the Fongen Hyllingen intrusion, southeast of Trondheim, Norway, comprises a ~ 1800 m thick sequence of cumulates showing a strong normal fractionation trend from olivine gabbros at the bottom through diorites to quartz bearing syenites at the roof. Mineral compositions show extreme ranges: olivine Fo 74−0 ; Ca rich pyroxene Mg#79 0; plagioclase An 60−0 . The cumulate sequence has been divided into five intervals based on cumulus assemblages. The summation method has been used to calculate successive magma compositions for these intervals based on whole rock major element chemical analyses of 49 samples. The most primitive calculated magma composition has 51.7% SiO 2 , 5.0% MgO, 5.3% total alkalis and a Mg number of 47.5; it lies near the base of the basaltic trachyandesite field in the Total Alkali Silica (TAS) diagram, very close to the dividing line between tholeiitic and alkaline suites. This magma evolved through the trachyandesite field into the trachyte field. The most evolved magma composition has ~ 11.4% alkalies; alkali enrichment is not due to assimilation of metapelites. There was very little iron enrichment during fractionation and magma density decreased continuously, enabling repeated influxes of new magma to pond and to elevate the resident melt, facilitating magma stratification. The parental magma may have resided in a lower crustal chamber where it differentiated before repeatedly supplying the overlying Fongen Hyllingen chamber.

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A procedure for calculating the equilibrium distribution of trace elements among the minerals of cumulate rocks, and the concentration of trace elements in the coexisting liquids

Cited by 259 publications

References 40 publications

Multi-stage melt–rock interaction in the Mt. Maggiore (Corsica, France) ophiolitic peridotites: microstructural and geochemical evidence

Multi-stage melt–rock interaction in the Mt. Maggiore (Corsica, France) ophiolitic peridotites: microstructural and geochemical evidence

Parental Magma and Emplacement of the Stratiform Uitkomst Complex, South Africa

Magma evolution in the upper part (Stage IV) of the Fongen-Hyllingen Layered Intrusion, central Norway

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