Geochemistry and origin of massif-type anorthosites

Simmons, E. Craig; Hanson, Gilbert N.

doi:10.1007/bf00372151

Cited by 70 publications

(21 citation statements)

References 32 publications

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“…The low K/Rb ratios are probably due to secondary processes as Rb does not correlate with other Incompatible but less mobile elements such as La and Zr. The Ba content Is commonly within the range reported for equivalent rocks from other Grenvllllan anorthositlc massifs (Simmons and Hanson, 1978).…”

Section: Trace Elements Anorthosite Complexsupporting

confidence: 73%

“…They are the result mainly of plagioclase accumulation as suggested by their texture, mineralogy, high AI2O3 and Sr content, high Ca0/Na20, Na20/K20 and Sr/Ba ratios and low REE abundances, accompanied by chondrItenormal Ized patterns showing distinct Simmons and Hanson (1978) and Irving (1978). Figure 4 shows the calculated REE concentration in parental magmas of anorthosite (41), anorthosltic gabbro (21) and pyroxene bearing rock (530).…”

Section: Discussionmentioning

confidence: 99%

“…The rocks of the anorthositic complex are characterized by a low SI02 content (<57%) and low MgO/FeOtot and K20/Na20 ratios, features typical of anorthositic suites In general (Simmons and Hanson, 1978 2) fall Into or close to the fields of Martignole (1974) with calculated values for "pure" anorthosites (100% plagioclase), "pure" dunites (100% olivine) and troctolits (50% plagioclase + 50% olivine). Solid lines are tie lines between olivine and plagioclase in equl I Ibrlm; dashed I Ines del ineate the fields for anorthosites (A), anorthosites-Ieuconorites (B) and leucotroctoiites-olivine gabbros (C) as defined by Martignole (1974 abundances.…”

Section: Major Elements Anorthosite Complexmentioning

confidence: 95%

“…Reynolds a! al^ 1969, Simmons andHanson, 1978). The K/Rb ratio Is highly variable (120-1350) although generally low (<400) compared to the high values typical of Grenvllllan anorthositlc suites (Reynolds si a_L.…”

Section: Trace Elements Anorthosite Complexmentioning

confidence: 97%

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Anorthosltes and Gabbroic Bodies in northern Cape Breton Island, Nova Scotia

Dupuy¹,

Dostál

Smith

et al. 1986

atgeol

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Several lensoidal anorthositic bodies of probable Precaabrian age, are exposed in northern Cape Breton Island within a central fault-banded block of quartzofeldspathlc gneisses. One of these, the Red River anorthoslts coaplex Cell ka long and up to 1 ka Hide) ranges free anorthosite to anorthositlc gabbro with high Al2O3 and Sr contents and large positive Eu anomalies resulting mainly from plagloolase accumulation. Following an episode of polyphase deformation and amphilbolite facles metamorphism, a monzodlorite-gabbro body of unknown age was intruded into both the anorthosite and Its host rocks. The geochemistry of this Intrusion indicates that It Is calc-alkaline. Granite sheets, Intrusive Into the aonzodlorlte-gabbro body, do not appear to be comagmatic based upon the trace element chemistry. These sheets may be correlated with granitic plutons in the Cape North area which have been dated at 330 ±23 Ma. RÉSUMÉ Plusieurs masses anorthositiques, vraisemblablement d'âge précambrien, affieurent de manière lentlculaire eu sein d'un amas central de gneiss quartzofeldspathique, bordé par des failles, dans la nord de l’ile du Cap-Breton. Paral celles-ci, le compiexe d'anorthosite de Red River (d'environ 11 ka da longueur et jusqu'à 1 km de largsur) s'étage des anorthosites aux gabbros anorthositlques, montre de haute contenus en Al2O3 et Sr et a fouml des anomalies élevées en Eu résultant prlncipalament de L’accummulation des plagloclasses. Aprte un épisode de déformation polyphasée et métamorphisme au faciès amphibolite, un corps de monzonite et gabbro d'âge inconnu s'est introduit tant dans l'anorthosite que dans ses ancalssants. La géochimis de cette intrusion trahit une nature calco-alcaline. La chimie des éléments en traces tend à nier le comagmatisme des granites en nappe intruslfs dans le corps de monzodiorite-gabbro. Ceux-ci s'apparentent plutôt aux plutons granitiques dans la région de Cape North qui sent dates à 330 ±23 Ma. [Traduit par le journal]

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Section: Trace Elements Anorthosite Complexsupporting

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Section: Major Elements Anorthosite Complexmentioning

confidence: 95%

Section: Trace Elements Anorthosite Complexmentioning

confidence: 97%

See 2 more Smart Citations

Anorthosltes and Gabbroic Bodies in northern Cape Breton Island, Nova Scotia

Dupuy¹,

Dostál

Smith

et al. 1986

atgeol

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“…This trend reflects the gradational change in modal proportions of primary cumulates plagioclase and pyroxene (e.g. Simmons and Hanson, 1978). The trends of the Khamal anorthositegabbro complex (Fig.…”

Section: Major Elements Characteristics Of the Wadi Khamal Complexmentioning

confidence: 82%

Geology and Lithostratigraphy of the Ultramafic-Mafic Rocks and Associated Mineralizations, Wadi Khamal Area, West-Central Arabian Shield

Harbi¹

2008

ear

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Abstract. Field, petrography and major elements geochemistry of the ultramafic -mafic rocks of Wadi Khamal area led to the recognition of the following rock groups, namely: 1) ophiolitic suite, melagabbronorite and cumulate gabbronorite to the south of Wadi Mahalah (southern ultramafic-mafic rocks) and 2) Wadi Khamal anorthositegabbro complex to the north.The ophiolitic rocks in the southern area include serpentinites, peridotites and pyroxenites. The serpentinites contain large blocks of amphibolites, schists, gneisses, and metagabbros. These rocks were intruded by melagabbronorite and cumulate gabbronorite. On the AFM diagram, these rocks plot along the MgO-FeO* side in the tholeiitic field except those of the melagabbronorite which plot within the calcalkaline field.The Wadi Khamal complex consists of four major units; marginal gabbro unit, anorthosite unit, central gabbroic unit and northern gabbronorite unit. The marginal gabbro unit and anorthosite unit have a calc alkaline differentiation trend while those of the central gabbro unit (olivine gabbro, melagabbronorite and Fe-Ti oxides-apatite gabbronorite) and the northern gabbronorite show a distinct different trend parallel to the FeO*-MgO side line and belong to the tholeiitic differentiation trend. Based on major element geochemistry, the southern ultramafic -mafic rocks were derived from a more mafic liquid source rather different from magma source(s) which formed the Khamal anorthosite-gabbro complex.The Fe-Ti oxides-apatite gabbronorite of the central unit of the Khamal complex hosts two main types of Fe-Ti oxide ores. 1) Massive bands of nelsonite ore consist mainly of magnetite, ilmenite, apa-H.M. Harbi 120 tite and minor amounts of silicates. It occurs in the form of bands and lenses of variable sizes intercalated with the magnetite-ilmeniteapatite gabbronorite, and 2) massive magnetite-ilmenite ore, which is less abundant compared to the nelsonite. The latter occurs as dyke-like bodies with nelsonite selvages within the anorthosite, or as bands or lenses enclosed within the nelsonite and close to the contact with the overlying anorthosite cap. The contact of magnetite-ilmenite ore with the nelsonite bands is gradational. The close spatial association and mineralogical similarities between the Fe-Ti oxides -apatite gabbronorite and the nelsonite, as well as the variable Fe-Ti oxides/apatite ratios suggest that the nelsonite was formed as accumulations due to in situ fractional crystallization of Fe, Ti, P and volatiles-rich gabbroic magma. The formation of the massive magnetite-ilmenite ore is attributed to high fO 2 and mobility which promote later injection into the anorthosite host rocks.

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Magmatism in Extensional Structural Settings

Kampunzu¹,

Lubala²

1991

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Geochemistry and origin of massif-type anorthosites

Cited by 70 publications

References 32 publications

Anorthosltes and Gabbroic Bodies in northern Cape Breton Island, Nova Scotia

Anorthosltes and Gabbroic Bodies in northern Cape Breton Island, Nova Scotia

Geology and Lithostratigraphy of the Ultramafic-Mafic Rocks and Associated Mineralizations, Wadi Khamal Area, West-Central Arabian Shield

Magmatism in Extensional Structural Settings

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