M and Mg values in igneous rocks: proposed usage and a comment on currently employed Fe2O3 corrections

Hughes, C.J.; Hussey, E. M.

doi:10.1016/0016-7037(76)90015-6

Cited by 34 publications

(7 citation statements)

References 11 publications

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“…Mg values (Hughes & Hussey 1976) between 50 and 65 are also comparable to those of ocean floor basalts. However, the samples have higher Na,O and lower Mg values compared to primitive ocean floor basalts (Blanchard et al 1976;Langmuir et al 1977) which may be due either to alteration or to the evolved nature of the samples (Green 1971).…”

Section: Pillow Lavamentioning

confidence: 99%

Chemical characters of volcanic rocks from Andaman ophiolite, India

Ray

Sengupta

Hul³

1988

JGS

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Two parallel belts of late Mesozoic ophiolitic rocks occur along the outer arc ridge and inner volcanic line of the Indonesian arc system. The northernmost occurrence along the outer arc ridge is in the Andaman group of islands where ophiolitic rocks occur as dismembered slices emplaced over Eocene to Oligocene turbidites.Volcanic members of the ophiolitic suite occur in two thrust slices, one consisting only of pillow basalts while the other is made up of basalts, basaltic andesites and acid differentiates. Certain chemical characters of the basaltic components are comparable to MAR basalts at 45" N. On the basis of comparable REE patterns and the presence of appreciable volumes of acid differentiates, they are further suggested to represent marginal basin crust. Variable (La/Ce), and (La/Sm), ratios in these basalts are interpreted in terms of a heterogeneous source.The basaltic melts have undergone extensive fractional crystallization of clinopyroxene, olivine and plagioclase to produce basaltic andesite and acid volcanic rocks. Between the parent and the differentiates, there is no appreciable change in (Ce/Yb), ratio or HREE abundance level, suggesting low pressure fractionation in a shallow magma chamber, possibly beneath a slow spreading centre.

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Section: Pillow Lavamentioning

confidence: 99%

Chemical characters of volcanic rocks from Andaman ophiolite, India

Ray

Sengupta

Hul³

1988

JGS

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“…Mafic components were low, the FeO+MgO+TiO2 sum being comprised between 1.71 and 3.12 wt% in the granites, and slightly higher in the greisens (1.80 to 5.39 wt%, with an outlier at 14.04 wt%), the highest values in the latter being, however, mostly due to a sulfide component (mainly, pyrite and arsenopyrite, with S and As contents of several 1000 ppm) in the mineral assemblage. All the rocks are magnesium poor, with the M index [57] (M = 100 Mg/Mg + ∑Fe) between 3 and 31, higher (M from 15 to 31) in the granites than in the greisens (M from 3 to 15). Note that there is less apatite in greisens than in granites.…”

Section: Major Elementsmentioning

confidence: 99%

“…Any attempt to disentangle alteration and magmatic effects must await the discussion below. [15][16][17][18]57,58]. Inserts: definition of alteration vectors.…”

Section: Major Elementsmentioning

confidence: 99%

The Panasqueira Rare Metal Granite Suites and Their Involvement in the Genesis of the World-Class Panasqueira W–Sn–Cu Vein Deposit: A Petrographic, Mineralogical, and Geochemical Study

et al. 2020

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Elucidation of time-space relationships between a given wolframite deposit and the associated granites, the nature of the latter, and their alterations, is a prerequisite to establishing a genetic model. In the case of the world-class Panasqueira deposit, the problem is complicated because the associated granites are concealed and until now poorly known. The study of samples from a recent drill hole and a new gallery allowed a new approach of the Panasqueira granite system. Detailed petrographic, mineralogical, and geochemical studies were conducted, involving bulk major and trace analyses, BSE and CL imaging, EPMA, and SEM-EDS analyses of minerals. The apical part of the Pansqueira pluton consisted of a layered sequence of separate granite pulses, strongly affected by polyphase alteration. The use of pertinent geochemical diagrams (major and trace elements) facilitated the discrimination of magmatic and alteration trends. The studied samples were representative of a magmatic suite of the high-phosphorus peraluminous rare-metal granite type. The less fractionated members were porphyritic protolithionite granites (G1), the more evolved member was an albite-Li-muscovite rare metal granite (G4). Granites showed three types of alteration processes. Early muscovitisation (Ms0) affected the protolithionite in G1. Intense silicification affected the upper G4 cupola. Late muscovitisation (Fe–Li–Ms1) was pervasive in all facies, more intense in the G4 cupola, where quartz replacement yielded quartz-muscovite (pseudo-greisen) and muscovite only (episyenite) rocks. These alterations were prone to yield rare metals to the coeval quartz-wolframite veins.

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“…The major dement compositions listed in Table 2 Hughes and Hussey, 1976) varying from 62 to 55. These rocks could not be classified using the classical alkali versus SiO2 graph as they are spilitized, but their normative compositions include hypersthene + quartz or olivine and confirm the tholeiitic character suggested on the basis of clinopyroxene compositions.…”

Section: Major Elementsmentioning

confidence: 99%

Geochemistry and geotectonic setting of Late Proterozoic Katangan basic rocks from Kibambale in central Shaba (Zaire)

Kampunzu¹,

Kanika²,

Kapenda³

et al. 1993

Geol Rundsch

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The Late Proterozoic Katangan basic rocks (dolerites and basalts) outcropping at Kibambale in central Shaba (Zaire) are classified as extension-related tholeiites. The concentrations of immobile major and trace elements resemble those encountered in Phanerozoic enriched oceanic ridge basalts (E-MORB) emplaced in incipient oceanic rifts such as Red Sea and Tadjura Gulf troughs. This conclusion is also sustained by: elemental ratios which are MORB-like; multielement chondrite-and MORB-normalized patterns; sedimentological data, especially the shallow water conditions which prevailed during the deposition of lower Kundelungu tillite in which these basic rocks are interstratified; and the geological and structural framework, notably the emplacement of these igneous rocks in a basin not distant from the Kibaran continental land mass.In this area the geological units containing the igneous rocks are not affected by significant tangential tectonism and so the present structural relationships are relatively undisturbed compared with those which prevailed during the emplacement of the igneous rocks.

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M and Mg values in igneous rocks: proposed usage and a comment on currently employed Fe2O3 corrections

Cited by 34 publications

References 11 publications

Chemical characters of volcanic rocks from Andaman ophiolite, India

Chemical characters of volcanic rocks from Andaman ophiolite, India

The Panasqueira Rare Metal Granite Suites and Their Involvement in the Genesis of the World-Class Panasqueira W–Sn–Cu Vein Deposit: A Petrographic, Mineralogical, and Geochemical Study

Geochemistry and geotectonic setting of Late Proterozoic Katangan basic rocks from Kibambale in central Shaba (Zaire)

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