Emplacement of magmatic Cu-Au-Te(-Ni-PGE) sulfide blebs in alkaline mafic rocks of the Mordor Complex, Northern Territory, Australia

Mineralium Deposita ◽

10.1007/s00126-020-01015-2 ◽

2020 ◽

Author(s):

David A. Holwell ◽

Daryl E. Blanks

Keyword(s):

Aldan Shield ◽

Northern Territory ◽

Igneous Rocks ◽

Sulfide Liquid ◽

Alkaline Complex ◽

Mafic Rocks ◽

Igneous Complex ◽

Intimate Association ◽

Mantle Sources ◽

Low Degrees

Abstract Magmatic Ni-Cu-PGE sulfide mineralisation is mostly confined to tholeiitic to komatiitic mafic-ultramafic intrusions, yet there have been an increasing number of occurrences recorded in alkaline-ultramafic, post-collisional magmatic systems, particularly in the lower and middle crust that generally display a characteristic Cu-Au-Te enrichment over more conventional Ni-Cu(-PGE) mineralisation. The Mordor Alkaline Igneous Complex, Australia, is a mid-crustal, zoned alkaline complex comprised of a syenite body with an alkaline mafic-ultramafic subcomplex containing dunites, wehrlites and shonkinites. Sulfide mineralisation is present either in thin, PGE-enriched stratiform ‘reefs’ within layered ultramafics in the centre of the subcomplex, or in thicker zones of Cu(-Au-PGE-Te) sulfide hosted by phlogopite-rich shonkinites towards the intrusion margins. This latter style comprises blebs of pyrite, chalcopyrite and minor millerite and PGE tellurides formed from the cooling of a Cu-dominant sulfide liquid. Primary igneous calcite is present in intimate association with the sulfide. We note that the circular nature of the complex, with a dunite core and shonkinite rim with chalcophile element mineralisation, is comparable to the pipe-like, intracratonic, alkaline-ultramafic Aldan Shield intrusions in Russia. As such, Mordor may have an intracratonic rather than post-collisional affinity. Nevertheless, sulfide mineralisation is typical of other alkaline-hosted occurrences, with a Cu-Au-Te-rich signature, low Ni contents and textural association with calcite, supporting models of chalcophile metal and S fluxing alongside carbonate in alkaline systems derived from low degrees of partial melting of hydrous and carbonated mantle sources. Mordor illustrates that alkaline igneous rocks are prospective for magmatic Cu-Au-PGE-Ni sulfide mineralisation, and the classic ‘marginal base metal– and sulfide-rich’ and ‘stratiform PGE-rich and sulfide-poor’ mineralisation styles may both be found in such intrusions.

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40Ar/39Ar Geochronology of the Malyy (Little) Murun Massif, Aldan Shield of the Siberian Craton: A Simple Story for an Intricate Igneous Complex

10.20944/preprints201811.0470.v1 ◽

2018 ◽

Author(s):

Alexei V. Ivanov ◽

Nikolay V. Vladykin ◽

Elena I. Demonterova ◽

Viktor A. Gorovoy ◽

Emilia Yu. Dokuchits

Keyword(s):

Siberian Craton ◽

Middle Jurassic ◽

Aldan Shield ◽

Igneous Rocks ◽

Geochronological Data ◽

Igneous Complex ◽

Mineral Associations ◽

Ar Geochronology ◽

Hydrothermal Mineral ◽

Extensional Setting

The Malyy (Little) Murun massif of the Aldan Shield of the Siberian Craton has long been a kind of the geologists’ Siberian Mecca. It attracted thousands of geologists, prospectors and mineral collectors despite of its remote location. It is famous for a dozen of new and rare minerals, including gemstones charoite and dianite (the latter is the market name for strontian potassicrichrerite), as well as for specific alkaline igneous rocks. Despite of this, the age of the Malyy Murun igneous complex and associated metasomatic and hydrothermal mineral associations remained poorly constrained. In this paper, we provide extensive 40Ar/39Ar geochronological data to reveal its age and temporal history. It appeared that being unique in terms of rocks and constituent minerals, the Malyy Murun is one of multiple alkaline massifs and lavas emplaced in Early Cretaceous (~137-128 Ma) within a framework of extensional setting of the Aldan Shield and nearby Transbaikalian region. The extension has occurred 40-60 million years after the supposed closure of the Mongolia-Okhotsk Ocean and peak of orogeny in Early-Middle Jurassic.

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40Ar/39Ar Geochronology of the Malyy (Little) Murun Massif, Aldan Shield of the Siberian Craton: A Simple Story for an Intricate Igneous Complex

Minerals ◽

10.3390/min8120602 ◽

2018 ◽

Vol 8 (12) ◽

pp. 602

Author(s):

Alexei Ivanov ◽

Nikolay Vladykin ◽

Elena Demonterova ◽

Viktor Gorovoy ◽

Emilia Dokuchits

Keyword(s):

Early Cretaceous ◽

Siberian Craton ◽

Middle Jurassic ◽

Aldan Shield ◽

Igneous Rocks ◽

Geochronological Data ◽

Igneous Complex ◽

Mineral Associations ◽

Hydrothermal Mineral ◽

Extensional Setting

The Malyy (Little) Murun massif of the Aldan Shield of the Siberian Craton has long been a kind of Siberian Mecca for geologists. It has attracted thousands of geologists, prospectors, and mineral collectors despite its remote location. It is famous for a dozen new and rare minerals, including the gemstones charoite and dianite (the latter is the market name for strontian potassicrichrerite), as well as for a range of uncommon alkaline igneous rocks. Despite this, the age of the Malyy Murun igneous complex and associated metasomatic and hydrothermal mineral associations has remained poorly constrained until now. In this paper, we provide extensive 40Ar/39Ar geochronological data to reveal its age and temporal history. It appears that, although unique in terms of rocks and constituent minerals, the Malyy Murun is just one of multiple alkaline massifs and lavas emplaced in the Early Cretaceous (~137–128 Ma) within a framework of the extensional setting of the Aldan Shield and nearby Transbaikalian region. The extension took place 40–60 million years after the supposed closure of the Mongolia–Okhotsk Ocean and orogenic peak in the Early–Middle Jurassic.

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The Metamorphosed Limestones and Associated Contaminated Igneous Rocks of the Carlingford District, Co. Louth

Geological Magazine ◽

10.1017/s0016756800097223 ◽

1932 ◽

Vol 69 (5) ◽

pp. 209-233 ◽

Cited By ~ 5

Author(s):

G. D. Osborne

Keyword(s):

Igneous Rocks ◽

The South ◽

Ordnance Survey ◽

Igneous Complex ◽

North East ◽

The North ◽

South West ◽

Carboniferous Limestone ◽

Contamination Effects

THE Carlingford-Barnave district falls within the boundaries of Sheet 71 of the Ordnance Survey of Ireland, and forms part of a broad promontory lying between Carlingford Lough on the north-east and Dundalk Bay on the south-west. The greater part of this promontory is made up of an igneous complex of Tertiary age which has invaded the Silurian slates and quartzites and the Carboniferous Limestone Series. This complex has not yet been investigated in detail, but for the purposes of the present paper certain references to it are necessary, and these are made below. The prevalence of hybrid-relations and contamination-effects between the basic and acid igneous rocks of the region is a very marked feature, and because of this it has been difficult at times to decide which types have been responsible for the various stages of the metamorphism.

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Fenitization of layered mafic rocks in the Lillebukt alkaline complex, Stjernoy, Norway

Lithos ◽

10.1016/0024-4937(80)90022-5 ◽

1980 ◽

Vol 13 (2) ◽

pp. 215 ◽

Cited By ~ 1

Author(s):

K. Kjøsnes

Keyword(s):

Alkaline Complex ◽

Mafic Rocks

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Geochemistry of bimodal amphibolitic—felsic gneiss complexes from eastern Massif Central, France

Geological Magazine ◽

10.1017/s0016756800013637 ◽

1995 ◽

Vol 132 (3) ◽

pp. 321-337 ◽

Cited By ~ 14

Author(s):

Bernard Briand ◽

Jean-Luc Bouchardon ◽

Houssa Ouali ◽

Michel Piboule ◽

Paul Capiez

Keyword(s):

Crustal Contamination ◽

Igneous Rocks ◽

Chemical Characteristics ◽

Continental Margins ◽

High Grade ◽

Transitional Stage ◽

Crust Formation ◽

Massif Central ◽

Mantle Sources ◽

Two Populations

AbstractHigh-grade basic and acidic meta-igneous rocks are widespread in the bimodal amphibolitic—felsic gneiss complexes, which are characteristic formations of the ‘Middle Allochthonous Unit’ from eastern and southern French Massif Central. The metabasites from the Lyonnais and Doux complexes are chemically diverse and range from N-MORB type tholeiitic to transitional types. The two populations are not related by fractional crystallization or crustal contamination processes and their chemical characteristics reflect differences in their mantle sources. An ensialic setting is supported by the crustally-derived character of some of the associated felsic rocks, but the presence of N-MORB-type metabasites argues for an extensional environment. This bimodal association compares well with the magmatism of rifted continental margins and may reflect a transitional stage between continental rifting and oceanic crust formation during the Cambro-Ordovician spreading event.

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An Overview of the Carbonatites from the Indian Subcontinent

Open Geosciences ◽

10.1515/geo-2020-0007 ◽

2020 ◽

Vol 12 (1) ◽

pp. 85-116 ◽

Cited By ~ 2

Author(s):

Kirtikumar Randive ◽

Tushar Meshram

Keyword(s):

Sri Lanka ◽

Indian Subcontinent ◽

Source Rocks ◽

Time Range ◽

Alkaline Complex ◽

Comprehensive Information ◽

Igneous Origin ◽

Continental Rifts ◽

Low Degrees ◽

Orogenic Belts

AbstractCarbonatites are carbonate-rich rocks of igneous origin. They form the magmas of their own that are generated in the deep mantle by low degrees of partial melting of carbonated peridotite or eclogite source rocks. They are known to occur since the Archaean times till recent, the activity showing gradual increase from older to younger times. They are commonly associated with alkaline rocks and be genetically related with them. They often induce metasomatic alteration in the country rocks forming an aureole of fenitization around them. They are host for economically important mineral deposits including rare metals and REE. They are commonly associated with the continental rifts, but are also common in the orogenic belts; but not known to occur in the intra-plate regions. The carbonatites are known to occur all over the globe, majority of the occurrences located in Africa, Fenno-Scandinavia, Karelian-Kola, Mongolia, China, Australia, South America and India. In the Indian Subcontinent carbonatites occur in India, Pakistan, Afghanistan and Sri Lanka; but so far not known to occur in Nepal, Bhutan, Bangladesh and Myanmar. This paper takes an overview of the carbonatite occurrences in the Indian Subcontinent in the light of recent data. The localities being discussed in detail cover a considerable time range (>2400 Ma to <0.6 Ma) from India (Hogenakal, Newania, Sevathur, Sung Valley, Sarnu-Dandali and Mundwara, and Amba Dongar), Pakistan (Permian Koga and Tertiary Pehsawar Plain Alkaline Complex which includes Loe Shilman, Sillai Patti, Jambil and Jawar), Afghanistan (Khanneshin) and Sri Lanka (Eppawala). This review provide the comprehensive information about geochemical characteristics and evolution of carbonatites in Indian Subcontinent with respect to space and time.

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The Tethyan Himalaya igneous province: Early melting products of the Kerguelen mantle plume

Journal of Petrology ◽

10.1093/petrology/egab069 ◽

2021 ◽

Author(s):

Sheng-Sheng Chen ◽

Wei-Ming Fan ◽

Ren-Deng Shi ◽

Ji-Feng Xu ◽

Yong-Min Liu

Keyword(s):

Mantle Plume ◽

Crustal Contamination ◽

Large Igneous Province ◽

Mafic Rocks ◽

Os Isotopes ◽

Igneous Province ◽

Break Up ◽

Low Degrees ◽

The Relationship ◽

Tethyan Himalaya

Abstract The Kerguelen large igneous province (LIP) has been related to mantle plume activity since at least 120 Ma. There are some older (147–130 Ma) magmatic provinces on circum-eastern Gondwana, but the relationship between these provinces and the Kerguelen mantle plume remains controversial. Here we present petrological, geochronological, geochemical, and Sr–Nd–Hf–Pb–Os isotopic data for high-Ti mafic rocks from two localities (Cuona and Jiangzi) in the eastern Tethyan Himalaya igneous province (147–130 Ma). Zircon grains from these two localities yielded concordant weighted mean 206Pb/238U ages of 137.25 ± 0.98 and 131.28 ± 0.78 Ma (2σ), respectively. The analyzed mafic rocks are enriched in high field strength elements and have positive Nb–Ta anomalies relative to Th and La, which have ocean island basalt-like characteristics. The Cuona basalts were generated by low degrees of melting (3–5%) of garnet lherzolites (3–5 vol.% garnet), and elsewhere the Jiangzi diabases were formed by relatively lower degrees of melting (1–3%) of garnet lherzolite (1–5 vol.% garnet). The highly radiogenic Os and Pb isotopic compositions of the Jiangzi diabases were produced by crustal contamination, but the Cuona basalts experienced the least crustal contamination given their relatively low γOs(t), 206Pb/204Pbi, 207Pb/204Pbi, and 208Pb/204Pbi values. Major and trace element geochemical and Sr–Nd–Hf–Pb–Os isotope data for the Cuona basalts are similar to products of the Kerguelen mantle plume head. Together with high mantle potential temperatures (>1500°C), this suggests that the eastern Tethyan Himalaya igneous province (147–130 Ma) was an early magmatic product of the Kerguelen plume. A mantle plume initiation model can explain the temporal and spatial evolution of the Kerguelen LIP, and pre-continental break-up played a role in the breakup of eastern Gondwana, given the >10 Myr between initial mantle plume activity (147–130 Ma) and continental break-up (132–130 Ma). Like studies of Re-Os isotopes in other LIPs, the increasing amount of crustal assimilation with distance from the plume stem can explain the variations in radiogenic Os.

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Calcium isotopic evidence for the mantle sources of carbonatites

Science Advances ◽

10.1126/sciadv.aba3269 ◽

2020 ◽

Vol 6 (23) ◽

pp. eaba3269 ◽

Cited By ~ 2

Author(s):

Elsa Amsellem ◽

Frédéric Moynier ◽

Hervé Bertrand ◽

Amaury Bouyon ◽

João Mata ◽

...

Keyword(s):

Mantle Source ◽

Igneous Rocks ◽

Isotopic Ratios ◽

Carbonate Minerals ◽

Isotopic Evidence ◽

Calcium Isotopes ◽

Mantle Sources ◽

Marine Carbonates ◽

Carbonate Materials ◽

Silicate Rocks

The origin of carbonatites—igneous rocks with more than 50% of carbonate minerals—and whether they originate from a primary mantle source or from recycling of surface materials are still debated. Calcium isotopes have the potential to resolve the origin of carbonatites, since marine carbonates are enriched in the lighter isotopes of Ca compared to the mantle. Here, we report the Ca isotopic compositions for 74 carbonatites and associated silicate rocks from continental and oceanic settings, spanning from 3 billion years ago to the present day, together with O and C isotopic ratios for 37 samples. Calcium-, Mg-, and Fe-rich carbonatites have isotopically lighter Ca than mantle-derived rocks such as basalts and fall within the range of isotopically light Ca from ancient marine carbonates. This signature reflects the composition of the source, which is isotopically light and is consistent with recycling of surface carbonate materials into the mantle.

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