Geochemical variability and origin of gabbroid to dioritoid rocks of the Železné hory Plutonic Complex

AbstractThe transition zone between 100 % dykes and high-level plutonic rocks of the Solund-Stavfjord Ophiolite Complex is complex due to the existence of many lithologies with different and variable contact relationships. The rocks of the plutonic complex vary in composition from FeTi basaltic to quartz dioritic, and the grain sizes vary from fine to pegmatitic. Felsic varieties are produced by fractional crystallization of basaltic magma as demonstrated by geochemical evolution and by gradual transition from gabbro to quartz diorite. Patches of fractionated dioritic rocks may show both gradual and intrusive relationships with the surrounding host gabbro. This demonstrates that late-stage liquids commonly left the source region and locally intruded the surrounding parent rocks. The high-level plutonic rocks are thoroughly epidotized and are cut by dykes consisting of granoblastic epidote and quartz. The high-level plutonic complex is associated with irregular bodies of fine- to medium-grained plagioclase-porphyritic diabase of high MgO content. These diabase bodies are intruded by dykes that become progressively more regular in shape. The plutonic complex locally shows intrusive relationships with the overlying 100% dyke complex, but is itself cut by two dyke swarms. The dykes of the first swarm formed while the plutonic complex experienced sinistral shear strain, and the dykes are generally less regular and thinner than the dykes of the second swarm. This indicates that the dykes of the first swarm intruded while the rocks of the plutonic complex were still hot, while the next dyke swarm intruded later when the rock complex was colder. Dykes of both swarms range in composition from slightly to strongly fractionated, suggesting that the magma chambers they were expelled from underwent significant fractionation in between magma replenishment. Numerous dykes of both swarms carry large quantities of glomeroporphyritic aggregates of plagioclase and altered clinopyroxene, indicating that the source area to the dykes very often was a crystal mush.

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Geochronology of granites of the western Korosten AMCG complex (Ukrainian Shield): implications for the emplacement history and origin of miarolitic pegmatites

European Journal of Mineralogy ◽

10.5194/ejm-33-703-2021 ◽

2021 ◽

Vol 33 (6) ◽

pp. 703-716

Author(s):

Leonid Shumlyanskyy ◽

Gerhard Franz ◽

Sarah Glynn ◽

Oleksandr Mytrokhyn ◽

Dmytro Voznyak ◽

...

Keyword(s):

Economic Value ◽

Ukrainian Shield ◽

Western Region ◽

The South ◽

Anorthosite Massif ◽

Granitic Intrusion ◽

Plutonic Complex ◽

Flow Through ◽

Basic Rocks ◽

North Western

Abstract. The origin of large miarolitic (also known as “chamber”) pegmatites is not fully understood although they may have great economic value. The formation of cavities in magmatic bodies is related to melt degassing and gas or fluid flow through partially solidified magma. In this paper, the origin of the Volyn pegmatite field, located in the Palaeoproterozoic Korosten anorthosite–mangerite–charnockite–granite (AMCG) complex, North-Western region of the Ukrainian Shield, is discussed. Pegmatites of the field host deposits of piezoelectric quartz that is accompanied by gem-quality beryl and topaz. The Volyn pegmatite field is confined to granites located in the south-western part of the Korosten complex and extends for 22 km along the contact with the anorthosite massif within the Korosten plutonic complex. Geological data indicate hybridization of basic melts and partly crystallized granites, as well as direct impact of fluids derived from basic melts on the chamber pegmatites. The new U–Pb zircon ages obtained for granites and pegmatites of the Korosten complex confirm that the rock assemblage in the northern part of the complex crystallized between 1800 and 1780 Ma, whereas rocks in the southern part intruded mainly between 1768 and 1755 Ma. U–Pb zircon ages for granites from the south-western part of the Korosten complex indicate that granites were emplaced at 1770–1765 Ma, a few million years prior to the intrusion of the gabbro–anorthosite massif (1762–1758 Ma), while chamber pegmatites in these granites crystallized at 1760 ± 3 Ma, coevally with the basic rocks. Ultimately, the formation of the chamber pegmatites was related to the reheating of the semi-crystallized granitic intrusion and to fluids migrating from the underlying gabbro–anorthosite massif.

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Trace-element study and uranium-lead dating of perovskite from the Afrikanda plutonic complex, Kola Peninsula (Russia) using LA-ICP-MS

Mineralogy and Petrology ◽

10.1007/s00710-010-0131-9 ◽

2010 ◽

Vol 100 (3-4) ◽

pp. 95-103 ◽

Cited By ~ 19

Author(s):

Ekaterina P. Reguir ◽

Alfredo Camacho ◽

Panseok Yang ◽

Anton R. Chakhmouradian ◽

Vadim S. Kamenetsky ◽

...

Keyword(s):

Trace Element ◽

Kola Peninsula ◽

Icp Ms ◽

Plutonic Complex ◽

Trace Element Study ◽

Uranium Lead Dating ◽

Element Study

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Ti-substitution mechanism in plutonic oxy-kaersutite from the Larvik alkaline complex, Oslo rift, Norway

Mineralogical Magazine ◽

10.1180/0026461046840215 ◽

2004 ◽

Vol 68 (4) ◽

pp. 687-697 ◽

Cited By ~ 2

Author(s):

H. Satoh ◽

Y. Yamaguchi ◽

K. Makino

Keyword(s):

Negative Correlation ◽

Closed System ◽

Mineral Chemistry ◽

Formula Unit ◽

Alkaline Complex ◽

Crustal Thinning ◽

Substitution Mechanism ◽

Plutonic Complex ◽

O Isotope ◽

Ti Substitution

AbstractAmphibole in the Larvik alkaline plutonic complex in the Oslo rift, Norway, has Ti-rich compositions from edenite through pargasite to kaersutite, and has a large H+ deficiency (0.7–1.1 atoms per formula unit: a.p.f.u.) with a large oxy component in the amphibole OH– site (O2– = 2 – (OH + F + Cl) = 0.2–0.9 a.p.f.u.), similar to the mantle-derived kaersutites. Their compositions reveal a characteristically low Fe3+/(Fe3++Fe2+) ratio (<0.23) and a high F concentration (0.3–0.9 a.p.f.u.). Correlation with the Fe3+ ratio caused by Fe2+ + OH– = Fe3+ + O2– + 1/2H2 substitution is negligible, which is supported by H and O isotope compositions. A possible substitution, [6]Al3+ + OH– = [6]Ti4+ + O2– may be operative for Larvik kaersutites when the O2–/Ti is 1.0. A relatively larger O2–/Ti ratio (1.2—2.0) suggests an another kaersutite substitution mechanism, [6]R2+ + 2OH– = [6]Ti4+ + 2O2–, where [6]R2+ = Fe2+ + Mg + Mn. These effects might result in the limited O2–/Ti ratio value from 1.0 to 2.0.A negative correlation between Ti and F, suggesting F incorporation into kaersutite may diminish the O2–/Ti ratio, not only due to the occupation of this non-oxy species in the O3 site, but also due to F—Ti avoidance. Composition-dependent H and O isotope variations (δD = –106 to –71% and δ18O = 4.6–5.2%) suggest equilibrium in the closed-system magma with differentiation. The mineral chemistry of Larvik oxy-kaersutitic amphibole could reflect the crystallization in a closed-system magma during rifting with passive crustal thinning at the Oslo palaeorift.

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