Mineral textures of olivine minette and their significance for crystallization history of parental magma; an example from the Moldanubian Zone (the Bohemian Massif)

2019 ◽  
Vol 113 (4) ◽  
pp. 477-491 ◽  
Author(s):  
Šárka Kubínová ◽  
Shah Wali Faryad
Keyword(s):  
Bohemian Massif ◽  
Parental Magma ◽  
Moldanubian Zone ◽  
History Of

The Spačice eclogite: constraints on the P–T–t history of the Gföhl granulite terrane, Moldanubian Zone, Bohemian Massif

2005 ◽  
Vol 86 (3-4) ◽  
pp. 203-220 ◽  
Author(s):  
L. G. Medaris ◽  
E. D. Ghent ◽  
H. F. Wang ◽  
J. H. Fournelle ◽  
E. Jelínek
Keyword(s):  
Bohemian Massif ◽  
Moldanubian Zone ◽  
History Of

scholarly journals Petrology, mineral chemistry, and geochemistry of Late Triassic Ni–Cu ore-bearing mafic–ultramafic intrusions, Hongqiling, northeastern China: petrogenesis and tectonic implications

2019 ◽  
Vol 56 (2) ◽  
pp. 111-128
Author(s):  
Ai Li ◽  
Jian Wang ◽  
Yue Song
Keyword(s):  
Crustal Contamination ◽  
Parental Magma ◽  
Mineral Chemistry ◽  
Late Triassic ◽  
Sulfide Deposit ◽  
Chemical Compositions ◽  
Tholeiitic Magma ◽  
Average Value ◽  
Central Asian ◽  
History Of

The Hongqiling magmatic Ni–Cu sulfide deposit, situated on the southern margin of the eastern Central Asian Orogenic Belt (CAOB), is composed of over 30 mafic–ultramafic intrusions. These ore-bearing intrusions are composed mainly of harzburgite, lherzolite, websterite, orthopyroxenite, and norite (gabbro). The constituent minerals are olivine, diopside, bronzite, calcic-hornblende, plagioclase, and spinel with orthopyroxene as a dominant mineral in these intrusions. These ore-bearing intrusions are not Alaskan-type complexes. Spinel and clinopyroxene both exhibit different chemical compositions from those in the Alaskan-type complexes. The rocks that make up the intrusions have high contents of MgO (average value = 25.20 wt.%) and low TiO2 (average value = 0.58 wt.%). The high MgO contents of the minerals and the high Mg# (71) of the calculated melt in equilibrium with olivine demonstrate that the parental magma of the Hongqiling mafic–ultramafic intrusions was a high-Mg tholeiitic magma. The Hongqiling ore-bearing mafic–ultramafic intrusions and the calculated “trapped liquids” for the olivine-orthopyroxene cumulate rocks are all enriched in large-ion lithophile elements and depleted in high field strength elements. The Ce/Pb, Ta/La, Th/Yb, and (La/Sm)PM values and the depletion of Nb and Ta suggest that the magma experienced crustal contamination. The Hongqiling ore-bearing intrusions display many similarities with mafic–ultramafic intrusions that formed in a post-collisional extensional environment in the western CAOB (e.g., Huangshanxi). Common features include their whole-rock compositions and mineral chemistry. Combined with the evolutionary history of the eastern segment of the CAOB, we believe that the Late Triassic Hongqiling mafic–ultramafic intrusions formed in a post-collisional extensional environment.

Caledonian magmatism record within Hebridean Terrane? Loch Roag dyke (Lewis Island, northern Scotland) non-peridotitic xenoliths and megacrysts as messengers from deep lithosphere.

2020 ◽  
Author(s):  
Daniel Buczko ◽  
Magdalena Matusiak-Małek ◽  
Brian J. G. Upton ◽  
Theodoros Ntaflos ◽  
Sonja Aulbach ◽  
...  
Keyword(s):  
North Atlantic ◽  
Parental Magma ◽  
Geological Structure ◽  
Trace Element Composition ◽  
Isotopic Ratios ◽  
The North ◽  
Source Regions ◽  
Mantle Sources ◽  
History Of ◽  
North Atlantic Craton

<p>The northernmost part of Scotland – the Hebridean Terrane – is formed of Archean rocks originally being part of the Laurentian North Atlantic Craton. The geological history of the terrane is well recognised, however details of its internal structure remain unknown. The Eocene (Faithfull et al. 2012, JGS) Loch Roag monchiquite (Lewis Island) sampled deep-seated lithologies, providing insight on evolution and geological structure of the deeper lithosphere of the Hebridean terrane. The monchiquite comprises abundant xenoliths of ultramafic, mafic and felsic rocks. The peridotitic xenoliths represent pieces of Archean mantle underlying marginal parts of the North Atlantic Craton, whereas the origin of non-peridotitic lithologies is uncertain.</p><p>The studied suite of samples comprises two groups: 1) “xenoliths” of diorites (plagioclase, clinopyroxene, orthopyroxene, apatite, opaques) and biotite clinopyroxenites (+apatite), 2) “megacrysts” of clinopyroxene and K-feldspar, both with inclusions of clinopyroxene, biotite and apatite. Megacrysts of alkali-rich feldspar associated with corundum and HFSE-bearing minerals, and composite xenoliths formed of pyroxenite and K-feldspar-rich lithology have also been described from this locality (Menzies et al., 1986, Geol. Soc. Australia Spec. Pub.; Upton et al., 2009, Mineral. Mag.).</p><p>We interpret the “xenoliths” as products of crystallization of fractionated mafic melt(s). The primary character of Sr isotopic ratios in plagioclase (<sup>87</sup>Sr/<sup>86</sup>Sr <0.702) suggests that parental melt of those lithologies originated from melting of depleted lithospheric mantle sources. The “megacrysts” represent fragments of disintegrated alkaline pegmatite(s) formed from melt of plausible mantle origin, possibly enriched (<sup>87</sup>Sr/<sup>86</sup>Sr in feldspar >0.704).</p><p>Trace element composition, similar Sr isotopic ratios of minerals and textural features of “xenoliths” and “megacrysts” groups suggest their close genetic relationship. This geochemical resemblance may reflect crystallisation from primarily similar melt(s) and source regions affected by similar metasomatism. Petrographic features observed in rocks described by Upton et al., (2009) imply that the parental magma of megacrysts might have intruded the rocks forming the xenoliths group. Moreover, the Rb-Sr ages of xenoliths (Der-Chuen et al., 1993, GCA) indicate crystallisation during (or shortly after) Caledonian orogeny. Preliminary age relationship between groups will be determined by on-going Rb-Sr dating of megacrysts.</p><p>Xenoliths similar to diorites from Loch Roag were reported by Badenszki et al. (2019, JoP) from the Midland Valley terrane (“metadiorites” of protolith ages ca. 415 Ma). They were interpreted as products of alkaline syn-/post-collisional Caledonian magmatism. Our study shows that non-peridotitic xenoliths from Loch Roag dyke might represent a record of similar (or the same) magmatism in the northernmost, “Laurentian” part of Scotland. This study presents the first report of such Caledonian magmatism record within the Hebridean Terrane.</p><p>Founded by Polish National Science Centre grant no. UMO-2016/23/B/ST10/01905, part of the data was obtained thanks to the Polish-Austrian project no. WTZ PL 08/2018.</p>

Sign in / Sign up

Export Citation Format

Share Document