Petrology of Basanitic Lavas of the Daur–Hentiyn Range (P–T Conditions of Formation, Crystallization Sequence, and Sources of Material)

2021 ◽  
Vol 62 (03) ◽  
pp. 291-305
Author(s):  
A.Ya. Medvedev ◽  
E.I. Demonterova ◽  
A.A. Karimov ◽  
V.A. Belyaev
Keyword(s):  
Electron Probe ◽  
Volcanic Rocks ◽  
Oceanic Island ◽  
Volcanic Area ◽  
Crystallization Sequence ◽  
Nd Isotope ◽  
Mineral Compositions ◽  
Oceanic Island Basalts ◽  
South Baikal ◽  
Comprehensive Study

Abstract —We performed a comprehensive study of basanites from the Daur–Hentiyn Range and present the first data on their Sr and Nd isotope and mineral compositions (electron probe microanalysis). The study has shown that the basanites are chemically similar to the volcanic rocks of the South Baikal volcanic area (SBVA) and are slightly different from oceanic island basalts in higher contents of Ba, Th, La, and Sr. The crystallization temperatures and pressures for the Fo0.85 olivine–melt equilibrium have been estimated, 1186–1137 ºC, 1.09–1.06 GPa, and the sequence of mineral crystallization has been established. The obtained Sr and Nd isotope data indicate that the basanitic magmas were generated from material with PREMA and EMI isotope parameters.

Le terrane de Slide Mountain (Cordillères canadiennes) : une lithosphère océanique marquée par des points chauds

2003 ◽  
Vol 40 (6) ◽  
pp. 833-852 ◽  
Author(s):  
M Tardy ◽  
H Lapierre ◽  
D Bosch ◽  
A Cadoux ◽  
A Narros ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Oceanic Island ◽  
Light Rare Earth ◽  
Isotopic Compositions ◽  
Incompatible Elements ◽  
Depleted Mantle ◽  
Mantle Sources ◽  
British Colombia ◽  
Ultramafic Cumulates ◽  
Back Arc

The Slide Mountain Terrane consists of Devonian to Permian siliceous and detrital sediments in which are interbedded basalts and dolerites. Locally, ultramafic cumulates intrude these sediments. The Slide Mountain Terrane is considered to represent a back-arc basin related to the Quesnellia Paleozoic arc-terrane. However, the Slide Mountain mafic volcanic rocks exposed in central British Colombia do not exhibit features of back-arc basin basalts (BABB) but those of mid-oceanic ridge (MORB) and oceanic island (OIB) basalts. The N-MORB-type volcanic rocks are characterized by light rare-earth element (LREE)-depleted patterns, La/Nb ratios ranging between 1 and 2. Moreover, their Nd and Pb isotopic compositions suggest that they derived from a depleted mantle source. The within-plate basalts differ from those of MORB affinity by LREE-enriched patterns; higher TiO2, Nb, Ta, and Th abundances; lower εNd values; and correlatively higher isotopic Pb ratios. The Nd and Pb isotopic compositions of the ultramafic cumulates are similar to those of MORB-type volcanic rocks. The correlations between εNd and incompatible elements suggest that part of the Slide Mountain volcanic rocks derive from the mixing of two mantle sources: a depleted N-MORB type and an enriched OIB type. This indicates that some volcanic rocks of the Slide Mountain basin likely developed from a ridge-centered or near-ridge hotspot. The activity of this hotspot is probably related to the worldwide important mantle plume activity that occurred at the end of Permian times, notably in Siberia.

Lower Palaeozoic and Precambrian igneous rocks from eastern England, and their bearing on late Ordovician closure of the Tornquist Sea: constraints from U-Pb and Nd isotopes

1993 ◽  
Vol 130 (6) ◽  
pp. 835-846 ◽  
Author(s):  
S. R. Noble ◽  
R. D. Tucker ◽  
T. C. Pharaoh
Keyword(s):  
Volcanic Rocks ◽  
Igneous Rocks ◽  
Calc Alkaline ◽  
Nd Isotopes ◽  
Nd Isotope ◽  
Magmatic Arc ◽  
The North ◽  
Basement Rocks ◽  
Continental Arc ◽  
Lower Palaeozoic

AbstractThe U-Pb isotope ages and Nd isotope characteristics of asuite of igneous rocks from the basement of eastern England show that Ordovician calc-alkaline igneous rocks are tectonically interleaved with late Precambrian volcanic rocks distinct from Precambrian rocks exposed in southern Britain. New U-Pb ages for the North Creake tuff (zircon, 449±13 Ma), Moorby Microgranite (zircon, 457 ± 20 Ma), and the Nuneaton lamprophyre (zircon and baddeleyite, 442 ± 3 Ma) confirm the presence ofan Ordovician magmatic arc. Tectonically interleaved Precambrian volcanic rocks within this arc are verified by new U-Pb zircon ages for tuffs at Glinton (612 ± 21 Ma) and Orton (616 ± 6 Ma). Initial εNd values for these basement rocks range from +4 to - 6, consistent with generation of both c. 615 Ma and c. 450 Ma groups of rocksin continental arc settings. The U-Pb and Sm-Nd isotope data support arguments for an Ordovician fold/thrust belt extending from England to Belgium, and that the Ordovician calc-alkaline rocks formed in response to subductionof Tornquist Sea oceanic crust beneath Avalonia.

Early Tertiary basalts from the Labrador Sea floor and Davis Strait region

1989 ◽  
Vol 26 (5) ◽  
pp. 956-968 ◽  
Author(s):  
D. B. Clarke ◽  
B. I. Cameron ◽  
G. K. Muecke ◽  
J. L. Bates
Keyword(s):  
Volcanic Rocks ◽  
Labrador Sea ◽  
Baffin Island ◽  
Nd Isotope ◽  
Sea Floor ◽  
West Greenland ◽  
Depleted Mantle ◽  
Davis Strait ◽  
Isotope Systematics ◽  
Seawater Exchange

Fine- to medium-grained, phyric and aphyric basalt samples from ODP Leg 105, site 647A, in the Labrador Sea show little evidence of alteration. Chemically, these rocks are low-potassium (0.01–0.09 wt.% K2O), olivine- to quartz-normative tholeiites that compare closely with the very depleted terrestrial Paleocene volcanic rocks in the Davis Strait region of Baffin Island and West Greenland. However, differences exist in the Sr–Nd isotope systematics of the two suites; the Labrador Sea samples have ε Nd values (+9.3) indicative of a more depleted source, and are higher in 87Sr/86Sr (0.7040), relative to the Davis Strait basalts (ε Nd +2.54 to +8.97; mean 87Sr/86Sr 0.7034). The higher 87Sr/86Sr in the Labrador Sea samples may reflect seawater exchange despite no petrographic evidence for significant alteration. The Labrador Sea and early Davis Strait basalts may have been derived from a similar depleted mantle source composition; however, the later Davis Strait magmas were generated from a different mantle. None of the Baffin Island, West Greenland, or Labrador Sea samples show unequivocal geochemical evidence for contamination with continental crust.

A 5-km-thick reservoir with >380,000 km3 of magma within the ancient Earth's crust

2021 ◽  
Author(s):  
Rais Latypov ◽  
Sofya Chistyakova ◽  
Richard Hornsey ◽  
Gelu Costin ◽  
Mauritz van der Merwe
Keyword(s):  
Bushveld Complex ◽  
Earth’S Crust ◽  
Magma Chambers ◽  
Crystallization Sequence ◽  
Igneous Provinces ◽  
Research Concept ◽  
History Of ◽  
Mineral Compositions ◽  
Earth's Crust ◽  
Chamber Floor

Abstract Several recent studies have argued that large, long-lived and molten magma chambers1–10 may not occur in the shallow Earth’s crust11–23. Here we present, however, field-based observations from the Bushveld Complex24 that provide evidence to the contrary. In the eastern part of the complex, the magmatic layering was found to continuously drape across a ~4-km-high sloping step in the chamber floor. Such deposition of magmatic layering implies that the resident melt column was thicker than the stepped relief of the chamber floor. Prolonged internal differentiation within such a thick magma column is further supported by evolutionary trends in crystallization sequence and mineral compositions through the sequence. The resident melt column in the Bushveld chamber during this period is estimated to be >5-km-high in thickness and >380,000 km3 in volume. This amount of magma is three orders of magnitude larger than any known super-eruptions in the Earth’s history25 and is only comparable to the extrusive volumes of some of Earth’s large igneous provinces26. This suggests that super-large, entirely molten and long-lived magma chambers, at least occasionally, occur in the geological history of our planet. Therefore, the classical view of magma chambers as ‘big magma tanks’1–10 remains a viable research concept for some of Earth’s magmatic provinces.

Rare earth element, Sr- and Nd-isotope evidence for petrogenesis of Permian basaltic and K-rich volcanic rocks from south-west England

1986 ◽  
Vol 50 (357) ◽  
pp. 481-489 ◽  
Author(s):  
R. S. Thorpe ◽  
M. E. Cosgrove ◽  
P. W. C. van Calsteren
Keyword(s):  
High Field ◽  
Earth Element ◽  
Volcanic Rocks ◽  
Transition Element ◽  
Oceanic Lithosphere ◽  
High Field Strength ◽  
Nd Isotope ◽  
South West ◽  
Isotope Evidence ◽  
South West England

AbstractPermian basic/ultrabasic lavas from south-west England may be divided into a ‘basaltic’ and a K-rich group. Both groups have enrichment of large-ion lithophile (LIL) elements relative to high field strength (HFS) elements, and the K-rich group show large degrees of LIL enrichment (c.50–500 times primordial mantle) in association with varied transition element concentrations. Samples from both groups 87Sr/86Sri = 0.704–0.705 and 143Nd/144Ndi = 0.5123–0.5127 and plot close to the mantle array on an ɛSr−ɛNd diagram. These data are interpreted in terms of derivation of the lavas from magmas resulting from partial melting of mantle which had experienced less (for the basaltic group) or more (for the K-rich group) enrichment in LIL elements as a result of migration of mantle melts. Such enrichment accompanied or followed subduction of oceanic lithosphere below south-west England. The resultant magmas experienced fractional crystallization of olivine and pyroxene prior to eruption.

Lithogeochemistry of volcano-plutonic assemblages of the southern Hanson Lake Block and southeastern Glennie Domain, Trans-Hudson Orogen: evidence for a single island arc complex

1999 ◽  
Vol 36 (2) ◽  
pp. 209-225 ◽  
Author(s):  
Ralf O Maxeiner ◽  
Tom II Sibbald ◽  
William L Slimmon ◽  
Larry M Heaman ◽  
Brian R Watters
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Oceanic Island ◽  
Island Arc ◽  
Island Arcs ◽  
Calc Alkaline ◽  
East Central ◽  
South Central ◽  
Volcaniclastic Rocks ◽  
Flin Flon

This paper describes the geology, geochemistry, and age of two amphibolite facies volcano-plutonic assemblages in the southern Hanson Lake Block and southeastern Glennie Domain of the Paleoproterozoic Trans-Hudson Orogen of east-central Saskatchewan. The Hanson Lake assemblage comprises a mixed suite of subaqueous to subaerial dacitic to rhyolitic (ca. 1875 Ma) and intercalated minor mafic volcanic rocks, overlain by greywackes. Similarly with modern oceanic island arcs, the Hanson Lake assemblage shows evolution from primitive arc tholeiites to evolved calc-alkaline arc rocks. It is intruded by younger subvolcanic alkaline porphyries (ca. 1861 Ma), synvolcanic granitic plutons (ca. 1873 Ma), and the younger Hanson Lake Pluton (ca. 1844 Ma). Rocks of the Northern Lights assemblage are stratigraphically equivalent to the lower portion of the Hanson Lake assemblage and comprise tholeiitic arc pillowed mafic flows and felsic to intermediate volcaniclastic rocks and greywackes, which can be traced as far west as Wapawekka Lake in the south-central part of the Glennie Domain. The Hanson Lake volcanic belt, comprising the Northern Lights and Hanson Lake assemblages, shows strong lithological, geochemical, and geochronological similarities to lithotectonic assemblages of the Flin Flon Domain (Amisk Collage), suggesting that all of these areas may have been part of a more or less continuous island arc complex, extending from Snow Lake to Flin Flon, across the Sturgeon-Weir shear zone into the Hanson Lake Block and across the Tabbernor fault zone into the Glennie Domain.

Frequency spectrum of the electrical properties of seawater-saturated ocean crust and oceanic island basalts

1978 ◽  
Vol 15 (9) ◽  
pp. 1489-1495 ◽  
Author(s):  
M. J. Drury
Keyword(s):  
Electrical Properties ◽  
Frequency Spectrum ◽  
Conduction Mechanism ◽  
Oceanic Island ◽  
Pore Fluid ◽  
Membrane Polarization ◽  
Conduction Mechanisms ◽  
Metallic Mineral ◽  
Dominant Conduction Mechanism ◽  
Oceanic Island Basalts

The frequency spectrum of electrical properties of seawater-saturated oceanic crust and oceanic island basalts has been studied. All samples showed at least two of three possible polarization mechanisms: dielectric, membrane, and electrode. The membrane polarization appears to result from the presence of clay minerals, which frequently line or block pores and cracks in the samples. The dominant conduction mechanism in the samples is pore fluid (seawater) conduction, but the electrical properties of samples containing clay are modified by the clay. The results support the suggestion by Drury that a model of three conduction mechanisms acting approximately in parallel—pore fluid, clay mineral, and metallic mineral conduction—describes the electrical properties of seawater-saturated basalts.

The Mamonia Complex (SW Cyprus) revisited: remnant of Late Triassic intra-oceanic volcanism along the Tethyan southwestern passive margin

2006 ◽  
Vol 144 (1) ◽  
pp. 1-19 ◽  
Author(s):  
H. LAPIERRE ◽  
D. BOSCH ◽  
A. NARROS ◽  
G. H. MASCLE ◽  
M. TARDY ◽  
...  
Keyword(s):  
Partial Melting ◽  
Oceanic Crust ◽  
Volcanic Rocks ◽  
Upper Triassic ◽  
Oceanic Island ◽  
Alkali Basalts ◽  
Enriched Mantle ◽  
Type 3

Upper Triassic volcanic and sedimentary rocks of the Mamonia Complex in southwestern Cyprus are exposed in erosional windows through the post-Cretaceous cover, where the Mamonia Complex is tectonically imbricated with the Troodos and Akamas ophiolitic suites. Most of these Upper Triassic volcanic rocks have been considered to represent remnants of Triassic oceanic crust and its associated seamounts. New Nd and Pb isotopic data show that the whole Mamonia volcanic suite exhibits features of oceanic island basalts (OIB). Four rock types have been distinguished on the basis of the petrology and chemistry of the rocks. Volcanism began with the eruption of depleted olivine tholeiites (Type 1) and oceanic island tholeiites (Type 2) associated with deep basin siliceous and/or calcareous sediments. The tholeiites were followed by highly phyric alkali basalts (Type 3) interbedded with pelagic Halobia-bearing limestones or white reefal limestones. Strongly LREE-enriched trachytes (Type 4) were emplaced during the final stage of volcanic activity. Nd and Pb isotopic ratios suggest that tholeiites and mildly alkali basalts derived from partial melting of heterogeneous enriched mantle sources. Fractional crystallization alone cannot account for the derivation of trachytes from alkaline basalts. The trachytes could have been derived from the partial melting at depth of mafic material which shares with the alkali basalts similar trace element and isotopic compositions. This is corroborated by the rather similar isotopic compositions of the alkali basalts and trachytes. The correlations observed between incompatible elements (Nb, Th) and εNd and Pb isotopic initial ratios suggest that the Mamonia suite was derived from the mixing of a depleted mantle (DMM) and an enriched component of High μ (μ = 238U/204Pb, HIMU) type. Models using both Nd and Pb isotopic initial ratios suggest that the depleted tholeiites (Type 1) derived from a DMM source contaminated by an Enriched Mantle Type 2 component (EM2), and that the oceanic tholeiites (Type 2), alkali basalts (Type 3) and trachytes (Type 4) were derived from the mixing of the enriched mantle source of the depleted tholeiites with a HIMU component. None of the Mamonia volcanic rocks show evidence of crustal contamination. The Upper Triassic within-plate volcanism likely erupted in a small southerly Neotethyan basin, located north of the Eratosthenes seamount and likely floored by oceanic crust.

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