Elemental abundances relevant to identification of magma sources

1984 ◽  
Vol 310 (1514) ◽  
pp. 535-547 ◽  
Keyword(s):  
Trace Element ◽  
Mantle Peridotite ◽  
Oceanic Island ◽  
Chemical Characteristics ◽  
Island Arcs ◽  
Oceanic Ridge ◽  
Aleutian Arc ◽  
Isotopic Evolution ◽  
Magma Sources ◽  
Back Arc

The search for chemical characteristics of magma sources is usually done by analysing the magmas themselves. This indirect approach has limitations: clearly the magma has only some of the source’s characteristics. What we require are process-independent chemical characteristics, analogous to the isotopic abundance of radiogenic daughter isotopes that have been used so successfully in defining magma sources. Process-independent chemical characteristics in mid-oceanic ridge, oceanic island and island-arc basalts (m.o.r.b., o.i.b., i.a.b.) have been used to identify contrasting chemical characteristics of mantle peridotite from these three tectonically distinct regions. As an example, the abundance ratios of one group of elements (e.g. Cs, K, Rb, Ba, U, and perhaps Th) relative to another group (e.g. light r.e.e., Zr, Hf) are found to be fractionation-independent during most shallow-level basalt fractionation. These ratios are presumed to reflect the chemical characteristics of the mantle source of basalt from the three tectonic environments. In particular the ratios indicate the large cation-depleted nature of all m.o.r.b. and most o.i.b. peridotite sources. In common with many other island arcs, the abundance ratios are consistently higher in mantle under the Aleutian arc than in adjacent non-arc mantle represented by oceanic ridge, oceanic island, and back-arc basalts. The contention that subduction of sediment could result in arc mantle sources with these high ratios is substantiated by trace element analyses of Ba and Cs-rich deep sea sediments of the type that are being subducted at present at the Aleutian trench. The importance of recycling of sediment into the mantle at island arcs as an important control on the trace element (and isotopic) evolution of the mantle is indicated.

Geochemical evidence for the emplacement of the Whin Sill complex of northern England

1985 ◽  
Vol 122 (4) ◽  
pp. 389-396 ◽  
Author(s):  
R. S. Thorpe ◽  
R. Macdonald
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Partial Melting ◽  
Sedimentary Rocks ◽  
Crustal Contamination ◽  
Mantle Peridotite ◽  
Chemical Characteristics ◽  
Heterogeneous Mantle ◽  
Magma Pulses ◽  
Significant Chemical

AbstractThe Whin Sill comprises a major quartz tholeiite sill of late Carboniferous age underlying an area of c. 5000 km2 and with a volume of c. 200 km3, associated with contemporaneous dykes emplaced within Carboniferous sedimentary rocks in northeast England. New trace element analyses of chilled margins, sill interiors and dykes indicate that the Whin Sill complex magmas show significant chemical variations in terms of the relatively stable trace elements Th, Ce, Y, Zr, Nb and Ni. These data indicate that the complex was fed by a large number of compositionally distinct magma pulses, and that certain of the dykes may have formed feeder channels for the sill. The chemical characteristics of the sill and dyke samples are consistent with derivation by extensive polybaric fractional crystallization of olivine tholeiite magma derived by partial melting of compositionally heterogeneous mantle peridotite and/or crustal contamination of mantle-derived magmas.

Archean Rocks of Shoshonitic Affinities at Bijou Point, Northwestern Ontario

1974 ◽  
Vol 11 (10) ◽  
pp. 1407-1413 ◽  
Author(s):  
T. E. Smith ◽  
F. J. Longstaffe
Keyword(s):  
Trace Element ◽  
Chemical Characteristics ◽  
Island Arcs ◽  
Northwestern Ontario ◽  
Intrusive Rocks ◽  
Trace Element Contents ◽  
Greenstone Belts ◽  
Northwest Ontario ◽  
Late Stages ◽  
Shoshonitic Series

The Archean volcanic and intrusive rocks of Bijou Point, northwest Ontario show several chemical characteristics which suggest affinities to the alkali or shoshonitic series characteristic of late stages of evolution in modern island arcs. The rocks have unusually high total alkalis (7% at 58–65% SiO2), high Al2O3 and high trace element contents (Ba 800–2500 ppm, Rb 50–350 ppm, Sr 600–2000 ppm). The presence of such rocks in the greenstone belts of the Superior Province serves to further emphasize the similarities between these ancient volcanics and their modern counterparts.

scholarly journals Correction to: Isotopic evolution of prehistoric magma sources of Mt. Etna, Sicily: Insights from the Valle Del Bove

2021 ◽  
Vol 176 (9) ◽  
Author(s):  
P. D. Kempton ◽  
A. Spence ◽  
H. Downes ◽  
J. Blichert-Toft ◽  
J. G. Bryce ◽  
...  
Keyword(s):  
Isotopic Evolution ◽  
Magma Sources ◽  
Mt Etna

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.

Geochemistry and geochronology of OIB-type, Early Jurassic magmatism in the Zhangguangcai range, NE China, as a result of continental back-arc extension

2018 ◽  
Vol 158 (1) ◽  
pp. 143-157 ◽  
Author(s):  
Guangying Feng ◽  
Yildirim Dilek ◽  
Xiaolu Niu ◽  
Fei Liu ◽  
Jingsui Yang
Keyword(s):  
East Asia ◽  
Trace Element ◽  
Partial Melting ◽  
Early Jurassic ◽  
Ne China ◽  
Mafic Rocks ◽  
Asthenospheric Mantle ◽  
Trace Element Contents ◽  
Pacific Slab ◽  
Back Arc

AbstractThe Zhangguangcai Range in the Xing’an Mongolian Orogenic Belt, NE China, contains Early Jurassic (c. 188 Ma) Dabaizigou (DBZG) porphyritic dolerite. Compared with other island-arc mafic rocks, the DBZG dolerite is characterized by high trace-element contents, relatively weak Nb and Ta enrichments, and no Zr, Hf or Ti depletions, similar to OIB-type rocks. Analysed rocks have (87Sr/86Sr)i ratios of 0.7033–0.7044, relatively uniform positive ɛNd(t) values of 2.3–3.2 and positive ɛHf(t) values of 8.5–17.1. Trace-element and isotopic modelling indicates that the DBZG mafic rocks were generated by partial melting of asthenospheric mantle under garnet- to spinel-facies conditions. The occurrence of OIB-like mafic intrusion suggests significant upwelling of the asthenosphere in response to lithospheric attenuation caused by continental rifting. These processes occurred in an incipient continental back-arc environment in the upper plate of a palaeo-Pacific slab subducting W–NW beneath East Asia.

Subduction-related magmatic imprint of most Philippine ophiolites: implications on the early geodynamic evolution of the Philippine archipelago

2004 ◽  
Vol 175 (5) ◽  
pp. 443-460 ◽  
Author(s):  
Rodolfo A. Tamayo* ◽  
René C. Maury* ◽  
Graciano P. Yumul ◽  
Mireille Polvé ◽  
Joseph Cotten ◽  
...  
Keyword(s):  
Partial Melting ◽  
Subduction Zone ◽  
Volcanic Rocks ◽  
The Philippines ◽  
Island Arc ◽  
Island Arcs ◽  
Geodynamic Evolution ◽  
Wide Range ◽  
Opening And Closing ◽  
Back Arc

Abstract The basement complexes of the Philippine archipelago include at least 20 ophiolites and ophiolitic complexes. These complexes are characterised by volcanic sequences displaying geochemical compositions similar to those observed in MORB, transitional MORB-island arc tholeiites and arc volcanic rocks originating from modern Pacific-type oceans, back-arc basins and island arcs. Ocean island basalt-like rocks are rarely encountered in the volcanic sequences. The gabbros from the ophiolites contain clinopyroxenes and plagioclases showing a wide range of XMg and An values, respectively. Some of these gabbros exhibit mineral chemistries suggesting their derivation from basaltic liquids formed from mantle sources that underwent either high degrees of partial melting or several partial melting episodes. Moreover, some of the gabbros display a crystallization sequence where orthopyroxene and clinopyroxene appeared before plagioclase. The major element compositions of coexisting orthopyroxenes and olivines from the mantle peridotites are consistent with low to high degrees of partial melting. Accessory spinels in these peridotites display a wide range of XCr values as well with some of them above the empirical upper limit of 0.6 often observed in most modern mid-oceanic ridge (MOR) mantle rocks. Co-existing olivines and spinels from the peridotites also exhibit compositions suggesting that they lastly equilibrated under oxidizing mantle conditions. The juxtaposition of volcanic rocks showing affinities with modern MOR and island arc environments suggests that most of the volcanic sequences in Philippine ophiolites formed in subduction-related geodynamic settings. Similarly, their associated gabbros and peridotites display mineralogical characteristics and mineral chemistries consistent with their derivation from modern supra-subduction zone-like environments. Alternatively, these rocks could have, in part, evolved in a supra-subduction zone even though they originated from a MOR-like setting. A simplified scenario regarding the early geodynamic evolution of the Philippines is proposed on the basis of the geochemical signatures of the ophiolites, their ages of formation and the ages and origins of the oceanic basins actually bounding the archipelago, including basins presumed to be now totally consumed. This scenario envisages the early development of the archipelago to be largely dominated by the opening and closing of oceanic basins. Fragments of these basins provided the substratum on top of which the Cretaceous to Recent volcanic arcs of the Philippines were emplaced.

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.

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