Geochemistry of late Caledonian minettes from Northern Britain: implications for the Caledonian sub-continental lithospheric mantle

1996 ◽  
Vol 60 (398) ◽  
pp. 221-236 ◽  
Author(s):  
Jason C. Canning ◽  
P. J. Henney ◽  
M. A. Morrison ◽  
J. W. Gaskarth
Keyword(s):  
Trace Elements ◽  
Partial Melting ◽  
Fractional Crystallization ◽  
Lithospheric Mantle ◽  
Sr Isotope ◽  
Crustal Assimilation ◽  
Continental Lithospheric Mantle ◽  
Compositional Changes ◽  
Tectonic Dislocations

AbstractThe geochemistry of late Caledonian minettes from across the orogenic belt is compared in order to constrain the composition of the Caledonian sub-continental lithospheric mantle (SCLM). All the minettes are similar petrographically and chemically and several samples have characteristics typical of near primary mantle melts. Samples from the Northern Highlands and the Caledonian foreland show enrichment in many trace elements (notably LILE and LREE) relative to those from the Grampians, the Southern Uplands and northern England, coupled with distinct Nd and Sr isotope characteristics. Processes such as fractional crystallization, crustal assimilation, and partial melting played a negligible role in creating the differences between the two groups which reflect long-term, time-integrated differences in the compositions of their SCLM sources. The Great Glen Fault appears to represent the boundary between these two lithospheric mantle domains. Other currently exposed Caledonian tectonic dislocations cannot be correlated directly with compositional changes within the SCLM. The chemical provinciality displayed by the minettes shows some resemblance to that within other late Caledonian igneous suites, including the newer granites, suggesting that the minettes may represent the lithospheric mantle contributions to these rocks.

scholarly journals Geochemical behaviour of trace elements during fractional crystallization and crustal assimilation of the felsic alkaline magmas of the state of Rio de Janeiro, Brazil

2015 ◽  
Vol 87 (4) ◽  
pp. 1959-1979 ◽  
Author(s):  
AKIHISA MOTOKI ◽  
SUSANNA E. SICHEL ◽  
THAIS VARGAS ◽  
DEAN P. MELO ◽  
KENJI F. MOTOKI
Keyword(s):  
Trace Elements ◽  
Continental Crust ◽  
Fractional Crystallization ◽  
Rio De Janeiro ◽  
Nepheline Syenite ◽  
The State ◽  
Granitic Rocks ◽  
Alkaline Basalt ◽  
Crustal Assimilation ◽  
Geochemical Behaviour

ABSTRACT This paper presents geochemical behaviour of trace elements of the felsic alkaline rocks of the state of Rio de Janeiro, Brazil, with special attention of fractional crystallization and continental crust assimilation. Fractionation of leucite and K-feldspar increases Rb/K and decreases K2O/(K2O+Na2O). Primitive nepheline syenite magmas have low Zr/TiO2, Sr, and Ba. On the Nb/Y vs. Zr/TiO2 diagram, these rocks are projected on the field of alkaline basalt, basanite, and nephelinite, instead of phonolite. Well-fractionated peralkaline nepheline syenite has high Zr/TiO2 but there are no zircon. The diagrams of silica saturation index (SSI) distinguish the trends originated form fractional crystallization and crustal assimilation. In the field of SSI<-200, Zr/TiO2 and Ba/Sr have negative correlations to SSI in consequence of fractional crystallization. In the field of SSI>-200, they show positive correlations due to continental crust assimilation. Total REEs (Rare Earth Elements) is nearly 10 times that of granitic rocks, but LaN/SmN and LaN/YbN are similar. REE trend is linear and Eu anomaly is irrelevant. The pegmatitic liquid generated by country rock partial melting is SiO2-oversaturated and peraluminous with high Ba, Sr, Ba/Sr, Zr/TiO2, and SSI, with high content of fluids. This model justifies the peraluminous and SiO2-oversaturated composition of the rocks with relevant effects of continental crust assimilation.

scholarly journals An Overview of the Geochemical Characteristics of Oceanic Carbonatites: New Insights from Fuerteventura Carbonatites (Canary Islands)

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 203
Author(s):  
Gabriele Carnevale ◽  
Antonio Caracausi ◽  
Alessandra Correale ◽  
Laura Italiano ◽  
Silvio G. Rotolo
Keyword(s):  
Trace Elements ◽  
Canary Islands ◽  
Lithospheric Mantle ◽  
Noble Gases ◽  
Cape Verde ◽  
Geochemical Characteristics ◽  
Isotopic Ratios ◽  
Isotopic Study ◽  
Continental Lithospheric Mantle

The occurrence of carbonatites in oceanic settings is very rare if compared with their continental counterpart, having been reported only in Cape Verde and Canary Islands. This paper provides an overview of the main geochemical characteristics of oceanic carbonatites, around which many debates still exist regarding their petrogenesis. We present new data on trace elements in minerals and whole-rock, together with the first noble gases isotopic study (He, Ne, Ar) in apatite, calcite, and clinopyroxene from Fuerteventura carbonatites (Canary Islands). Trace elements show a similar trend as Cape Verde carbonatites, almost tracing the same patterns on multi-element and REE abundance diagrams. 3He/4He isotopic ratios of Fuerteventura carbonatites reflect a shallow (sub-continental lithospheric mantle, SCLM) He signature in their petrogenesis, and they clearly differ from Cape Verde carbonatites, i.e., fluids from a deep and low degassed mantle with a primitive plume-derived He signature are involved in their petrogenesis.

scholarly journals Petrogenesis of Quaternary Shoshonitic Volcanism in NE Iran (Ardabil): Implication for Postcollisional Magmatism

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Habib Shahbazi Shiran
Keyword(s):  
Trace Elements ◽  
Rare Earth ◽  
Mantle Source ◽  
Lithospheric Mantle ◽  
Volcanic Rocks ◽  
Enriched Mantle ◽  
Low Degree ◽  
Continental Lithospheric Mantle ◽  
Ne Iran ◽  
Postcollisional Magmatism

Trachyandesites, trachytes, andesites, and pyrocalstic rocks, with shoshonitic signature, are the main Quaternary volcanic rocks in the Sabalan region (Ardabil). Plagiocalse, K-feldspar, biotite associated with clinopyroxene, and glass are the main constituents of these lavas. Plagioclases are andesine to labradorite while clinopyroxenes have augitic composition. The Sabalan volcanic rocks show enrichment in LREEs (relative to HREEs) and are characterized by enrichment in LILEs and depletion in HFSEs. Petrological observations, along with rare earth and trace elements geochemistry, suggest shoshonitic signature for Sabalan lavas. This signature highlights derivation from a subduction-related source. The Sabalan volcanic rocks are isotopically characterized by derivation from an enriched mantle source with a tendency to plot in the fields defined by island-arc basalts (IAB) and OIBs (in εNd versus 87Sr/86Sr diagram). The geochemical and isotopic characteristics of the Sabalan lavas suggest that their magma has been issued via low degree partial melting of a subduction-metasomatized continental lithospheric mantle. The formation of these lavas is related to slab steepening and breakoff in a postcollisional regime.

Composite Ordovician lamprophyre (spessartite) intrusions around the Midlands Microcraton in central Britain

1993 ◽  
Vol 130 (5) ◽  
pp. 657-663 ◽  
Author(s):  
R. S. Thorpe ◽  
J. W. Gaskarth ◽  
P. J. Henney
Keyword(s):  
Partial Melting ◽  
Fractional Crystallization ◽  
Mantle Source ◽  
Lithospheric Mantle ◽  
Sedimentary Rocks ◽  
Small Degree ◽  
Chemical Characteristics ◽  
Lower Ordovician ◽  
Lower Palaeozoic

AbstractLamprophyre sills and dykes of Ordovician age were emplaced within Cambrian–Lower Ordovician sedimentary rocks around the northern margins of the Midlands Microcraton. The intrusions show internal mineralogical and chemical variations indicating emplacement as multiple intrusions of co-magmatic pulses. The chemical characteristics of the lamprophyre magmas indicate formation by small-degree volatile-rich partial melting of lithospheric mantle enriched and modified by Lower Palaeozoic subduction (Th/Ta 5.3–11.6, La/Ta 29–82.3), together with a contribution from within-plate mantle source (Zr/Yc. 6) and/or mineralogically heterogeneous lithosphere, followed by varying degrees of fractional crystallization during uprise.

From the Finero phlogopite peridotite to the shoshonitic magmatism of the Dolomites: unveiling the evolution of the Sub-Continental Lithospheric Mantle beneath the Southern Alps (Northern Italy)

2021 ◽  
Author(s):  
Federico Casetta ◽  
Massimo Coltorti ◽  
Ryan B. Ickert ◽  
Darren F Mark ◽  
Pier Paolo Giacomoni ◽  
...  
Keyword(s):  
Partial Melting ◽  
Lithospheric Mantle ◽  
Planetary Science ◽  
Southern Alps ◽  
Late Triassic ◽  
Spinel Lherzolite ◽  
Depleted Mantle ◽  
Significant Enrichment ◽  
Continental Lithospheric Mantle ◽  
Ultramafic Cumulates

&lt;p&gt;The Mid-Triassic emplacement of shoshonitic magmas at the NE margin of the Adria plate in concomitance with extensional/transtensional tectonics is one of the most intriguing and peculiar aspects typifying the geodynamic evolution of the Western Tethyan realm. Although often hypothesized, the link between this magmatic event and the metasomatised Southern Alps Sub-Continental Lithospheric Mantle (SCLM) has never been constrained.&lt;/p&gt;&lt;p&gt;Geochemical and petrological analyses of lavas, dykes and ultramafic cumulates belonging to the shoshonitic magmatism of the Dolomites, coupled with pre-existing data on peridotite massifs (i.e. Finero, Balmuccia, Baldissero), were used to reconstruct the evolution of the Southern Alps SCLM between Carboniferous and Triassic. According to our model, a metasomatised amphibole + phlogopite-bearing spinel lherzolite, similar to the Finero phlogopite peridotite and likely generated by interaction between a depleted mantle and slab-derived components during the Variscan subduction, was able to produce magmas with orogenic-like affinity during Mid-Triassic. In this context, partial melting degrees of ca. 5-7% were required for producing primitive SiO&lt;sub&gt;2&lt;/sub&gt;-saturated to -undersaturated melts with shoshonitic affinity (&lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr&lt;sub&gt;i&lt;/sub&gt; = 0.7032-0.7058; &lt;sup&gt;143&lt;/sup&gt;Nd/&lt;sup&gt;144&lt;/sup&gt;Nd&lt;sub&gt;i&lt;/sub&gt; = 0.51219-0.51235; Mg #~ 70; ~1.1 wt% H&lt;sub&gt;2&lt;/sub&gt;O). As testified by the H&lt;sub&gt;2&lt;/sub&gt;O content in mineral phases from the Finero phlogopite peridotite (Tommasi et al., 2017), the modelled Mid-Triassic fertile lithospheric mantle could have been able to preserve a significant enrichment and volatile content (600-800 ppm H&lt;sub&gt;2&lt;/sub&gt;O) for more than 50 Ma, i.e. since the Variscan subduction-related metasomatism. During the Mid-Triassic partial melting event, the modelled Finero-like mantle exhausted the subduction-related signature inherited during the Variscan subduction. Around 20 Ma later, the same lithosphere portion was affected by an asthenospheric upwelling event related to the Late Triassic-Early Jurassic opening of the Alpine Tethys (Casetta et al., 2019).&lt;/p&gt;&lt;p&gt;Casetta, F., Ickert, R.B., Mark, D.F., Bonadiman, C., Giacomoni, P.P., Ntaflos, T., Coltorti, M., 2019. The alkaline lamprophyres of the Dolomitic Area (Southern Alps, Italy): markers of the Late Triassic change from orogenic-like to anorogenic magmatism. Journal of Petrology 60(6), 1263-1298.&lt;/p&gt;&lt;p&gt;Tommasi, A., Langone, A., Padr&amp;#243;n-Navarta, J.A., Zanetti, A., Vauchez, A., 2017. Hydrous melts weaken the mantle, crystallization of pargasite and phlogopite does not: Insights from a petrostructural study of the Finero peridotites, Southern Alps. Earth and Planetary Science Letters 477, 59-72.&lt;/p&gt;

Geochemistry of late Mesozoic lamprophyre dykes from the Taihang Mountains, north China, and implications for the sub-continental lithospheric mantle

2003 ◽  
Vol 140 (1) ◽  
pp. 87-93 ◽  
Author(s):  
B. CHEN ◽  
M. ZHAI
Keyword(s):  
Lithospheric Mantle ◽  
North China ◽  
Parental Magma ◽  
Late Mesozoic ◽  
Isotopic Signatures ◽  
Mantle Enrichment ◽  
Continental Lithospheric Mantle ◽  
Ree Patterns ◽  
Lithospheric Mantle Source

Many late Mesozoic lamprophyre dykes occur in the Taihang Mountains (north China). These lamprophyres are rich in large ion lithophile elements (e.g. Rb, Sr, Ba and K) and light REE, and have highly differentiated REE patterns. They show large but regular variations in chemical and Nd–Sr isotopic compositions. All these suggest that the lamprophyres were produced from differentiation of a parental magma, coupled with contamination by lower crust. The parental magma was derived from melting of a long-term enriched sub-continental lithospheric mantle source as is indicated by the highly enriched isotopic signatures of the lamprophyres. Mantle enrichment in the area was probably produced by interaction of volatile-rich melts released from the asthenosphere with the above lithosphere in middle Proterozoic times.

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