Asthenospheric and lower-lithospheric mantle contributions to continental extensional magmatism: An example from the British Tertiary Province

Thompson, R. N.; Morrison, M. A.

doi:10.1016/0009-2541(88)90082-4

Cited by 219 publications

(90 citation statements)

References 53 publications

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“…Both magmatisms plot between the extreme OIB and E-MORB poles, having the post-Triassic magmatism more similitude with the OIB end-member. On the other hand (La/Nb) < 1.5 for both magmatism is indicative of an asthenospheric source (Thompson and Morrison, 1988), but higher La/Nb ratios in the Triassic magmatism could indicate a lithospheric (mantellic?, crustal?) component.…”

Section: Discussionmentioning

confidence: 99%

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Morata¹,

Puga²,

Demant³

et al. 1997

Estud. geol.

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Mesozoic basic magmatism in the External Zones of the Betic Cordilleras (S. Spain) is represented by small tectonic bodies (ophites) in Triassic formations, and submarine flows with abundant pillow-Iavas interbedded with Jurassic sediments. Both basic igneous manifestations suffered very low-to low-grade metamorphism, more intense in the case of the ophites.Two types of ophites are distinguished on the basis of their primary mineralogy. In the first type, orthopyroxene is present in the less differentiated products. Clinopyroxene and Ca-plagioclase are the main primary phases and quartz appears in the more evolved rocks. In the second type, olivine is present in the less differentiated products. Ti-rich augite and Ca-plagioclase are also important primary minerals, but quartz is absent.Whole-rock chemistry (major and trace elements, including REE) also allows us to discriminate between these two groups. The first group has higher SiO z and lower TiO z , PzOs and lower NazO/KzO ratios than the second. Normative quartz is almost invariably present in this first group, whereas normative nepheline (lower than 5%) is characteristic of the second group. Both groups are Sr, K, Ba, Rb, Th, Nb and Ce enriched with respect to normal MORB, but the first group has higher K, Rb, Ba, Th and lower Nb, Ce contents than the alkaline group. NblY and TiN ratios are also different and show a tholeiitic affinity for the first group and transitional to alkaline for the second. Chondrite-normalised REE patterns in both groups are similar and characterized by LREE enrichment with respect to HREE. LREE/HREE ratios are, however, slightly higher in the transitional to alkaline group.Various discriminant tectonic diagrams indicate a continental intraplate setting for both ophite groups. This magmatism is related to the first extensional period of the Betic Cordilleras, during the Triassic-Jurassic. Geochemical differences between the two groups could evidence different degrees of crustal contamination, and/or different mantle sources. Trace element ratios [(La/Ce)n> 1, La/Nb < 1.5] for both magmatism are indicative of an enriched mantle source. Differences in ThIYb, Zr/Nb, ZrIY and Ba/Zr ratios underline the greater influence of a lithospheric component in the case of the Triassic magmatism.Key wOl"ds: Ophites: Continental intraplate magmatism; Mesozoie; External Zones; Betie Cordilleras. RESUMENEl magmatismo basico mesozoico en las Zonas Externas de las Cordilleras Beticas (S. Espafia) esta representado por pequefios bloques tect6nicos (ofitas) en las formaciones triasicas, y coladas submarinas, con abundantes pillow-Iavas intercaladas en los sedimentos jurasicos. Ambos tipos de manifestaciones fgneas sufrieron transformaciones metam6rficas en condiciones de grado bajo a muy bajo, mas intensas en el caso de las ofitas.Sobre la base de la mineralogfa primaria se han distinguido dos tipos de ofitas. En el primer tipo, aparece ortopiroxeno en los terminos menos diferenciados, siendo los clino- piroxenos y plagioclasas calcicas las pr...

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Section: Discussionmentioning

confidence: 99%

Untitled

Morata¹,

Puga²,

Demant³

et al. 1997

Estud. geol.

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“…Most of the IAB-type gabbroic and basaltic rocks of Chukotka have lower Nb/Ta values (11.3-17.9) than those of primitive mantle (mean value, 17.5), and higher La/Nb (2.6-3.8; i.e., >1.5, Fig. 10) and La/Ta (39.3-57.1; i.e., >30) values than those of basalts derived from asthenospheric mantle (Thompson and Morrison, 1988). However, the OIB-type gabbros have significantly low content of La/ Nb (0.68-0.99) and La/Ta (10.3-14.3) ratios similar to those of basalts derived from unaltered ansthenospheric mantle.…”

Section: Constraints On Mantle Sourcesmentioning

confidence: 91%

Petrogenises of Triassic gabbroic and basaltic rocks from Chukotka, NE Russia: Eastern end of the ‘arc–type’ Siberian LIP?

Desta

Ishiwatari

Machi

et al. 2015

Journal of Mineralogical and Petrological Sciences

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The Triassic gabbroic intrusions and associated basaltic lavas from Chukotka are mainly tholeiitic with both ocean island basalt (OIB) and island arc basalt (IAB)-type geochemical signatures. Mg-number [Mg# = 100 × Mg/(Mg + Fe 2+ )] is around 40 for OIB-type gabbros, ranges from 48 to 66 for IAB-type hornblende-rich gabbros, and 43 to 65 for IAB-type basaltic rocks (ankaramites, lamprophyres, pyroxene-phyric basalts and hornblende-phyric basaltic andesite). TiO 2 contents of the IAB-type gabbros and basaltic rocks are low (<2 wt%), but are high in OIB-type gabbros (4.3-5.3 wt%). OIB-type gabbros are typically enriched in FeO * (16-18 wt%) as compared to IAB-type gabbros (10-14 wt%) and IAB-type lavas (ankaramites,~10 wt%; lamprophyres,~14; pyroxene-phyric basalt, 11 wt% and basaltic andesite, 9-10 wt. %). In the primitive mantle normalized trace element patterns, IAB-type basalts and gabbros are characterized by depletion in HFSE (Nb, Ta, Zr and Hf ) and enrichment in LILE. OIB-type gabbros can be distinguished from the rests by the absence of HFSE depletion, with strong negative Sr anomaly. The positive Ti anomaly in the OIB-type gabbros can be attributed to high content of ilmenite in these rocks. Trace element characteristics of IAB-type gabbroic rocks and basalts are compatible with their magmas derived from subduction influenced melts, whereas OIB-type gabbros show within-plate geochemical characteristics. IAB-type gabbros and basaltic rocks display similar geochemical features to the low-Ti Nadezhdinsky suit (Noril'sk region) and Bel'kov dolerite (New Siberian Islands) of the Siberian large igneous province (LIP) in view of HFSE depletion and high H 2 O content of the magma to crystallize abundant hornblende not only in gabbros but also as phenocrysts in basalts. The Triassic gabbroic and basaltic rocks of both OIB and IAB types may as a whole represents the eastern end of the Siberian LIP.

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“…The dykes have relatively high La/Nb (1.78-3.29), La/Ta (23.9-45.0) and Zr/Nb (7.8-28.0) ratios. These values suggest that SCLM source region has been influenced by hydrous metasomatism [23][24][25][26] . In Ce/Pb versus La/Nb diagram 23 ( Figure 6 e), the dykes are plotted on subduction-related (influenced by metasomatism) or lithospheric mantle origin field.…”

Section: Eastern Belt Of Peninsular Malaysiamentioning

confidence: 91%

Petrogenesis of Ajil Mafic Dykes from Eastern Belt of Peninsular Malaysia:Fractionated within Plate Lithospheric Mantle Magma Beneath the Eastern Malaya Block

Badruldin¹,

Ghani²,

Quek³

2017

Current Science

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North-eastern trending mafic dykes are found intruding granitic body in Ajil area, Eastern Belt of Peninsular Malaysia. The intrusions display sharp, vertical to sub-vertical contacts to granitic host and consist mainly of plagioclase and clinopyroxene. Majority of the dykes are quartz tholeiite with some olivine tholeiite. All dykes display enrichment in light rare earth elements (LREE) relative to heavy rare earth elements (HREE) and depletion in high field strength elements (HFSE) and Pb. Low compatible elements' content such as MgO, Ni and Cr implied that crystal fractionation were controlled by olivine and clinopyroxene. The dykes were originated from shallow lithospheric mantle, the source region of which has been influenced by hydrous metasomatism. The emplacement of the dykes took place in fault-controlled within-plate tectonic setting.

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Asthenospheric and lower-lithospheric mantle contributions to continental extensional magmatism: An example from the British Tertiary Province

Cited by 219 publications

References 53 publications

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Petrogenises of Triassic gabbroic and basaltic rocks from Chukotka, NE Russia: Eastern end of the ‘arc–type’ Siberian LIP?

Petrogenesis of Ajil Mafic Dykes from Eastern Belt of Peninsular Malaysia:Fractionated within Plate Lithospheric Mantle Magma Beneath the Eastern Malaya Block

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