The origin of geochemical diversity of lunar mantle sources inferred from the combined U–Pb, Rb–Sr, and Sm–Nd isotope systematics of mare basalt 10017

ABSTRACTThe genesis of subduction-related magmas in the Andean region of South America and the Antarctic Peninsula is considered in relation to the Palaeozoic to Cenozoic granitoids belts which are thought to parallel palaeo-coastlines. Their Sr-Nd isotope systematics show a wide range of initial compositions (87Sr/86Sr0 0·7038 to >0·710; εNd, +4 to –10) requiring material input from both depleted mantle and continental crust. In local transects there are consistent trends with time of emplacement, from enriched (crustal) to depleted (mantle) sources, regardless of the sense of migration of magmatism (towards or away from the continent). These trends represent mixing between mantle-derived material and anatectic melts of the lower crust: in each case the crustal end-member reflects the age and isotopic composition of the local deep crustal basement (Precambrian in the easternmost Andes, Palaeozoic in the W and in the Antarctic Peninsula). The depleted end-member could be derived by melting within the subducted oceanic crust, the overlying mantle or previously crystallised mafic underplating. One of the most important factors controlling the mixing process is the angle of subduction, resulting in magma generation under variable tectonic conditions.

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Depleted mantle sources through time: Evidence from Lu–Hf and Sm–Nd isotope systematics of Archean komatiites

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2010.07.012 ◽

2010 ◽

Vol 297 (3-4) ◽

pp. 598-606 ◽

Cited By ~ 108

Author(s):

Janne Blichert-Toft ◽

Igor S. Puchtel

Keyword(s):

Nd Isotope ◽

Depleted Mantle ◽

Mantle Sources ◽

Isotope Systematics

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Pb, Sr and Nd isotope systematics of metavolcanic rocks of the Hutti greenstone belt, Eastern Dharwar craton: Constraints on age, duration of volcanism and evolution of mantle sources during Late Archean

Journal of Asian Earth Sciences ◽

10.1016/j.jseaes.2010.02.010 ◽

2010 ◽

Vol 39 (1-2) ◽

pp. 1-11 ◽

Cited By ~ 48

Author(s):

R. Anand ◽

S. Balakrishnan

Keyword(s):

Greenstone Belt ◽

Dharwar Craton ◽

Eastern Dharwar Craton ◽

Nd Isotope ◽

Metavolcanic Rocks ◽

Mantle Sources ◽

Isotope Systematics

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Geochemistry and Nd‐isotope systematics of chemical and terrigenous sediments from the Dun Mountain Ophiolite, New Zealand

New Zealand Journal of Geology and Geophysics ◽

10.1080/00288306.2002.9514983 ◽

2002 ◽

Vol 45 (4) ◽

pp. 427-451 ◽

Cited By ~ 10

Author(s):

W. J. Sivell

Keyword(s):

New Zealand ◽

Nd Isotope ◽

Terrigenous Sediments ◽

Isotope Systematics

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Ore and Geochemical Specialization and Substance Sources of the Ural and Timan Carbonatite Complexes (Russia): Insights from Trace Element, Rb–Sr, and Sm–Nd Isotope Data

Minerals ◽

10.3390/min11070711 ◽

2021 ◽

Vol 11 (7) ◽

pp. 711

Author(s):

Irina Nedosekova ◽

Nikolay Vladykin ◽

Oksana Udoratina ◽

Boris Belyatsky

Keyword(s):

Trace Element ◽

Mantle Source ◽

Crustal Evolution ◽

Trace Element Data ◽

The Urals ◽

Nd Isotope ◽

Enriched Mantle ◽

Depleted Mantle ◽

Mantle Sources ◽

Geochemical Specialization

The Ilmeno–Vishnevogorsk (IVC), Buldym, and Chetlassky carbonatite complexes are localized in the folded regions of the Urals and Timan. These complexes differ in geochemical signatures and ore specialization: Nb-deposits of pyrochlore carbonatites are associated with the IVC, while Nb–REE-deposits with the Buldym complex and REE-deposits of bastnäsite carbonatites with the Chetlassky complex. A comparative study of these carbonatite complexes has been conducted in order to establish the reasons for their ore specialization and their sources. The IVC is characterized by low 87Sr/86Sri (0.70336–0.70399) and εNd (+2 to +6), suggesting a single moderately depleted mantle source for rocks and pyrochlore mineralization. The Buldym complex has a higher 87Sr/86Sri (0.70440–0.70513) with negative εNd (−0.2 to −3), which corresponds to enriched mantle source EMI-type. The REE carbonatites of the Chetlassky сomplex show low 87Sr/86Sri (0.70336–0.70369) and a high εNd (+5–+6), which is close to the DM mantle source with ~5% marine sedimentary component. Based on Sr–Nd isotope signatures, major, and trace element data, we assume that the different ore specialization of Urals and Timan carbonatites may be caused not only by crustal evolution of alkaline-carbonatite magmas, but also by the heterogeneity of their mantle sources associated with different degrees of enrichment in recycled components.

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Non-linear dynamics, chaos, complexity and enclaves in granitoid magmas

Earth and Environmental Science Transactions of the Royal Society of Edinburgh ◽

10.1017/s0263593300006623 ◽

1996 ◽

Vol 87 (1-2) ◽

pp. 217-223 ◽

Cited By ~ 52

Author(s):

James Flinders ◽

John D. Clemens

Keyword(s):

Deterministic Chaos ◽

Interfacial Area ◽

Two Dimensions ◽

Mixing Processes ◽

Nd Isotope ◽

Natural Systems ◽

Non Linear ◽

The Difference ◽

Magma System ◽

Isotope Systematics

ABSTRACT:Most natural systems display non-linear dynamic behaviour. This should be true for magma mingling and mixing processes, which may be chaotic. The equations that most nearly represent how a chaotic natural system behaves are insoluble, so modelling involves linearisation. The difference between the solution of the linearised and ‘true’ equation is assumed to be small because the discarded terms are assumed to be unimportant. This may be very misleading because the importance of such terms is both unknown and unknowable. Linearised equations are generally poor descriptors of nature and are incapable of either predicting or retrodicting the evolution of most natural systems. Viewed in two dimensions, the mixing of two or more visually contrasting fluids produces patterns by folding and stretching. This increases the interfacial area and reduces striation thickness. This provides visual analogues of the deterministic chaos within a dynamic magma system, in which an enclave magma is mingling and mixing with a host magma. Here, two initially adjacent enclave blobs may be driven arbitrarily and exponentially far apart, while undergoing independent (and possibly dissimilar) changes in their composition. Examples are given of the wildly different morphologies, chemical characteristics and Nd isotope systematics of microgranitoid enclaves within individual felsic magmas, and it is concluded that these contrasts represent different stages in the temporal evolution of a complex magma system driven by nonlinear dynamics. If this is true, there are major implications for the interpretation of the parts played by enclaves in the genesis and evolution of granitoid magmas.

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