The Cuyano proto-ocean between the Chilenia and Cuyania terranes: rifting and plume interaction during the Neoproterozoic – early Palaeozoic evolution of the SW Gondwana margin

Abstract The Precordillera mafic–ultramafic belt (PMUB), located in central-western Argentina, comprises mafic and ultramafic bodies interlayered and/or in tectonic contact with marine siliciclastic units. Whole-rock, mineral geochemistry and Nd–Sr isotope analyses performed in magmatic rocks suggest a relatively different spatial and temporal evolution along the belt. The southern PMUB (south of 32° S) evolved as an intra-continental rifted margin with an enriched mid-ocean-ridge basalt (E-MORB) tholeiitic to alkaline magmatism, to a proto-ocean basin (the Cuyano proto-ocean) with tholeiitic normal-MORB geochemical signature. Based on neodymium model ages (TDM), the magmatic activity started during the late Neoproterozoic Era and continued into the early Palaeozoic Era. Instead, the northern PMUB (28–32° S) evolved as an intra-continental rifted margin with dominant tholeiitic E-MORB to continental flood basalt (CFB) magmatism during the early Palaeozoic Era. ϵNd values (+3.4 to +8.4), rare earth element trends and high-field-strength element systematics, together with an estimated potential mantle temperature of c. 50–100°C above ambient mantle, suggest the PMUB magmatism derived from an enriched mantle source related to the effect of a rising plume linked to the Iapetus Ocean opening. In particular, TDM estimations of 600–550 Ma agree with reported magmatism in central to southern Appalachians. The magmatism in the PMUB, and those registered in the Neoproterozoic Catoctin Formation and in the Southern Oklahoma Aulacogen in the conjugated Laurentian margin, seem to be contemporaneous, sharing a similar plume-enriched mantle source. In this context, the E-MORB signature identified along the PMUB can be described as a plume-distal ridge tectonic setting over an extended margin.

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Geochemical Characteristics and Analysis of Tectonic Setting of Hannuoba Basalts from Chifeng Region, Inner Mongolia

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.734-737.340 ◽

2013 ◽

Vol 734-737 ◽

pp. 340-343

Author(s):

Yan Dong Peng ◽

Zhi Bin Zhang

Keyword(s):

Inner Mongolia ◽

Tectonic Setting ◽

Flood Basalt ◽

Negative Anomaly ◽

Continental Flood Basalt ◽

Continental Plate ◽

Incompatible Elements ◽

Compatible Elements ◽

Low K ◽

Deep Fracture

The Hannuoba basalts from Chifeng region, Inner Mongolia, are continental flood basalt, produced by fissure-t type volcanism in the Miocene. The basalts chemically belong to the tholeiitic series. On the whole, the petrologic compositions are homogeneous. The basalts is characterized by Al2O3 = 11.5%~13.0%, Na2O> K2O and TiO2=1.93~3.29%, chemically belong to the calc-alkaline series with low K2O, which are the agpaitic type; The total amounts of REE of Hannuoba basalts are lower and rich in LREE. There is a weak Eu negative anomaly and weak Ce negative anomaly. The basalts are obviously enriched in incompatible elements (K, Rb, Sr, Zr, Ba, LREE etc.), and depleted in high field-strength element (U,HREE) as well as compatible elements (Co, Ni, Cr etc.).Comprehensive studies have shown that Hannuoba basalts erupted in a stable setting within continental plate and controlled by deep fracture crossed mantle, belonging to continental rift basalt.

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Comparative Geothermometry in High-Mg Magmas from the Etendeka Province and Constraints on their Mantle Source

Journal of Petrology ◽

10.1093/petrology/egaa016 ◽

2019 ◽

Vol 60 (12) ◽

pp. 2509-2528

Author(s):

Zhiguo Cheng ◽

Tong Hou ◽

Jakob K Keiding ◽

Ilya V Veksler ◽

Vadim S Kamenetsky ◽

...

Keyword(s):

Trace Element ◽

Mantle Source ◽

Melt Inclusions ◽

Relative Proportion ◽

Flood Basalt ◽

Reliable Estimate ◽

Thermal Plume ◽

Continental Flood Basalt ◽

Rock Composition ◽

Liquidus Temperatures

Abstract There is still debate whether Large Igneous Provinces (LIPs) are caused by high mantle temperatures induced by thermal plumes or by other factors that enhance melt production from the mantle. A prerequisite for assessing the thermal plume model is a reliable estimate of liquidus temperatures of the magmas produced, preferably based on more than one method of geothermometry. The study reported here compares multiple geothermometers for the Etendeka LIP, which is among the largest Phanerozoic examples and one that shows several features suggestive of a plume origin (continental flood basalt province linked via an age-progressive volcanic ridge to an active hotspot). Magnesium (Mg)-rich magmas emplaced as dikes in NW Namibia are the most primitive rocks known from this province and are thus best suited to determine the composition and melting conditions of their mantle source. Earlier studies of the Etendeka Mg-rich dikes reported high liquidus temperatures based on olivine-melt Mg–Fe equilibria. We extend that work to a larger set of samples and compare the results of olivine-melt Mg–Fe thermometry with other methods based on spinel-melt and spinel–olivine equilibria (Al-in-olivine thermometry), as well as olivine-melt trace-element exchange (Sc/Y thermometry and V oxybarometry). All methods used the same starting assumptions of nominally anhydrous melts and a crystallization pressure of 0·5 GPa. Only mineral-melt or mineral-mineral pairs consistent with compositional equilibrium were used for calculating temperatures. The trace-element compositions of olivine are also used to discuss the relative proportion of peridotite and pyroxenite in the mantle source for these magmas. Twelve dike samples were studied, with whole-rock MgO concentrations ranging from 8·4 to 19·4 wt %. Diagnostic element ratios of transition metals in olivine (e.g., Mn/Fe, Mn/Zn, Zn/Fe) indicate a peridotite-dominated mantle source for the magmas, which is consistent with the other indicators based on whole-rock data e.g., 10 000×Zn/Fe, CaO–MgO trend, FeO/MnO and FC3MS (FeO/CaO–3×MgO/SiO2). The temperature variations show a positive correlation with the Fo-content of host olivines, and values from high-Fo olivine agree well with olivine and spinel liquidus temperatures calculated from thermodynamic models of bulk-rock composition. All methods and most samples yielded a temperature range between 1300 °C and 1400 °C. An exceptional few samples returned temperatures below 1300 °C, the minimum being 1193 °C, whereas several samples yielded temperatures above 1400 °C, the upper range being 1420–1440°C, which we consider to be a robust estimate of the maximum liquidus temperatures for the high-Mg magmas studied. The conversion to mantle potential temperatures is complicated by uncertain depth and degree of melting, but the functional relationship between Tp and primary melt MgO contents, using melt inclusions from olivine phenocrysts with of Fo > 90, indicate a Tp range from 1414 to 1525 °C ( 42 °C), which is 100–150°C higher than estimates of ambient upper mantle Tp in the South Atlantic today.

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A historical approach to continental flood basalt volcanism: insights into pre-volcanic rifting, sedimentation, and early alkaline magmatism

Earth and Planetary Science Letters ◽

10.1016/s0012-821x(99)00045-x ◽

1999 ◽

Vol 168 (1-2) ◽

pp. 19-26 ◽

Cited By ~ 40

Author(s):

H.C. Sheth

Keyword(s):

Flood Basalt ◽

Alkaline Magmatism ◽

Continental Flood Basalt ◽

Historical Approach

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Petrochemistry and tectonic setting of Lower Cretaceous tholeiites from Franz Josef Land, U.S.S.R.

Bulletin of the Geological Society of Denmark ◽

10.37570/bgsd-1988-37-04 ◽

1988 ◽

Vol 37 ◽

pp. 31-49

Author(s):

J. C. Bailey ◽

C. K. Brooks

Keyword(s):

Mantle Source ◽

Lower Cretaceous ◽

Tectonic Setting ◽

Mineral Chemistry ◽

Tholeiitic Basalt ◽

Ocean Basin ◽

The Arctic ◽

Franz Josef Land ◽

Depleted Mantle ◽

The Arctic Ocean

The whole-rock geochemistry and mineral chemistry of six samples of Lower Cretaceous tholeiitic basalt from Franz Josef Land, U.S.S.R., have been studied. Geochemical criteria indicate that the basalts are initial rifting tholeiites characterised by low contents of Ti and other H-elements, suggesting derivation from a depleted mantle source. These tholeiites formed during a Lower Cretaceous rifting stage in the formation of the Arctic Ocean basin, most likely the opening of the Canada Basin.

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Geochemistry of basic magmatism of Western Antarctic Rift: implications for volatiles storage and recycling in the mantle

10.5194/egusphere-egu2020-16794 ◽

2020 ◽

Author(s):

Pier Paolo Giacomoni ◽

Carmelo Ferlito ◽

Costanza Bonadiman ◽

Federico Casetta ◽

Luisa Ottolini ◽

...

Keyword(s):

Mantle Source ◽

Melt Inclusions ◽

Secondary Ion Mass Spectrometry ◽

Alkaline Magmatism ◽

Spinel Lherzolite ◽

Enriched Mantle ◽

Global Comparison ◽

Victoria Land ◽

Basic Magmatism ◽

Petrologic Study

The petrologic study of olivine-hosted melt inclusions (MIs) from alkaline primary Cenozoic basalts of Northern Victoria Land (Antarctica) provide new insights on the role of volatiles in the onset of rift-related magmatism. The concentration of volatile species (H2O, CO2, F, Cl) have been determined by Secondary Ion Mass Spectrometry (SIMS) on a selection of MIs which have been previously re-homogenized at high pressure and temperature conditions in order to avoid any heterogeneity and reducing the H diffusion. The least differentiated MIs vary in composition from basanitic to alkaline basalts, analogously to what is found in McMurdo volcanics, while their volatile concentrations reach up to 2.64 wt% H2O, 3900 ppm CO2, 1377 ppm F and 1336 Cl. Taking into account the most undegassed MIs a H2O/(H2O+CO2) ratio equal to 0.88 was determined, which in turn brings the CO2 content in the basanitic melt with the highest water content up to 8800 ppm.Major and trace element melting modelling indicate that basanite and alkali basalt composition can be reproduced by 3 and 7% of partial melting of an amphibole-bearing spinel lherzolite respectively. Assuming a perfect incompatible behavior for H2O and CO2 these melting proportions allow to constrain the water and CO2 contents in the mantle source in the range 780-840 and 264-273 ppm respectively. The resulting CO2/Nb, CO2/Ba and H2O/Ce ratio are lower than those estimated for Depleted MORB Mantle (DMM), suggesting that the NVL Cenozoic alkaline magmatism could be originated by an enriched mantle source composed by a range from 70% to 60% of Enriched Mantle (EM) and from 30% to 40% of Depleted Morb Mantle (DMM).A global comparison of fluid-related, highly incompatible and immobile/low incompatible elements such as Li, K, Cl, Ba, Nb, Dy and Yb allow to put forward that the prolonged (~500 to 100 Ma) Ross subduction event played a fundamental role in &#160;providing the volatile budget into the lithospheric mantle before the onset of the Cenozoic continental rifting.

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Geochemical and Sr–Nd isotopic constraints on the mantle source of Neoproterozoic mafic dikes of the rifted eastern Laurentian margin, north-central Appalachians, USA

Lithos ◽

10.1016/j.lithos.2014.11.011 ◽

2015 ◽

Vol 212-215 ◽

pp. 202-213 ◽

Cited By ~ 15

Author(s):

Richard A. Volkert ◽

Mark D. Feigenson ◽

Sara Mana ◽

Louise Bolge

Keyword(s):

Mantle Source ◽

North Central ◽

Central Appalachians ◽

Laurentian Margin ◽

Isotopic Constraints

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Geochemistry of Ferrar Dolerite sills and dykes at Terra Cotta Mountain, south Victoria Land, Antarctica

Antarctic Science ◽

10.1017/s0954102095000113 ◽

1995 ◽

Vol 7 (1) ◽

pp. 73-85 ◽

Cited By ~ 11

Author(s):

A.D. Morrison ◽

A. Reay

Keyword(s):

Trace Element ◽

Mantle Source ◽

Source Region ◽

Crustal Component ◽

Enriched Mantle ◽

Victoria Land ◽

Trace Element Signature ◽

Geochemical Variation ◽

Element Enrichment ◽

Taylor Glacier

At Terra Cotta Mountain, in the Taylor Glacier region of south Victoria Land, a 237 m thick Ferrar Dolerite sill is intruded along the unconformity between basement granitoids and overlying Beacon Supergroup sedimentary rocks. Numerous Ferrar Dolerite dykes intrude the Beacon Supergroup and represent later phases of intrusion. Major and trace element data indicate variation both within and between the separate intrusions. Crystal fractionation accounts for much of the geochemical variation between the intrusive events. However, poor correlations between many trace elements require the additional involvement of open system processes. Chromium is decoupled from highly incompatible elements consistent with behaviour predicted for a periodically replenished, tapped and fractionating magma chamber. Large ion lithophile element-enrichment and depletion in Nb, Sr, P and Ti suggests the addition of a crustal component or an enriched mantle source. The trace element characteristics of the Dolerites from Terra Cotta Mountain are similar to those of other Ferrar Group rocks from the central Transantarctic Mountains and north Victoria Land, as well as with the Tasmanian Dolerites. This supports current ideas that the trace element signature of the Ferrar Group is inherited from a uniformly enriched mantle source region.

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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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