Geochemical constraints on Eocene–Miocene geodynamic and magmatic evolution of the Varan-Naragh area, Urumieh-Dokhtar Magmatic Arc, Iran

Two different types of igneous rock formed during separate Cenozoic magmatic phases in the Varan-Naragh area in the central part of the Urumieh-Dokhtar Magmatic Arc (UDMA) of Iran as a part of the Alpine-Himalayan system. The first phase comprises late Eocene – early Oligocene Naragh gabbroic rocks (Ns), and the second phase is characterized by the emplacement of both volcanic and plutonic rocks of the early Miocene. Both phases display moderate enrichment of large rare earth elements and depletion of high field strength elements coupled with negative Nb, Ti, and P anomalies, indicative of subduction-related magmatic events within an active continental margin. Initial values of 87Sr/86Sr and εNdT are 0.70684 and +0.15 and 0.70560–0.70654 and +2.55 to +3.49 for Ns and early Miocene intrusive and volcanic rocks, respectively. Comparisons of rare earth element patterns and mantle-like isotopic ratios suggest that Ns mafic and early Miocene magmatic rocks were derived from partial melting of a common subcontinental lithospheric mantle. Geochemical and isotopic ratios of Ns gabbroic rocks, in combination with the data related to other coeval and proximal mafic-intermediate intrusions (such as Nashalj), suggest enrichment of the lithospheric mantle by slab-derived fluids with a minor subducted sediment melt. The low εNdT of Ns gabbroic rocks can reflect involvement of slab-derived components. The geochemical similarity and the close spatial and temporal association of Varan intrusive and volcanic rocks suggest a common petrogenetic relationship. Geochemical, isotopic, and geochronological evidence from the region indicate three major phases of igneous activity in the Kashan magmatic segment of the central UDMA during late Eocene to Miocene, resulting in complex tectonic regime transition from compressional subduction to extensional post-collisional settings. Integrated with published studies, the new results support a model suggesting that subduction-related magmatic activity was still influencing the central UDMA in the early Miocene time and are also consistent with the notion of oblique and diachronous collision along the northeast margin of the Arabia plate.

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Geochemistry and tectonic environment of the Şarkışla area volcanic rocks in central Anatolia, Turkey

Mineralogical Magazine ◽

10.1180/minmag.1987.051.362.09 ◽

1987 ◽

Vol 51 (362) ◽

pp. 553-559 ◽

Cited By ~ 21

Author(s):

E. Gökten ◽

P. A. Floyd

Keyword(s):

Upper Cretaceous ◽

Active Continental Margin ◽

Volcanic Rocks ◽

Central Anatolia ◽

Magmatic Arc ◽

Early Tertiary ◽

Tectonic Environment ◽

Geochemical Study ◽

Lithological Composition ◽

Back Arc

AbstractThe volcanic rocks of the Şarkışla area in northeastern central Anatolia are associated with volcaniclastics, turbiditic limestones and pelagic-hemipelagic shales of Upper Cretaceous-Palaeocene age. A preliminary geochemical study was undertaken to constrain local tectonic models, and due to the variable altered nature of the volcanics, determine the lithological composition and magma type. Chemically the volcanics are an andesite-dominated suite of calc-alkali lavas, probably developed adjacent to an active continental margin in a local (ensialic back-arc?) basinal area. The volcanic activity was probably related to a postulated magmatic arc just south of the area during the early Tertiary.

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Evolution of deep mantle sourced carbonated melt in the mantle lithosphere

10.5194/egusphere-egu2020-13055 ◽

2020 ◽

Author(s):

Guoliang Zhang

Keyword(s):

Rare Earth ◽

Field Strength ◽

Rare Earth Elements ◽

Lithospheric Mantle ◽

High Field ◽

Volcanic Rocks ◽

Mantle Lithosphere ◽

High Field Strength ◽

Alkali Basalts ◽

Deep Mantle

Deep sourced magmas play a key role in distribution of carbon in the Earth&#8217;s system. Oceanic hotspots rooted in deep mantle usually produce CO2-rich magmas. However, the association of CO2 with the origin of these magmas remains unclear. Here we report geochemical analyses of a suite of volcanic rocks from the Caroline Seamount Chain formed by the deep-rooted Caroline hotspot in the western Pacific. The most primitive magmas have depletion of SiO2 and high field strength elements and enrichment of rare earth elements that are in concert with mantle-derived primary carbonated melts. The carbonated melts show compositional variations that indicate reactive evolution within the overlying mantle lithosphere and obtained depleted components from the lithospheric mantle. The carbonated melts were de-carbonated and modified to oceanic alkali basalts by precipitation of perovskite, apatite and ilmenite that significantly decreased the concentrations of rare earth elements and high field strength elements. These magmas experienced a stage of non-reactive fractional crystallization after the reactive evolution was completed. Thus, the carbonated melts would experience two stages, reactive and un-reactive, of evolution during their transport through in thick oceanic lithospheric mantle. We suggest that the mantle lithosphere plays a key role in de-carbonation and conversion of deep-sourced carbonated melts to alkali basalts. This work was financially supported by the National Natural Science Foundation of China (91858206, 41876040).

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DEVELOPMENT OF THE TERTIARY OFFSHORE PAPUAN BASIN

The APPEA Journal ◽

10.1071/aj74006 ◽

1975 ◽

Vol 15 (1) ◽

pp. 55 ◽

Cited By ~ 2

Author(s):

N. C. Tallis

Keyword(s):

Late Eocene ◽

Early Miocene ◽

Second Phase ◽

The West ◽

Fine Grained ◽

Early Oligocene ◽

Coral Sea ◽

Clastic Sediments ◽

Marine Seismic ◽

Rigid Segment

Marine seismic studies combined with wildcat drilling in the Gulf of Papua have provided a comprehensive insight into the geology of the offshore Papuan Basin. The Basin adjoins a downwarped but structurally rigid segment of the Australian continental shield in the west, and the Coral Sea Basin in the southeast. It incorporates arcuate geosynclinal development eastward and northward beyond the continental margin. The pre-Tertiary history is relatively obscure. Jurassic-Lower Cretaceous clastic sediments overlie granites and volcanics of the continental shield in the west. Eastward, the record is masked by great thicknesses of Tertiary strata, and the pre-Tertiary may be represented in outcrop by a metamorphic series of indeterminate age.The Tertiary offshore basin developed in three distinct phases, commencing in Late Cretaceous/Early Eocene time, when seas transgressed from east to west across a peneplaned surface. An eastward-thickening wedge of argillaceous limestones and cherts was deposited. Regression and erosion occurred in Late Eocene/Early Oligocene time, possibly in association with upwarp of the oceanic crust, which created an eastern volcanic borderland. Typical orthogeosynclinal sedimentation followed in Early Miocene time, with reef, shoal and pelagic limestones deposited marginal to the stable western (continental) shelf, and with prolific volcanism associated with the eastern (oceanic) flank. This volcanism was the source for a thick pile of mudstone-greywacke sediments which was deposited in an intermediate eugeosyncline.This second phase was modified in Late Miocene time by regional uplift, and by development of the Central Mountain geanticlinal belt. This created an immense southeasterly pro-grading system which rapidly buried the Early Miocene profile. These fine grained clastic Plio-Pleistocene sediments have been highly deformed by gravitational and diapiric influences in the east-central portion of the basin. Huge volumes of sediment are still being transported southeastward into the Coral Sea Basin.

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Time-evolution of magma sources in a continental back-arc setting: the Cenozoic basalts from Sierra de San Bernardo (Patagonia, Chubut, Argentina)

Geological Magazine ◽

10.1017/s0016756808004949 ◽

2008 ◽

Vol 145 (5) ◽

pp. 714-732 ◽

Cited By ~ 27

Author(s):

SANDRO BRUNI ◽

MASSIMO D'ORAZIO ◽

MIGUEL J. HALLER ◽

FABRIZIO INNOCENTI ◽

PIERO MANETTI ◽

...

Keyword(s):

Current Knowledge ◽

Volcanic Rocks ◽

Late Eocene ◽

Early Miocene ◽

Alkaline Magmatism ◽

Pb Isotope ◽

Asthenospheric Mantle ◽

Magma Sources ◽

Oceanic Plates ◽

Patagonian Andes

AbstractEast of the Patagonian Andes, mafic volcanic rocks (mainly lava flows and scoriae) are exposed in the Sierra de San Bernardo fold belt and neighbouring areas (central Patagonia; 44.5–46° S, 69–71° W). They were erupted over a wide interval of time (late Eocene–Pleistocene; 14 new K–Ar ages), and show systematic chemical and Sr–Nd–Pb isotopic variations in time. The alkaline lavas (Mg number 57–66) erupted during the late Eocene and early Miocene, have an intraplate geochemical affinity, and have the highest 143Nd/144Nd and 206Pb/204Pb and the lowest 87Sr/86Sr ratios of the dataset. Their compositions indicate that their depth of equilibration in the mantle was greater than that of subsequent lavas. In contrast, the Plio-Pleistocene alkaline lavas (Mg number 58–71) are the most enriched in incompatible elements, still showing an intra-plate signature, and have the lowest 143Nd/144Nd and 206Pb/204Pb and the highest 87Sr/86Sr ratios. A distinctive group of early Miocene subalkaline lavas is characterized by slightly more evolved compositions (Mg number 56–59), coupled with very low incompatible element contents, flat LREE and fractionated HREE patterns (‘kinked’ pattern), and intermediate Sr–Nd–Pb isotope compositions. The Pleistocene basanites (Mg number 71–72) from the Cerro Ante monogenetic cone, on the easternmost slopes of the Patagonian Andes, have a marked orogenic geochemical signature and Sr–Nd–Pb isotope ratios that overlap with those of volcanic rocks from the adjacent active Andean arc. They originated in a mantle source extensively modified by the addition of materials from the subducting Pacific oceanic plates. We suggest that the wide chemical and isotopic variability of the Sierra de San Bernardo lavas reflects the upwelling of asthenospheric mantle beneath the study area, which induced lithospheric erosion and progressive involvement of enriched mantle domains in the genesis of magmas. In this context, late Eocene and early Miocene alkaline magmatism was dominantly sourced from the asthenospheric mantle, whereas Plio-Pleistocene alkaline magmas contain the largest proportion of an enriched lithospheric component. The peculiar compositional features of the early Miocene subalkaline lavas are interpreted in terms of high-degree mantle melting followed by melt–lithospheric mantle reaction processes. Based on current knowledge about the relative movement and decoupling between lithosphere and asthenosphere, we propose that the asthenosphere below the study area rose up to compensate for the westward drift of the mantle wedge coupled with the South American lithosphere.

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

Journal of Geological Research ◽

10.1155/2013/735498 ◽

2013 ◽

Vol 2013 ◽

pp. 1-11 ◽

Cited By ~ 1

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.

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Zircon U–Pb ages, geochemistry and Sr–Nd isotopes of the Golshekanan granitoid, Urumieh–Dokhtar magmatic arc, Iran: evidence for partial melting of juvenile crust

Geological Magazine ◽

10.1017/s0016756820001338 ◽

2020 ◽

pp. 1-16

Author(s):

Fatemeh Sarjoughian ◽

Bahareh Zahedi ◽

Hossein Azizi ◽

Wenli Ling ◽

David R. Lentz ◽

...

Keyword(s):

Partial Melting ◽

Active Continental Margin ◽

Late Eocene ◽

The Body ◽

Central Iran ◽

Primitive Mantle ◽

Magmatic Arc ◽

Juvenile Crust ◽

Continental Lithospheric Mantle ◽

T Values

Abstract The Golshekanan granitoid body is situated in the central part of the Urumieh–Dokhtar magmatic arc (UDMA) in central Iran, and includes granite and granodiorite with minor monzonite and diorite. Zircon U–Pb dating yields a late Eocene (Priabonian) crystallization age of 37.6 ± 0.2 Ma. The body is calc-alkaline and metaluminous to weakly peraluminous (A/CNK ≤ 1.10) with SiO2 ranging from 61.1 to 71.5 wt% and MgO from 0.8 to 3.3 wt%, with Na2O + K2O of 4.0–8.5 wt%. Primitive mantle-normalized trace-element patterns display enrichments in the large-ion lithophile elements (LILE), such as Rb, Cs, Ba and K, and depletion from the high-field-strength elements (HFSEs), such as Nb, Ti, Ta and P. The rocks are enriched in LREEs relative to HREEs (average (La/Yb)CN = 4.3) and exhibit weak negative Eu anomalies (average Eu/Eu* = 0.75), revealing typical active continental margin arc affinity. The low initial 87Sr/86Sr ratios (0.70440–0.70504) and notable positive ϵNd(t) values (+4.0 to +5.2) indicate an origin by partial melting of juvenile rocks in the lower crust, possibly with some involvement of sub-continental lithospheric mantle beneath Central Iran. These processes probably occurred due to the Neo-Tethys oceanic slab retreat and (or) rollback during late Eocene time.

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Eocene development of the northerly active continental margin of the Southern Neotethys in the Kyrenia Range, north Cyprus

Geological Magazine ◽

10.1017/s0016756813000563 ◽

2013 ◽

Vol 151 (4) ◽

pp. 692-731 ◽

Cited By ~ 18

Author(s):

ALASTAIR H.F. ROBERTSON ◽

GILLIAN A. McCAY ◽

KEMAL TASLI ◽

AŞEGÜL YILDIZ

Keyword(s):

Debris Flow ◽

Subduction Zone ◽

Continental Margin ◽

Middle Eocene ◽

Active Continental Margin ◽

Volcanic Rocks ◽

Late Eocene ◽

Calcareous Nannofossils ◽

The North ◽

Thrust Sheets

AbstractWe focus on an active continental margin related to northwards subduction during the Eocene in which sedimentary melange (‘olistostromes’) forms a key component. Maastrichtian – Early Eocene deep-marine carbonates and volcanic rocks pass gradationally upwards into a thick succession (<800 m) of gravity deposits, exposed in several thrust sheets. The lowest levels are mainly siliciclastic turbidites and debris-flow deposits. Interbedded marls contain Middle Eocene planktonic/benthic foraminifera and calcareous nannofossils. Sandstones include abundant ophiolite-derived grains. The higher levels are chaotic debris-flow deposits that include exotic blocks of Late Palaeozoic – Mesozoic neritic limestone and dismembered ophiolite-related rocks. A thinner sequence (<200 m) in one area contains abundant redeposited Paleogene pelagic limestone and basalt. Chemical analysis of basaltic clasts shows that some are subduction influenced. Basaltic clasts from unconformably overlying alluvial conglomerates (Late Eocene – Oligocene) indicate derivation from a supra-subduction zone ophiolite, including boninites. Taking account of regional comparisons, the sedimentary melange is interpreted to have formed within a flexurally controlled foredeep, floored by continental crust. Gravity flows including large limestone blocks, multiple debris flows and turbidites were emplaced, followed by southwards thrust imbrication. The emplacement was possibly triggered by the final closure of an oceanic basin to the north (Alanya Ocean). Further convergence between the African and Eurasian plates was accommodated by northwards subduction beneath the Kyrenia active continental margin. Subduction zone rollback may have triggered collapse of the active continental margin. Non-marine to shallow-marine alluvial fans prograded southwards during Late Eocene – Oligocene time, marking the base of a renewed depositional cycle that lasted until latest Miocene time.

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U-Pb geochronology, Sr-Nd geochemistry, petrogenesis and tectonic setting of Gandab volcanic rocks, northeastern Iran

Geochronometria ◽

10.1515/geochr-2015-0061 ◽

2017 ◽

Vol 44 (1) ◽

pp. 269-286 ◽

Cited By ~ 1

Author(s):

Azam Entezari Harsini ◽

Seyed A Mazaheri ◽

Saeed Saadat ◽

José F Santos

Keyword(s):

Rare Earth ◽

Rare Earth Elements ◽

Rare Earth Element ◽

Earth Element ◽

Saturation Index ◽

Tectonic Setting ◽

Volcanic Rocks ◽

Major Elements ◽

Magmatic Arc ◽

Heavy Rare Earth Elements

Abstract This paper addresses U-Pb geochronology, Sr-Nd geochemistry, petrogenesis and tectonic setting in the Gandab volcanic rocks. The Gandab volcanic rocks belong to the Sabzevar zone magmatic arc (northeastern Iran). Petrographically, all the studied volcanic rocks indicate porphyritic textures with phenocrysts of plagioclase, K-feldespar, hornblende, pyroxene, and magnetite which are embedded in a fine to medium grained groundmass. As well, amygdaloidal, and poikilitic textures are seen in some rocks. The standard chemical classifications show that the studied rocks are basaltic trachy andesite, trachy andesite, trachyte, and trachy dacite. Major elements reveal that the studied samples are metaluminous and their alumina saturation index varies from 0.71 to 1.02. The chondrite-normalized rare earth element and mantle-normalized trace element patterns show enrichment in light rare earth elements (LREE) relative to heavy rare earth elements (HREE) and in large ion lithophile elements (LILE) relative to high field strength elements (HFSE). As well they show a slightly negative Eu anomaly (Eu/Eu* = 0.72 – 0.97). The whole-rock geochemistry of the studied rocks suggests that they are related to each other by fractional crystallization. LA-MC-ICP-MS U-Pb analyses in zircon grains from two volcanic rock samples (GCH-119 and GCH-171) gave ages ranging of 5.47 ± 0.22 Ma to 2.44 ± 0.79 Ma, which corresponds to the Pliocene period. In four samples analysed for Sr and Nd isotopes 87Sr/86Sr ratios range from 0.704082 to 0.705931 and εNd values vary between +3.34 and +5. These values could be regarded to as representing mantle derived magmas. Taking into account the comparing rare earth element (REE) patterns, an origin of the parental magmas in enriched lithospheric mantle is suggested. Finally, it is concluded that Pliocene Gandab volcanic rocks are related to the post-collision environment that followed the Neo-Tethys subduction.

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Studi Awal Geologi di Daerah Beruang Kanan Kabupaten Gunung Mas Propinsi Kalimantan Tengah

PROMINE ◽

10.33019/promine.v6i1.710 ◽

2018 ◽

Vol 6 (1) ◽

pp. 1-11

Author(s):

Retno Anjarwati ◽

Arifudin Idrus ◽

Lucas Donny Setijadji

Keyword(s):

Gold Mineralization ◽

Volcanic Rocks ◽

Gold Deposits ◽

Central Kalimantan ◽

Magmatic Arc ◽

Tertiary Sediment ◽

Copper Gold ◽

Regional Tectonic ◽

Mineralization Processes ◽

High Yields

The regional tectonic conditions of the KSK Contract of Work are located in the mid-Tertiary magmatic arc (Carlile and Mitchell, 1994) which host a number of epithermal gold deposits (eg, Kelian, Indon, Muro) and significant prospects such as Muyup, Masupa Ria, Gunung Mas and Mirah. Copper-gold mineralization in the KSK Contract of Work is associated with a number of intrusions that have occupied the shallow-scale crust at the Mesozoic metamorphic intercellular junction to the south and continuously into the Lower Tertiary sediment toward the water. This intrusion is interpreted to be part of the Oligocene arc of Central Kalimantan (in Carlile and Mitchell 1994) Volcanic rocks and associated volcanoes are older than intrusions, possibly aged Cretaceous and exposed together with all three contacts (Carlile and Mitchell, 1994) some researchers contribute details about the geological and mineralogical background, and some papers for that are published for the Beruang Kanan region and beyond but no one can confirm the genesis type of the Beruang Kanan region The mineralization of the Beruang Kanan area is generally composed by high yields of epithermal sulphide mineralization. with Cu-Au mineralization This high epithermal sulphide deposition coats the upper part of the Cu-Au porphyry precipitate associated with mineralization processes that are generally controlled by the structure

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Petrogenesis of the peralkaline Flowers River Igneous Suite and its significance to the development of the southern Nain Batholith

Geological Magazine ◽

10.1017/s0016756821000388 ◽

2021 ◽

pp. 1-26

Author(s):

Taylor A. Ducharme ◽

Christopher R.M. McFarlane ◽

Deanne van Rooyen ◽

David Corrigan

Keyword(s):

Trace Element ◽

Volcanic Rocks ◽

Second Phase ◽

Discrete Events ◽

Volcanic Event ◽

Volcanic Succession ◽

Intrusive Suite ◽

Tectonic Boundaries ◽

Host Rocks ◽

Nain Plutonic Suite

Abstract The Flowers River Igneous Suite of north-central Labrador comprises several discrete peralkaline granite ring intrusions and their coeval volcanic succession. The Flowers River Granite was emplaced into Mesoproterozoic-age anorthosite–mangerite–charnockite–granite (AMCG) -affinity rocks at the southernmost extent of the Nain Plutonic Suite coastal lineament batholith. New U–Pb zircon geochronology is presented to clarify the timing and relationships among the igneous associations exposed in the region. Fayalite-bearing AMCG granitoids in the region record ages of 1290 ± 3 Ma, whereas the Flowers River Granite yields an age of 1281 ± 3 Ma. Volcanism occurred in three discrete events, two of which coincided with emplacement of the AMCG and Flowers River suites, respectively. Shared geochemical affinities suggest that each generation of volcanic rocks was derived from its coeval intrusive suite. The third volcanic event occurred at 1271 ± 3 Ma, and its products bear a broad geochemical resemblance to the second phase of volcanism. The surrounding AMCG-affinity ferrodiorites and fayalite-bearing granitoids display moderately enriched major- and trace-element signatures relative to equivalent lithologies found elsewhere in the Nain Plutonic Suite. Trace-element compositions also support a relationship between the Flowers River Granite and its AMCG-affinity host rocks, most likely via delayed partial melting of residual parental material in the lower crust. Enrichment manifested only in the southernmost part of the Nain Plutonic Suite as a result of its relative proximity to multiple Palaeoproterozoic tectonic boundaries. Repeated exposure to subduction-derived metasomatic fluids created a persistent region of enrichment in the underlying lithospheric mantle that was tapped during later melt generation, producing multiple successive moderately to strongly enriched magmatic episodes.

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