scholarly journals Iron-Copper-Zinc Isotopic Compositions of Andesites from the Kueishantao Hydrothermal Field off Northeastern Taiwan

2021 ◽  
Vol 14 (1) ◽  
pp. 359
Author(s):  
Zhigang Zeng ◽  
Xiaohui Li ◽  
Shuai Chen ◽  
Yuxiang Zhang ◽  
Zuxing Chen ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Hydrothermal Field ◽  
Andesitic Magma ◽  
Isotopic Compositions ◽  
Stable Isotope Fractionation ◽  
Relative Enrichment ◽  
Wide Range ◽  
Sedimentary Carbonate ◽  
Cu And Zn ◽  
Zn Isotopes

The studies of iron (Fe), copper (Cu), and zinc (Zn) isotopic compositions in seafloor andesites are helpful in understanding the metal stable isotope fractionation during magma evolution. Here, the Fe, Cu, and Zn isotopic compositions of andesites from the Kueishantao hydrothermal field (KHF) off northeastern Taiwan, west Pacific, have been studied. The majority of δ56Fe values (+0.02‰ to +0.11‰) in the KHF andesites are consistent with those of MORBs (mid-ocean ridge basalts). This suggests that the Fe in the KHF andesites is mainly from a MORB-type mantle. The Fe-Cu-Zn isotopic compositions (δ56Fe +0.22‰, δ65Cu +0.16‰ to +0.64‰, and δ66Zn +0.29‰ to +0.71‰) of the KHF andesites, which are significantly different from those of the MORBs and the continental crust (CC), have a relatively wide range of Cu and Zn isotopic compositions. This is most likely to be a result of the entrainment of the sedimentary carbonate-derived components into an andesitic magma. The recycled altered rocks (higher δ56Fe, lower δ66Zn) could preferentially incorporate isotopically light Fe and heavy Zn into the magma, resulting in relative enrichment of the lighter Fe and heavier Zn isotopes in the andesites. The majority of the δ56Fe values in the KHF andesites are higher than those of the sediments and the local CC and lower than those of the subducted altered rocks, while the reverse is true for δ66Zn, suggesting that the subseafloor sediments and CC materials (lower δ56Fe, higher δ66Zn) contaminating the rising andesitic magma could preferentially incorporate isotopically heavy Fe and light Zn into the magma, resulting in relative enrichment of the heavier Fe and lighter Zn isotopes in the andesites. Thus, the characteristics of the Fe and Zn isotopes in back-arc and island-arc volcanic rocks may also be influenced by the CC and plate subduction components.

Age, geochemistry and Sr-Nd-Pb isotopic compositions of alkali volcanic rocks from Mt. Melbourne and the western Ross Sea, Antarctica

2015 ◽  
Vol 19 (4) ◽  
pp. 681-695 ◽  
Author(s):  
Mi Jung Lee ◽  
Jong Ik Lee ◽  
Tae Hoon Kim ◽  
Joohan Lee ◽  
Keisuke Nagao
Keyword(s):  
Ross Sea ◽  
Volcanic Rocks ◽  
Isotopic Compositions ◽  
Western Ross Sea

Early Cretaceous crust–mantle interaction linked to rollback of the Palaeo-Pacific flat-subducting slab: constraints from the intermediate–felsic volcanic rocks of the northern Great Xing’an Range, NE China

2021 ◽  
pp. 1-22
Author(s):  
Jia-Hao Jing ◽  
Hao Yang ◽  
Wen-Chun Ge ◽  
Yu Dong ◽  
Zheng Ji ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
Ne China ◽  
Asthenospheric Mantle ◽  
High K ◽  
Wide Range ◽  
Great Xing’An Range ◽  
Subducting Slab

Abstract Late Mesozoic igneous rocks are important for deciphering the Mesozoic tectonic setting of NE China. In this paper, we present whole-rock geochemical data, zircon U–Pb ages and Lu–Hf isotope data for Early Cretaceous volcanic rocks from the Tulihe area of the northern Great Xing’an Range (GXR), with the aim of evaluating the petrogenesis and genetic relationships of these rocks, inferring crust–mantle interactions and better constraining extension-related geodynamic processes in the GXR. Zircon U–Pb ages indicate that the rhyolites and trachytic volcanic rocks formed during late Early Cretaceous time (c. 130–126 Ma). Geochemically, the highly fractionated I-type rhyolites exhibit high-K calc-alkaline, metaluminous to weakly peraluminous characteristics. They are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) but depleted in high-field-strength elements (HFSEs), with their magmatic zircons ϵHf(t) values ranging from +4.1 to +9.0. These features suggest that the rhyolites were derived from the partial melting of a dominantly juvenile, K-rich basaltic lower crust. The trachytic volcanic rocks are high-K calc-alkaline series and exhibit metaluminous characteristics. They have a wide range of zircon ϵHf(t) values (−17.8 to +12.9), indicating that these trachytic volcanic rocks originated from a dominantly lithospheric-mantle source with the involvement of asthenospheric mantle materials, and subsequently underwent extensive assimilation and fractional crystallization processes. Combining our results and the spatiotemporal migration of the late Early Cretaceous magmatic events, we propose that intense Early Cretaceous crust–mantle interaction took place within the northern GXR, and possibly the whole of NE China, and that it was related to the upwelling of asthenospheric mantle induced by rollback of the Palaeo-Pacific flat-subducting slab.

Le terrane de Slide Mountain (Cordillères canadiennes) : une lithosphère océanique marquée par des points chauds

2003 ◽  
Vol 40 (6) ◽  
pp. 833-852 ◽  
Author(s):  
M Tardy ◽  
H Lapierre ◽  
D Bosch ◽  
A Cadoux ◽  
A Narros ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Oceanic Island ◽  
Light Rare Earth ◽  
Isotopic Compositions ◽  
Incompatible Elements ◽  
Depleted Mantle ◽  
Mantle Sources ◽  
British Colombia ◽  
Ultramafic Cumulates ◽  
Back Arc

The Slide Mountain Terrane consists of Devonian to Permian siliceous and detrital sediments in which are interbedded basalts and dolerites. Locally, ultramafic cumulates intrude these sediments. The Slide Mountain Terrane is considered to represent a back-arc basin related to the Quesnellia Paleozoic arc-terrane. However, the Slide Mountain mafic volcanic rocks exposed in central British Colombia do not exhibit features of back-arc basin basalts (BABB) but those of mid-oceanic ridge (MORB) and oceanic island (OIB) basalts. The N-MORB-type volcanic rocks are characterized by light rare-earth element (LREE)-depleted patterns, La/Nb ratios ranging between 1 and 2. Moreover, their Nd and Pb isotopic compositions suggest that they derived from a depleted mantle source. The within-plate basalts differ from those of MORB affinity by LREE-enriched patterns; higher TiO2, Nb, Ta, and Th abundances; lower εNd values; and correlatively higher isotopic Pb ratios. The Nd and Pb isotopic compositions of the ultramafic cumulates are similar to those of MORB-type volcanic rocks. The correlations between εNd and incompatible elements suggest that part of the Slide Mountain volcanic rocks derive from the mixing of two mantle sources: a depleted N-MORB type and an enriched OIB type. This indicates that some volcanic rocks of the Slide Mountain basin likely developed from a ridge-centered or near-ridge hotspot. The activity of this hotspot is probably related to the worldwide important mantle plume activity that occurred at the end of Permian times, notably in Siberia.

Geochemistry and Isotope Composition of Paleoproterozoic Granites and Felsic Volcanics of the Elash Graben: Evidence of the Heterogeneity of the Early Precambrian Crust

2021 ◽  
Vol 62 (10) ◽  
pp. 1175-1187
Author(s):  
A.D. Nozhkin ◽  
O.M. Turkina ◽  
K.A. Savko
Keyword(s):  
Isotope Composition ◽  
Volcanic Rocks ◽  
Rare Metal ◽  
Temporal Association ◽  
Metal Deposit ◽  
Wide Range ◽  
Rare Metal Deposit ◽  
Geochronological Study ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

Abstract —The paper presents results of a petrogeochemical and isotope–geochronological study of the granite–leucogranite association of the Pavlov massif and felsic volcanics from the Elash graben (Biryusa block, southwest of the Siberian craton). A characteristic feature of the granite–leucogranites is their spatial and temporal association with vein aplites and pegmatites of the East Sayan rare-metal province. The U–Pb age of zircon from granites of the Pavlov massif (1852 ± 5 Ma) is close to the age of the pegmatites of the Vishnyakovskoe rare-metal deposit (1838 ± 3 Ma). The predominant biotite porphyritic granites and leucogranites of the Pavlov massif show variable alkali ratios (K2O/Na2O = 1.1–2.3) and ferroan (Fe*) index and a peraluminous composition; they are comparable with S-granites. The studied rhyolites of the Tagul River (SiO2 = 71–76%) show a low ferroan index, a high K2O/Na2O ratio (1.6–4.0), low (La/Yb)n values (4.3–10.5), and a clear Eu minimum (Eu/Eu* = 0.3–0.5); they are similar to highly fractionated I-granites. All coeval late Paleoproterozoic (1.88–1.85 Ga) granites and felsic volcanics of the Elash graben have distinct differences in composition, especially in the ferroan index and HREE contents, owing to variations in the source composition and melting conditions during their formation at postcollisions extension. The wide range of the isotope parameters of granites and felsic volcanic rocks (εNd from +2.0 to –3.7) and zircons (εHf from +3.0 to +0.8, granites of the Toporok massif) indicates the heterogeneity of the crustal basement of the Elash graben, which formed both in the Archean and in the Paleoproterozoic.

The (n, d) reaction on Cu and Zn isotopes

1967 ◽  
Vol 93 (1) ◽  
pp. 209-217 ◽  
Author(s):  
G. Chursin ◽  
M. Fazio ◽  
S. Micheletti ◽  
M. Pignanelli ◽  
L. Zetta
Keyword(s):  
Cu And Zn ◽  
Zn Isotopes

scholarly journals The Nordre Strømfjord shear zone and the Arfersiorfik quartz diorite in Arfersiorfik, the Nagssugtoqidian orogen, West Greenland

2006 ◽  
Vol 11 ◽  
pp. 145-162 ◽  
Author(s):  
Kai Sørensen ◽  
John A. Korstgård ◽  
William E. Glassley ◽  
Bo Møller Stensgaard
Keyword(s):  
Shear Zone ◽  
Volcanic Rocks ◽  
Quartz Diorite ◽  
Ductile Deformation ◽  
Chemical Compositions ◽  
West Greenland ◽  
South West ◽  
Wide Range ◽  
Inland Ice ◽  
Zone Deformation

The Nordre Strømfjord shear zone in the fjord Arfersiorfik, central West Greenland, consists of alternating panels of supracrustal rocks and orthogneisses which together form a vertical zone up to 7 km wide with sinistral transcurrent, ductile deformation, which occurred under middle amphibolite facies conditions. The pelitic and metavolcanic schists and paragneisses are all highly deformed, while the orthogneisses appear more variably deformed, with increasing deformation evident towards the supracrustal units. The c. 1.92 Ga Arfersiorfik quartz diorite is traceable for a distance of at least 35 km from the Inland Ice towards the west-south-west. Towards its northern contact with an intensely deformed schist unit it shows a similar pattern of increasing strain, which is accompanied by chemical and mineralogical changes. The metasomatic changes associated with the shear zone deformation are superimposed on a wide range of original chemical compositions, which reflect magmatic olivine and/ or pyroxene as well as hornblende fractionation trends. The chemistry of the Arfersiorfik quartz diorite suite as a whole is comparable to that of Phanerozoic plutonic and volcanic rocks of calc-alkaline affinity.

scholarly journals U–Pb geochronology of epidote by LA–ICP–MS as a tool for dating hydrothermal-vein formation

2020 ◽  
Author(s):  
Veronica Peverelli ◽  
Tanya Ewing ◽  
Daniela Rubatto ◽  
Martin Wille ◽  
Alfons Berger ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
A Priori ◽  
Swiss Alps ◽  
Hydrothermal Vein ◽  
Isotopic Compositions ◽  
Vein Formation ◽  
Icp Ms ◽  
Wide Range ◽  
Primary Reference

Abstract. Monoclinic epidote is a low-µ (µ = 283U / 204Pb) mineral occurring in a variety of geological environments, participating in many metamorphic reactions and stable throughout a wide range of pressure–temperature conditions. Despite containing fair amounts of U, its use as a U–Pb geochronometer has been hindered by the commonly high contents of initial Pb with isotopic compositions that cannot be assumed a priori. We present U–Pb geochronology of hydrothermal-vein epidote spanning a wide range of Pb (3.9–190 µg g−1), Th (0.009–38 µg g−1) and U (2.6–530 µg g−1) contents and with µ values between 7–510 from the Albula area (eastern Swiss Alps), from the Grimsel area (central Swiss Alps) and from the Heyuan fault (Guangdong province, China). The investigated epidote samples show appreciable fractions of initial Pb that vary to different extents. A protocol has been developed for in situ U–Pb dating of epidote by spot-analysis laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) with a magmatic allanite as primary reference material. The suitability of the protocol and the reliability of the measured isotopic ratios have been ascertained by independent measurements of 238U / 206Pb and 207Pb / 206Pb ratios respectively by quadrupole and multicollector ICP–MS applied to epidote micro-separates digested and diluted in acids. For age calculation, we used the Tera–Wasserburg (207Pb / 206Pb–238U / 206Pb) diagram, which does not require corrections for initial Pb and provides the initial 207Pb / 206Pb ratio if all intra-sample analyses are co-genetic. Petrographic and microstructural data indicate that the calculated ages date the crystallization of vein epidote from a hydrothermal fluid and that the U–Pb system was not reset to younger ages by later events. Vein epidote from the Albula area formed in the Paleocene (62.7 ± 3.0 Ma) and is related to Alpine greenschist-facies metamorphism. The Miocene (19.1 ± 4.0 Ma and 16.9 ± 3.7 Ma) epidote veins from the Grimsel area formed during the Handegg phase (22–17 Ma) of the Alpine evolution of the Aar Massif. Identical initial 207Pb / 206Pb ratios reveal homogeneity in Pb isotopic compositions of the fluid across ca. 200 m. Vein epidote from the Heyuan fault is Cretaceous in age (108.1 ± 8.4 Ma) and formed during the early movements of the fault. In situ U–Pb analyses of epidote returned reliable ages of otherwise undatable epidote-quartz veins. The Tera–Wasserburg approach has proven pivotal for in situ U–Pb dating of epidote and the decisive aspect for low age uncertainties is the variability in intra-sample initial Pb fractions.

Subduction-related magmatic imprint of most Philippine ophiolites: implications on the early geodynamic evolution of the Philippine archipelago

2004 ◽  
Vol 175 (5) ◽  
pp. 443-460 ◽  
Author(s):  
Rodolfo A. Tamayo* ◽  
René C. Maury* ◽  
Graciano P. Yumul ◽  
Mireille Polvé ◽  
Joseph Cotten ◽  
...  
Keyword(s):  
Partial Melting ◽  
Subduction Zone ◽  
Volcanic Rocks ◽  
The Philippines ◽  
Island Arc ◽  
Island Arcs ◽  
Geodynamic Evolution ◽  
Wide Range ◽  
Opening And Closing ◽  
Back Arc

Abstract The basement complexes of the Philippine archipelago include at least 20 ophiolites and ophiolitic complexes. These complexes are characterised by volcanic sequences displaying geochemical compositions similar to those observed in MORB, transitional MORB-island arc tholeiites and arc volcanic rocks originating from modern Pacific-type oceans, back-arc basins and island arcs. Ocean island basalt-like rocks are rarely encountered in the volcanic sequences. The gabbros from the ophiolites contain clinopyroxenes and plagioclases showing a wide range of XMg and An values, respectively. Some of these gabbros exhibit mineral chemistries suggesting their derivation from basaltic liquids formed from mantle sources that underwent either high degrees of partial melting or several partial melting episodes. Moreover, some of the gabbros display a crystallization sequence where orthopyroxene and clinopyroxene appeared before plagioclase. The major element compositions of coexisting orthopyroxenes and olivines from the mantle peridotites are consistent with low to high degrees of partial melting. Accessory spinels in these peridotites display a wide range of XCr values as well with some of them above the empirical upper limit of 0.6 often observed in most modern mid-oceanic ridge (MOR) mantle rocks. Co-existing olivines and spinels from the peridotites also exhibit compositions suggesting that they lastly equilibrated under oxidizing mantle conditions. The juxtaposition of volcanic rocks showing affinities with modern MOR and island arc environments suggests that most of the volcanic sequences in Philippine ophiolites formed in subduction-related geodynamic settings. Similarly, their associated gabbros and peridotites display mineralogical characteristics and mineral chemistries consistent with their derivation from modern supra-subduction zone-like environments. Alternatively, these rocks could have, in part, evolved in a supra-subduction zone even though they originated from a MOR-like setting. A simplified scenario regarding the early geodynamic evolution of the Philippines is proposed on the basis of the geochemical signatures of the ophiolites, their ages of formation and the ages and origins of the oceanic basins actually bounding the archipelago, including basins presumed to be now totally consumed. This scenario envisages the early development of the archipelago to be largely dominated by the opening and closing of oceanic basins. Fragments of these basins provided the substratum on top of which the Cretaceous to Recent volcanic arcs of the Philippines were emplaced.

Weka Trainable Segmentation Plugin in ImageJ: A Semi-Automatic Tool Applied to Crystal Size Distributions of Microlites in Volcanic Rocks

2018 ◽  
Vol 24 (6) ◽  
pp. 667-675 ◽  
Author(s):  
Charline Lormand ◽  
Georg F. Zellmer ◽  
Károly Németh ◽  
Geoff Kilgour ◽  
Stuart Mead ◽  
...  
Keyword(s):  
Crystal Size ◽  
Low Cost ◽  
Volcanic Rocks ◽  
Scattered Electron ◽  
Promising Alternative ◽  
Wide Range ◽  
Segmented Images ◽  
Electron Microscopes ◽  
Automatic Tool ◽  
Magmatic History

AbstractCrystals within volcanic rocks record geochemical and textural signatures during magmatic evolution before eruption. Clues to this magmatic history can be examined using crystal size distribution (CSD) studies. The analysis of CSDs is a standard petrological tool, but laborious due to manual hand-drawing of crystal margins. The trainable Weka segmentation (TWS) plugin in ImageJ is a promising alternative. It uses machine learning and image segmentation to classify an image. We recorded back-scattered electron (BSE) images of three volcanic samples with different crystallinity (35, 50 and ≥85 vol. %), using scanning electron microscopes (SEM) of variable image resolutions, which we then tested using TWS. Crystal measurements obtained from the automatically segmented images are compared with those of the manual segmentation. Samples up to 50 vol. % crystallinity are successfully segmented using TWS. Segmentation at significantly higher crystallinities fails, as crystal boundaries cannot be distinguished. Accuracy performance tests for the TWS classifiers yield high F-scores (>0.930), hence, TWS is a successful and fast computing tool for outlining crystals from BSE images of glassy rocks. Finally, reliable CSD’s can be derived using a low-cost desktop SEM, paving the way for a wide range of research to take advantage of this new petrological method.

Nature and origin of the Triassic volcanism in Albania and Othrys: a key to understanding the Neotethys opening?

2008 ◽  
Vol 179 (4) ◽  
pp. 411-425 ◽  
Author(s):  
Philippe Monjoie ◽  
Henriette Lapierre ◽  
Artan Tashko ◽  
Georges H. Mascle ◽  
Aline Dechamp ◽  
...  
Keyword(s):  
Eastern Mediterranean ◽  
Volcanic Rocks ◽  
Island Arc ◽  
Late Triassic ◽  
Central Mediterranean ◽  
Crustal Component ◽  
Sw Turkey ◽  
Wide Range ◽  
Back Arc ◽  
Island Basalt

AbstractTriassic volcanic rocks, stratigraphically associated with pelagic or reef limestones, are tectonically juxtaposed with Mesozoic ophiolites in the Tethyan realm. From the central (Dinarides, Hellenides) and eastern Mediterranean (Antalya, Troodos, Baër Bassit) to the Semail nappes (Oman), they occur either associated to the tectonic sole of the ophiolitic nappes or as a distinct tectonic pile intercalated between the ophiolites and other underthrust units. In the Dinaro-Hellenic belt, the Pelagonian units represent the lower plate, which is underthrust beneath the ophiolites. Middle to Late Triassic volcanic sequences are interpreted as the eastern flank of the Pelagonian platform and are therefore considered as a distal, deep-water part of the Pelagonian margin.The Triassic volcanics from Albania and Othrys are made up of basaltic pillowed and massive flows, associated locally with dolerites and trachytes. New elemental, Nd and Pb isotopic data allow to recognize four types of volcanic suites: (1) intra-oceanic alkaline and tholeiitic basalts, (2) intra-oceanic arc-tholeiites, (3) back-arc basin basalts, (4) calc-alkaline mafic to felsic rocks. Nd and Pb isotopic initial ratios suggest that the within-plate volcanic rocks were derived from an enriched oceanic island basalt type mantle source, devoid of any continental crustal component. The lower εNd value of the trachyte could be due to assimilation of oceanic altered crust or sediments in a shallow magma chamber. Island arc tholeiites and back-arc basin basalts have a similar wide range of εNd. The absence of Nb negative anomalies in the back-arc basin basalts suggests that the basin floored by these basalts was wide and mature. The high Th contents of the island arc tholeiites suggest that the arc volcanoes were located not far away from the continental margin.Albania and Othrys volcanics contrast with the Late Triassic volcanism from eastern Mediterranean (SW Cyprus, SW Turkey), which displays solely features of oceanic within plate suites. The presence of back-arc basin basalts associated with arc-related volcanics in Central Mediterranean indicates that they were close to a still active subduction during the Upper Triassic, while back-arc basins developed, associated with within-plate volcanism, leading to the NeoTethys opening.

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