Lithium isotopes in kimberlites, lamproites and lamprophyres as tracers of source components and processes related to supercontinent cycles

2021 ◽  
pp. SP513-2021-60
Author(s):  
Lukáš Krmíček ◽  
Tomáš Magna ◽  
Ashutosh Pandey ◽  
N. V. Chalapathi Rao ◽  
Jindřich Kynický
Keyword(s):  
Isotope Composition ◽  
Volcanic Rocks ◽  
Dharwar Craton ◽  
Metamorphic Rocks ◽  
Eastern Dharwar Craton ◽  
Content Type ◽  
Bastar Craton ◽  
Li Isotope ◽  
Supplementary Material ◽  
Orogenic Belts

AbstractOur pilot study reveals potential fingerprints of Li isotopes recorded in the Mesoproterozoic (∼1.4-1.1 Ga) kimberlites, lamproites and lamprophyres from the Eastern Dharwar Craton and Paleocene (62 Ma) orangeite from the Bastar Craton in India. The new data are interpreted in the context of available Li isotope composition of lamproitic to lamprophyric rocks occurring in Variscan (Bohemian Massif) and Alpine-Himalayan (SW Tibet) orogenic belts formed in response to Gondwana-Pangea amalgamation and break-up. As a result of supercontinents development, kimberlites from the Eastern Dharwar Craton and ‘orangeite’ from the Bastar Craton show clear presence of a component with a heavy Li isotope signature (δ7Li up to 9.7‰) similar to an ancient altered oceanic crust, whereas the Eastern Dharwar Craton lamproites (2.3-6.3‰) and lamprophyres (3.3-6.7‰) show Li isotope signatures indicative of a dominant contribution from heterogeneous lithospheric mantle. Variscan lamprophyric to lamproitic rocks and post-collisional mantle-derived (ultra)potassic volcanic rocks from SW Tibet, i.e., rocks from the orogenic belts outside the cratonic areas, are characterized by a clear Li isotope shift towards isotopically lighter component (δ7Li as low as -9.5‰) comparable with the involvement of an evolved continental crust and high-pressure metamorphic rocks in their orogenic mantle source. Such components with isotopically light Li are strikingly missing in the source of cratonic kimberlites, lamproites and lamprophyres.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5495097

The influence of volcanic supply on the composition of modern river sands: the case study of the Ofanto river, Southern Italy

2021 ◽  
pp. SP520-2021-89
Author(s):  
Mariano Tenuta ◽  
Paola Donato ◽  
Rocco Dominici ◽  
Rosanna De Rosa
Keyword(s):  
Volcanic Rocks ◽  
Pyroclastic Deposits ◽  
Content Type ◽  
Sedimentary Deposits ◽  
History Of ◽  
Supplementary Material ◽  
High Production ◽  
Volcaniclastic Deposits ◽  
Pyroclastic Fall

AbstractThe Ofanto river drains volcanic rocks from the Monte Vulture, lacustrine-fluviolacustrine deposits associated with the same volcano and sedimentary deposits of the Southern Apennines and the Bradanic foredeep sequences. Comparing the modal composition of river sands and the outcrop area of different lithologies in the different sub-basins, an over-concentration of the volcaniclastic fraction, mainly represented by loose crystals of clinopyroxene, garnet and amphibole, is shown. This has been related to the preferential erosion of pyroclastic deposits, characterized by high production of sand-sized loose minerals, together with the carbonate lability and the low sand-sized detritus production from claystones and marls. The occurrence of volcaniclastic components upstream of Monte Vulture can be explained with a contribution from the lacustrine-fluviolacustrine deposits outcropping in the upstream sector or from pyroclastic fall deposits of Monte Vulture and/or Campanian volcanoes. This research shows that the volcanic record in the fluvial sands of the Ofanto river comes from weathering and sorting processes of volcaniclastic deposits rather than of the lavas building the main edifice. Therefore, caution must be taken during paleoenvironmental and paleoclimatic reconstructions when relating the type and abundance of the volcanic component in sediments to the weathering stage and evolutionary history of the volcano.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5643959

scholarly journals Hypozonal gold mineralisation in shear zone hosted deposits driven by fault valve action and fluid mixing: the Nalunaq deposit, Greenland

2021 ◽  
pp. SP516-2021-38
Author(s):  
Martin Smith ◽  
David Banks ◽  
Santanu Ray ◽  
Francis Bowers
Keyword(s):  
Shear Zone ◽  
Fluid Mixing ◽  
Metamorphic Rocks ◽  
Chloride Complexes ◽  
Content Type ◽  
Pressure Cycling ◽  
Seismic Slip ◽  
Vein Formation ◽  
Supplementary Material ◽  
Fault Valve

AbstractThe Nalunaq deposit, Greenland, is a hypozonal, shear zone-hosted, Au deposit. The shear zone has previously been interpreted to have undergone 4 stages of deformation, accompanied by fluid flow,and vein formation. Coupled with previous trapping T estimates, fluid inclusion data are consistent with trapping of fluids with salinities between 28-45 wt. % NaCl eq., from 300-475°C during D2 and D3, with pressure varying between ∼800 and 100Mpa. The range reflects pressure cycling during seismic slip related depressurisation events. D4 fluids were lower salinity and trapped from 200-300°C, at ∼50-200Mpa during late stage normal faulting. The variation in major element chemistry is consistent with ingress of hypersaline, granitoid equilibrated fluids into the shear zone system and mixing with fluids that had reacted with the host metamorphic rocks. D4 stage fluids represent ingress of meteoric fluids into the system. Gold contents in inclusion fluids range from ∼300-10mg/kg. These data are consistent with the high P-T solubility of Au as AuHS(H2S)30 complexes, and Au deposition by decompression and cooling. The high salinities also suggest Au transport as chloride complexes may have been possible. Gold distribution was modified by the release of chemically bound or nanoscale Au during sulphide oxidation at the D4 stage.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5635812

scholarly journals The grandest of them all: the Lomagundi-Jatuli Event and Earth's oxygenation

2021 ◽  
pp. jgs2021-036
Author(s):  
A.R. Prave ◽  
K. Kirsimäe ◽  
A. Lepland ◽  
A.E. Fallick ◽  
T. Kreitsmann ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Isotope Composition ◽  
Atmospheric Oxygen ◽  
A Priori ◽  
Content Type ◽  
Earth History ◽  
Depositional Settings ◽  
Marine Carbonate ◽  
New Ideas ◽  
Supplementary Material

The Palaeoproterozoic Lomagundi-Jatuli Event (LJE) is generally considered the largest, in both amplitude and duration, positive carbonate C-isotope (δ13Ccarb) excursion in Earth history. Conventional thinking is that it represents a global perturbation of the carbon cycle between 2.3–2.1 Ga linked directly with and in part causing the postulated rise in atmospheric oxygen during the Great Oxidation Event. In addition to new high-resolution δ13Ccarb measurements from LJE-bearing successions of NW Russia, we compiled 14,943 δ13Ccarb values obtained from marine carbonate rocks 3.0–1.0 Ga in age and from selected Phanerozoic time intervals as a comparator of the LJE. Those data integrated with sedimentology show that, contra to consensus, the δ13Ccarb trend of the LJE is facies (i.e. palaeoenvironment) dependent. Throughout the LJE interval, the C-isotope composition of open and deeper marine settings maintained a mean δ13Ccarb value of +1.5 ± 2.4‰, a value comparable to those settings for most of Earth history. In contrast, the 13C-rich values that are the hallmark of the LJE are limited largely to nearshore-marine and coastal-evaporitic settings with mean δ13Ccarb values of +6.2 ± 2.0‰ and +8.1 ± 3.8‰, respectively. Our findings confirm that changes in δ13Ccarb are linked directly to facies changes and archive contemporaneous DIC pools having variable C-isotopic compositions in laterally adjacent depositional settings. The implications are that the LJE cannot be construed a priori as representative of the global carbon cycle or a planetary-scale disturbance to that cycle, nor as direct evidence for oxygenation of the ocean-atmosphere system. This requires rethinking models relying on those concepts and framing new ideas in the search for understanding the genesis of the grandest of all positive C-isotope excursions, its timing and its hypothesised linkage to oxygenation of the atmosphere.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5471815

Three-phased Middle Permian–Mesozoic magmatism in the Great Xing'an Range: implications for episodic southern subduction of the Mongol-Okhotsk ocean

2021 ◽  
pp. jgs2020-152
Author(s):  
Fei Yang ◽  
Yinglei Li ◽  
Guang Wu ◽  
Huichuan Liu ◽  
Gongzheng Chen ◽  
...  
Keyword(s):  
Partial Melting ◽  
Early Cretaceous ◽  
Active Continental Margin ◽  
Volcanic Rocks ◽  
Middle Permian ◽  
Content Type ◽  
Supplementary Material ◽  
Mesozoic Magmatism ◽  
Erguna Massif ◽  
Great Xing’An Range

The Erguna Massif is located in the southwestern portion of the Great Xing'an Range and is adjacent to the Mongol–Okhotsk suture zone. It has not to be determined whether the tectonic evolutionary processes of the Erguna Massif belong to the Mongol–Okhotsk tectonic regime during the Middle Permian–Mesozoic. In this study, a suite of rocks comprising Mesozoic S-type monzogranite (LA–ICP–MS U–Pb zircon age of 248 ± 1.2 Ma), highly fractionated I-type rhyolite (204 ± 1.1 Ma), gabbro (196 ± 1.9 Ma), A2-type volcanic rocks (190 ± 0.9 Ma), A1-type trachydacite (167 ± 0.8 Ma), and Early Cretaceous A1-type alkaline rhyolite are newly identified and geochemically studied. The rhyolite, gabbro, trachydacite, and alkaline rhyolite whole-rock Sr–Nd isotope analyses got the values of initial 87Sr/86Sr ratios ranging from 0.7044 to 0.7058 and εNd(t) values of −0.68–+2.73. These samples show εHf(t) values ranging from +5.3 to +11.2 and TDM2 ranging from 0.48 Ga to 0.90 Ga. The 248 Ma monzogranites were produced by the partial melting of greywackes. The 204 Ma rhyolites were derived from the partial melting of lower mafic crust. The 196 Ma gabbros originated from the partial melting of an enriched mantle metasomatized by subduction-slab released fluids. The 190 Ma volcanic rocks, 167 Ma trachydacite, and Early Cretaceous alkaline rhyolite were mainly formed by the partial melting of the basaltic rocks. They all show enrichment in the large ion lithophile elements (e.g., Rb, Ba, and K) and depletions in the high field strength elements (e.g., Nb, Ta, and Ti), suggesting they formed in an active continental margin setting. The features of these igneous rocks indicate the southward subduction of the Mongol-Okhotsk ocean plate. Based on compiled age data, three phases of middle Mesozoic magmatism were identified in the Erguna Massif at ca. 275–225 Ma, 215–165 Ma, and 150–110 Ma. In addition, three similar magmatic phases were found in the Xing'an Massif. However, a hysteresis about ca. 15–20 Ma exists between the two massifs. These magmatic rocks may record the three stages of the southward subduction of the Mongol–Okhotsk oceanic plate, and two periods of slab rollback occurred during the Middle Permian to Early Cretaceous.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5459285

scholarly journals Modern Concepts on Diamond Genesis

2021 ◽  
Vol 59 (11) ◽  
pp. 1038-1051
Author(s):  
F. V. Kaminsky ◽  
S. A. Voropaev
Keyword(s):  
Surface Tension ◽  
Surface Energy ◽  
Physical Properties ◽  
Trace Element ◽  
Thermodynamic Parameters ◽  
Isotope Composition ◽  
Volcanic Rocks ◽  
Metamorphic Rocks ◽  
Diamond Genesis

AbstractThe best-known, most well-studied diamondiferous rocks are kimberlites and lamproites. Diamonds are also found in impactites, metamorphic rocks, ophiolites, and modern volcanic rocks. Diamonds from these rocks differ from kimberlitic diamonds in size, morphology, trace-element and isotope composition, and physical properties. Differences in these characteristics are related to their different mechanisms of origin. In some cases, diamonds can be formed in “metastable” conditions under disequilibrium thermodynamic parameters, supporting the conclusion that diamond is a polygenetic mineral, formed in nature under different physicochemical and geodynamic conditions. According to thermodynamic considerations and calculations, “metastable” crystallization of diamond is mainly controlled by the size of the forming crystallites. The main effectors in decreasing the energetic barrier for nanosized diamonds are surface tension and related surface energy.

Late Permian ultrapotassic rhyolites in SE Thailand: Evidence for a Paleotethyan continental rift basin

2021 ◽  
pp. jgs2021-079
Author(s):  
Xin Qian ◽  
Shen Ma ◽  
Xianghong Lu ◽  
Sainan Wu ◽  
Mongkol Udchachon ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Continental Rift ◽  
Late Permian ◽  
Rift Basins ◽  
Content Type ◽  
Metasedimentary Rocks ◽  
High K ◽  
Supplementary Material ◽  
Group 2 ◽  
T Values

Volcanic rocks in the Chanthaburi zone are rarely reported and important for investigating the tectonic evolution of Paleotethyan Ocean in SE Thailand. Four rhyolitic samples from the Ko Chang Island yield zircon ages of 254–258 Ma, confirming the presence of Late Permian volcanic rocks in SE Thailand. These rocks consist of Group 1 rhyolites and Group 2 rhyolitic ignimbrites and have high K2O contents of 4.92–7.10 wt.% and A/CNK values of 1.10–1.69. They are enriched in LREEs, Rb, Th, U, Zr and Y, and show negative anomalies of Ba, Sr, Nb, Ta and Ti with obvious Eu anomalies. Their whole-rock εNd (t) values range from −1.7 to −3.1. Zircon in-situ εHf (t) and δ18O values range from 0.0 to +5.6 and 8.2‰ to 9.6‰, respectively. They belong to peraluminous, ultrapotassic A-type rhyolites, and were derived from partial melting of a mixed source of Mesoproterozoic metasedimentary rocks with a component of juvenile mafic crust. These ultrapotassic rhyolites formed in a continental rift setting in response to the rollback of subducted Paleotethyan oceanic slab beneath the Indochina Block. Combining previous geological observations, we propose that there are some sporadically distributed continental rift basins along the Eastern Paleotethyan domain during the Permian.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5635390

Eruption history, petrogeochemistry, and geodynamic background of Tengchong volcanoes in Yunnan Province, SW China

2020 ◽  
pp. SP510-2020-45
Author(s):  
Hongmei Yu ◽  
Bo Zhao ◽  
Zhengquan Chen ◽  
Haiquan Wei ◽  
Wenjian Yang ◽  
...  
Keyword(s):  
Yunnan Province ◽  
Volcanic Rocks ◽  
Evolutionary Process ◽  
Source Area ◽  
Volcanic Field ◽  
Indian Plate ◽  
Eurasian Plate ◽  
Content Type ◽  
Supplementary Material ◽  
Eruption History

AbstractThe Tengchong Volcanic Field (TVF) is one of the youngest volcanic areas in China, and located in the southwestern part of Yunnan Province, China, adjacent to the collision zone between the Indian Plate and Eurasian Plate. This paper summarizes the results of previous research on the eruption history, petrochemistry, and geodynamic background of the TVF and presents a detailed analysis of the available data. Eruptions took place from the Pliocene to the Holocene and were divided into five stages. The composition of the magma went through two cycles: the N2-Q1 P-Q2 P volcanic rocks went through the evolutionary process from basalt to dacite and the Q3 P-Qh magma evolved from trachybasalt to trachyte. The evolution of magma is mainly related to the crystallisation and separation of pyroxene and ilmenite. The mantle source area of the TVF volcanic rocks was caused by the mixing between the MORB-source mantle and the eastern Indian continental margin sediments (EIS) to different degree. Geophysical data also showed that the Indian Plate has been subducted under the TVF area. There are also magma chambers in the crust within a depth of 25 km in the TVF that are replenished by mantle magma.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5227663

Nd isotope record of ocean closure archived in limestones of the Devonian–Carboniferous carbonate platform, Greater Karatau, southern Kazakhstan

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-077 ◽  
Author(s):  
Z. Belka ◽  
J. Dopieralska ◽  
M. Jakubowicz ◽  
S. Skompski ◽  
A. Walczak ◽  
...  
Keyword(s):  
Carbonate Platform ◽  
Isotope Composition ◽  
Concentration Data ◽  
Nd Isotope ◽  
Content Type ◽  
Wide Range ◽  
Volcanic Events ◽  
Isotope Record ◽  
Supplementary Material ◽  
T Values

The neodymium isotope composition of micritic limestones from the Devonian–Carboniferous carbonate platform of the Greater Karatau (southern Kazakhstan) was investigated to test the ability of calcite micrite to archive Nd isotope signatures of seawater. The carbonate fraction that displays seawater-like rare earth element (REE + Y) signatures is often more radiogenic than the dispersed terrigenous material in the samples. Hence, its Nd isotope composition is interpreted to correspond to the seawater from which the micrite was precipitated. The seawater on the Karatau platform exhibited an extremely wide range of εNd(t) values from –9.3 to +4.3 (the most radiogenic value measured for past seawater to date) and very uniform Sm/Nd ratios, from 0.19 to 0.22, lying within the range characteristic for modern oceanic water. The temporal trend in εNd(t) values is interpreted to document the final closure of the Uralian–Turkestan Ocean. It shows that the subduction along Kazakhstan's active margin had already started at the beginning of the Tournaisian (c. 355 Ma), at least 23 Myr earlier than previously thought. The application of Nd isotope time series on biostratigraphically dated carbonates opens a new direction for geotectonic studies. This approach has the potential to provide useful constraints for the precise dating of the duration of geotectonic and volcanic events.Supplementary material: Nd isotope and REE concentration data, summary of stratigraphic and lithological data, field photographs and additional geochemical plots are available at: https://doi.org/10.6084/m9.figshare.c.5110163

The waste rock of the Touro copper deposit in Galicia, Spain: challenges for its environmental characterization

2021 ◽  
pp. geochem2020-081
Author(s):  
Tom Meuzelaar ◽  
Pablo Núñez-Fernández ◽  
Agustín Martín-Izard ◽  
Daniel Arias-Prieto ◽  
Fernando Díaz-Riopa
Keyword(s):  
Sulfide Oxidation ◽  
Environmental Issues ◽  
Metamorphic Rocks ◽  
Acid Rock ◽  
Neutralization Potential ◽  
Content Type ◽  
Oxidation Rates ◽  
Ph Values ◽  
Link Type ◽  
Supplementary Material

Characterization of metamorphic rocks to evaluate waste material acid rock drainage potential is particularly challenging as commonly used laboratory methods can result in significant under-prediction of ARD potential. Static tests were conducted for over 300 samples from the Touro copper project and indicate that carbon-based methods frequently overestimate acid neutralization potential due to the presence of both graphite and manganese-iron carbonates. The Modified Sobek method more accurately accounts for the buffering capacity of carbonates and does not account for graphite, although aluminosilicate dissolution kinetics need to be evaluated in the context of sulfide oxidation rates. Historic sulfur assays for the project relied on methods insufficient to fully digest metamorphosed sulfides and required correction. The more aggressive Leco sulfur method provides accurate sulfur estimates and has been adopted for the project going forward.Static test metrics such as the Net Neutralization Potential or Neutralization Potential Ratio, therefore, can give misleading results when incorrect characterization methods are employed. Such metrics should be considered as screening level, used with caution, and complemented with careful field and laboratory kinetic tests. Preliminary humidity cell testing of five Touro samples suggests that terminal pH values for cells that have become acidic closely match predicted NAG pH values. The NAG pH test avoids some of the challenges associated with sulfur and carbon predictions in metamorphic rocks as it directly buffers sulfide oxidation acidity with available material neutralization potential. As such, NAG pH has been adopted as the accepted project metric for segregating acid-generating from non-acid-generating waste.Thematic collection: This article is part of the Hydrochemistry related to exploration and environmental issues collection available at: https://www.lyellcollection.org/cc/hydrochemistry-related-to-exploration-and-environmental-issuesSupplementary material:https://doi.org/10.6084/m9.figshare.c.5389948

Volcanic geology and petrochemistry of Ashikule volcanic field in western Kunlun mountains of Tibetan plateau

2020 ◽  
pp. SP510-2020-133
Author(s):  
Jiandong Xu ◽  
Bo Zhao ◽  
Hongmei Yu ◽  
Feixiang Wei ◽  
Zhengquan Chen
Keyword(s):  
Tibetan Plateau ◽  
Volcanic Rocks ◽  
Volcanic Field ◽  
Field Investigation ◽  
Content Type ◽  
Kunlun Mountains ◽  
Northern Tibetan Plateau ◽  
Western Kunlun ◽  
Geologic Map ◽  
Supplementary Material

AbstractAshikule volcanic field, developed in the western Kunlun mountain of north Tibet, is composed with about 10 volcanoes, and covers a total area of about 200km2 at the average altitude around 5,000m, one of the highest volcanic field in the world. In this study, we conducted detailed field investigation of geological and geomorphological features of volcanic rocks and volcanic edifices in Ashikule basin, and compiled large-scaled geologic map of the study area for the first time. We also collected series of samples to conduct petrochemistry analysis, as well as high-precision 40Ar/39Ar geochronology study of selected lavas from Ashikule volcanic field. Finally, we refined the eruption history for the volcanic activity in the basin, which provides some new volcanological evidence for the study of tectonic evolution of the Northern Tibetan Plateau.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5227665

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