scholarly journals Triassic trachytic volcanism in the Bangong–Nujiang Ocean: geochemical and geochronological constraints on a continental rifting event

2021 ◽  
pp. 1-16
Author(s):  
Ming Zheng ◽  
Yang Song ◽  
Haifeng Li ◽  
Carl Guilmette ◽  
Juxing Tang ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Continental Rift ◽  
Geochemical Data ◽  
Rift System ◽  
Inductively Coupled ◽  
Palaeomagnetic Data ◽  
High K ◽  
African Rift ◽  
Geochronological Constraints ◽  
Qiangtang Terrane

Abstract The Bangong–Nujiang suture zone (BNSZ), which separates the Gondwana-derived Qiangtang and Lhasa terranes, preserves limited geological records of the Bangong–Nujiang Ocean (BNO). The timing of opening of this ocean has been hotly debated due to the rare and complicated rock records in the suture zones, which span over 100 Ma from Carboniferous–Permian to Early Jurassic time, based on geological, palaeontological and palaeomagnetic data. A combination of geochemical, geochronological and isotopic data are reported for the Riasairi trachytes, central BNSZ, northern Tibet, to constrain its petrogenesis and tectonic settings. Zircon U–Pb dating by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) yields mean ages of 236 Ma. Geochemically, these rocks are high-K calc-alkaline with moderate SiO2 (59.1–67.5 wt%) and high K2O + Na2O (8.1–11.6 wt%) contents. They are enriched in light rare earth elements with negative Eu anomalies, and show enrichments in high-field-strength elements with positive ‘Nb, Ta’ anomalies, similar to the intra-continental rift setting-related felsic lavas from the African Rift System. The high positive zircon ϵHf(t) and bulk ϵNd(t) values, as well as high initial Pb isotopes, imply a heterogeneous source involving both asthenospheric and subcontinental lithospheric mantle. The field and geochemical data jointly suggest that the Riasairi trachytes within the Mugagangri Group were formed in a continental rift setting. We interpret that the continental-rift-related Riaisairi trachytic lavas as derived from the southern margin of the Qiangtang terrane, implying that the BNO would have opened by Middle Triassic time, well after the commonly interpreted break-up of the Qiangtang terrane from Gondwana.

Mapping Magmatic and Hydrothermal Processes from Routine Exploration Geochemical Analyses

2020 ◽  
Vol 115 (3) ◽  
pp. 489-503 ◽  
Author(s):  
Scott Halley
Keyword(s):  
Inductively Coupled Plasma ◽  
Mining Industry ◽  
Analysis Data ◽  
Ore Deposits ◽  
Mineral Deposits ◽  
Geochemical Data ◽  
High Quality ◽  
Inductively Coupled ◽  
Hydrothermal Processes ◽  
Geochemical Analyses

Abstract Analytical methods used by commercial assay laboratories have improved enormously in recent years. Inductively coupled plasma-atomic emission spectroscopy and inductively coupled plasma-mass spectrometry methods now report analyses for half of the periodic table with exceptional detection limits and precision. It is becoming commonplace for mining companies to use such methods routinely for the analysis of drill samples throughout mineral deposits. Improvements in software and computing power now allow rapid interrogation of upward of 100,000 assay samples. Geochemical analyses are quantitative, are independent of observer bias, and can form the basis for robust geologic and mineralogical models of mineral deposits, as well as shed light on scientific questions. In particular, consistently collected, high-quality geochemical analyses can significantly improve and systematize logging of lithological and hydrothermal alteration mineralogic changes within drill core. In addition, abundant, high-quality geochemical data provide insights into magmatic and hydrothermal processes that were previously difficult to recognize and that have obvious applications to mineral exploration and improved genetic models of ore deposits. This paper describes a workflow that mining industry geologists can apply to their multielement analysis data to extract more information about magma compositions and gangue mineralogy.

scholarly journals Ore Mineralogy, Trace Element Geochemistry and Geochronological Constraints at the Mollehuaca and San Juan de Chorunga Au-Ag Vein Deposits in the Nazca-Ocoña Metallogenic Belt, Arequipa, Peru

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1112
Author(s):  
Jorge Crespo ◽  
Elizabeth Holley ◽  
Katharina Pfaff ◽  
Madeleine Guillen ◽  
Roberto Huamani
Keyword(s):  
Inductively Coupled Plasma ◽  
Geological Mapping ◽  
Small Scale ◽  
Trace Element Geochemistry ◽  
San Juan ◽  
Element Geochemistry ◽  
Gold Mines ◽  
Inductively Coupled ◽  
Metallogenic Belt ◽  
Geochronological Constraints

The Mollehuaca and San Juan de Chorunga deposits are hosted in the poorly explored gold and copper trends of the Nazca-Ocoña metallogenic belt in Arequipa, Perú, which extends from Trujillo (9 °S) to Nazca-Ocoña (14 °S). The aim of this study is to characterize the age, occurrence, and distribution of quartz vein-hosted Au-Ag mineralization and associated trace elements (e.g., Hg, Pb, Cu, Zn, and Bi) in these deposits. Here, we present geological mapping, geochemical whole rock inductively coupled plasma (ICP)-MS data of the veins, petrographic observations, backscattered electron images, quantitative SEM-based automated mineralogy, and electron microprobe analyses (EMPA). Despite the fact that there are numerous small-scale gold mines in the Nazca-Ocoña metallogenic belt, there have been few studies that document the origin and geological evolution of these deposits or the implications for decision-making in exploration, metallurgical processing, and environmental management. In this research, we document the host rock age of the mineralized veins (129.2 ± 1.0 Ma; U-Pb in zircon), the mineralization age (95.86 ± 0.05 Ma; 40Ar/39Ar in secondary biotite), the occurrence and distribution of Au-Ag in the veins, the mineral zonation present in the vein system, and the zircon geochemistry, in order to provide tools for natural resource management in the metallogenic belt.

A geochemical record of late Holocene palaeoenvironmental changes at King George Island (maritime Antarctica)

2011 ◽  
Vol 23 (3) ◽  
pp. 255-267 ◽  
Author(s):  
Patrick Monien ◽  
Bernhard Schnetger ◽  
Hans-Jürgen Brumsack ◽  
H. Christian Hass ◽  
Gerhard Kuhn
Keyword(s):  
Inductively Coupled Plasma ◽  
Chemical Weathering ◽  
Radiometric Dating ◽  
Ice Age ◽  
Geochemical Data ◽  
King George Island ◽  
Overlying Water ◽  
Inductively Coupled ◽  
Bulk Parameters ◽  
Maxwell Bay

AbstractDuring RV Polarstern cruise ANT-XXIII/4 in 2006, a gravity core (PS 69/335-2) and a giant box core (PS 69/335-1) were retrieved from Maxwell Bay off King George Island (KGI). Comprehensive geochemical (bulk parameters, quantitative XRF, Inductively Coupled Plasma Mass Spectrometry) and radiometric dating analyses (14C, 210Pb) were performed on both cores. A comparison with geochemical data from local bedrock demonstrates a mostly detrital origin for the sediments, but also points to an overprint from changing bioproductivity in the overlying water column in addition to early diagenetic processes. Furthermore, ten tephra layers that were most probably derived from volcanic activity on Deception Island were identified. Variations in the vertical distribution of selected elements in Maxwell Bay sediments further indicate a shift in source rock provenance as a result of changing glacier extents during the past c. 1750 years that may be linked to the Little Ice Age and the Medieval Warm Period. Whereas no evidence for a significant increase in chemical weathering rates was found, 210Pb data revealed that mass accumulation rates in Maxwell Bay have almost tripled since the 1940s (0.66 g cm-2 yr-1 in ad 2006), which is probably linked to rapid glacier retreat in this region due to recent warming.

scholarly journals Rare Earth Elements Assessment in the Granitoids of Part of Southwestern Nigeria

2020 ◽  
Vol 1 (5) ◽  
Author(s):  
Victoria B. Omotunde ◽  
Akinade S. Olatunji ◽  
Maryam O. Abdus-Salam
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Inductively Coupled Plasma ◽  
Granite Gneiss ◽  
Biotite Granite ◽  
Geochemical Data ◽  
Southwestern Nigeria ◽  
Lithological Mapping ◽  
Inductively Coupled ◽  
Gneiss Granite

The Rare Earth Elements (REE) composition of granitoids in and around Ila-Orangun area Southwestern Nigeria was assessed in order to ascertain their potential for possible exploitation. Detailed lithological mapping of the area was undertaken followed by whole rock geochemical analysis of representative samples of the granitoids using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) technique. Petrographic study of the samples was carried out as well as the interpretation of the geochemical data using diverse geochemical discrimination plots. The rock units mapped were biotite granite gneiss, granite gneiss and hornblende biotite granite. Biotite hornblende gneiss, quartzite, talc-chlorite-tremolite-schist, mica schist and pegmatites were the surrounding country rocks. The REE concentrations (in ppm) revealed higher concentrations of the light REEs compared to the heavy REEs. The fractionation ratio, (La/Yb)N ranged from 4.35-15.04 (granite gneiss) and 13.78-18.48 (hornblende biotite granite) indicating enrichment in LREEs over the HREEs. The spider plot for the REEs also showed that the granitoids are LREE-enriched and HREE-depleted suggesting fractional crystallisation and a distinct negative Eu anomaly indicating plagioclase fractionation. Enrichment plot also revealed that the REEs in the granitoids are significantly enriched. Comparison with other areas showed that the granitoids of the study area especially the hornblende biotite granite has higher concentrations of REEs and may be a possible pointer of REE mineralisation.

Petrogenesis of early Permian granitic dykes in the Wulanhuduge area, central Inner Mongolia, North China: constraints from geochronology, geochemistry, and Sr–Nd–Pb isotopes

2020 ◽  
Vol 57 (6) ◽  
pp. 747-764 ◽  
Author(s):  
Xiang-xin Zhang ◽  
Yong-feng Gao ◽  
Shi-he Lei
Keyword(s):  
Inner Mongolia ◽  
Inductively Coupled Plasma ◽  
North China ◽  
Granite Porphyry ◽  
Pb Isotopes ◽  
Geochemical Data ◽  
Early Permian ◽  
Inductively Coupled ◽  
Slab Breakoff ◽  
End Stage

Early Permian granitic dykes are well developed in the Wulanhuduge area, central Inner Mongolia, North China. In this study, we investigated the petrography, geochronology, and whole-rock geochemistry of the granite porphyry dykes in the Wulanhuduge area. Laser ablation inductively coupled plasma mass spectrometry zircon U–Pb dating yielded 206Pb/238U ages of 289–288 Ma for these granite porphyry dykes, indicating they were emplaced in the early Permian. These granitic dykes are high in silica and alkali contents, and low in total Fe2O3, MgO, CaO, and P2O5 contents. They show enrichment in large-ion lithophile elements such as Rb, Ba, Th, U and K, and depletion in high field strength elements such as Nb, Ta, and Ti, typical of arc-like magma. Their Sr–Nd–Pb isotopic compositions indicate low initial 87Sr/86Sr ratios (0.70306–0.70564), positive εNd(t) values (+3.3 to +3.9), and radiogenic Pb isotopes with (206Pb/204Pb)i of 18.080–18.616, (207Pb/204Pb)i of 15.497–15.555, and (208Pb/204Pb)i of 37.713–38.175. These geochemical data, along with petrological characteristics, suggest that they belong to high K calc-alkaline I-type granites and were generated by the partial melting of the mafic rocks from the pre-existing juvenile arc crust in a post-subduction extensional setting caused by slab breakoff. Therefore, the emplacement of these granite porphyry dykes in the Wulanhuduge area may represent the end stage of the subduction–accretion process in central Inner Mongolia.

scholarly journals Petrographical and Geochemical Characteristics of Magmatic Rocks in the Northwestern Siberian Traps Province, Kulyumber River Valley. Part II: Rocks of the Kulyumber Site

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 415
Author(s):  
Nadezhda Krivolutskaya ◽  
Boris Belyatsky ◽  
Bronislav Gongalsky ◽  
Alexander Dolgal ◽  
Andrey Lapkovsky ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Element Distribution ◽  
River Valley ◽  
Geochemical Data ◽  
Trace Element Distribution ◽  
Mafic Rocks ◽  
Inductively Coupled ◽  
Magmatic Rocks ◽  
Magma Sources ◽  
Siberian Trap

The origin of the Siberian trap province is under discussion even though numerous models of its formation have been created over the last three decades. This situation is mainly due to lack of modern geochemical data on magmatic rocks around the province. These data are a very important tool to reconstruct of magmatic evolution within the province in time and space and to understand a mechanism of province formation. Geochemical study has only been carried out so far for the Norilsk and Meimecha–Kotuy areas. For the first time, we have studied the geochemical and mineralogical characteristics of magmatic rocks at the Kulyumber river valley located 150 km to south from the Norilsk ore district, in the junction of the Tunguska syneclise and Norilsk–Igarka zone. It comprises three sites, i.e., Khalil, Kaya, and Kulyumber. The geochemical data on the magmatic rocks of the Khalil and Kaya sites were published earlier (Part I). This article (Part II) regards geochemical and mineralogical data on igneous rocks at the Kulyumber site. Seventeen intrusive bodies (41 samples) and six samples of sedimentary rocks were studied by X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). Isotopes analyses (Sr, Nd, Pb) were conducted for 12 samples. These data were compared with data for intrusions of the Norilsk area, the Dzhaltulsky massif, Kureyka river, and intrusions in Angara river valley published earlier. The whole list of analyses includes 102 items. Three groups of intrusive rocks were recognized: (1) Mafic rocks with elevated K2O without negative Ta-Nb and Pb-positive anomalies, with (Gd/Yb)n = 2.0 and εNd = −1.0; attributed to a new Kulyumbinsky complex; (2) subalkaline rocks with elevated SiO2,TiO2, P2O5, and K2O with small negative Ta-Nb and positive Pb anomalies and (Gd/Yb)n = 1.8, εNd = −3.8; Ergalakhsky complex; and (3) mafic rocks with strong Ta-Nb and Pb anomalies and (Gd/Yb)n = 1.2–1.4, εNd = +0.4–+2.2. The third group is rather nonhomogeneous and includes intrusions of the Norilsk, Kuryesky, Katangsky, Ogonersky, and Daldykansky complexes differing in MgO content and trace element distribution (values of Ta-Nb, Pb, and Sr anomalies). Three groups of intrusive bodies had different magma sources and different condition of crystallization reflecting their origin in rift and platform regimes.

scholarly journals Mantle-Derived Corundum-Bearing Felsic Dykes May Survive Only within the Lower (Refractory/Inert) Crust: Evidence from Zircon Geochemistry and Geochronology (Ivrea–Verbano Zone, Southern Alps, Italy)

Geosciences ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 281
Author(s):  
Mattia Bonazzi ◽  
Antonio Langone ◽  
Simone Tumiati ◽  
Edoardo Dellarole ◽  
Maurizio Mazzucchelli ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Crustal Contamination ◽  
Southern Alps ◽  
Geochemical Data ◽  
Accessory Mineral ◽  
Alkaline Magmatism ◽  
Crustal Rocks ◽  
Inductively Coupled ◽  
Mafic Intrusives ◽  
Nw Italy

Corundum-rich (up to 55 vol.%) felsic dykes formed with albite, ±K-feldspar, ±hercynite and ±biotite-siderophyllite cut the lower crustal rocks exposed in the Ivrea–Verbano Zone (NW Italy). Zircon is an abundant accessory mineral and its investigation through laser ablation-inductively coupled plasma (multi-collector)-mass spectrometer (LA-ICP-(MC)MS) has allowed results to directly constrain the timing of emplacement, as well as petrology and geochemistry of parental melts. Zircons are characterized by very large concentration in rare earth elements (REE), Th, U, Nb and Ta, and negative Eu anomaly. U–Pb analysis points to Norian emplacement ages (223 ± 7 Ma and 224 ± 6 Ma), whereas large positive εHf(t) values (+13 on average) indicate a derivation from depleted to mildly enriched mantle source. The mantle signature and the corundum oversaturation were preserved thanks to limited crustal contamination of the host, high-temperature refractory granulites and mafic intrusives. According to the geochemical data and to the evidence of the development of violent explosions into the conduits, it is proposed that dykes segregated from peraluminous melts produced by exsolution processes affecting volatile-rich differentiates during alkaline magmatism. This work provides robust evidence about the transition of the geochemical affinity of Southern Alps magmatism from orogenic-like to anorogenic during Norian time, linked to a regional uprising of the asthenosphere and change of tectonic regime.

New geological model of the Lagoa Real uraniferous albitites from Bahia (Brazil)

2013 ◽  
Vol 5 (3) ◽  
Author(s):  
Alexandre Oliveira Chaves
Keyword(s):  
Inductively Coupled Plasma ◽  
Melt Inclusions ◽  
Shear Zones ◽  
Mineral Chemistry ◽  
Granitic Rocks ◽  
Geochemical Data ◽  
Magmatic Differentiation ◽  
Inductively Coupled ◽  
Icp Ms ◽  
Brasiliano Orogeny

AbstractNew evidence supported by petrography (including mineral chemistry), lithogeochemistry, U-Pb geochronology by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), and physicochemical study of fluid and melt inclusions by LA-ICP-MS and microthermometry, point to an orogenic setting of Lagoa Real (Bahia-Brazil) involving uraniferous mineralization. Unlike the previous models in which uraniferous albitites represent Na-metasomatised 1.75 Ga anorogenic granitic rocks, it is understood here that they correspond to metamorphosed sodium-rich and quartz-free 1.9 Ga late-orogenic syenitic rocks (Na-metasyenites). These syenitic rocks are rich not only in albite, but also in U-rich titanite (source of uranium). The interpretation of geochemical data points to a petrogenetic connection between alkali-diorite (local amphibolite protolith) and sodic syenite by fractional crystallization through a transalkaline series. This magmatic differentiation occurred either before or during shear processes, which in turn led to albitite and amphibolite formation. The metamorphic reactions, which include intense recrystallization of magmatic minerals, led uraninite to precipitate at 1.87 Ga under Oxidation/Reduction control. A second population of uraninites was also generated by the reactivation of shear zones during the 0.6 Ga Brasiliano Orogeny. The geotectonic implications include the importance of the Orosirian event in the Paramirim Block during paleoproterozoic Săo Francisco Craton edification and the influence of the Brasiliano event in the Paramirim Block during the West-Gondwana assembly processes. The regional microcline-gneiss, whose protolith is a 2.0 Ga syn-collisional potassic granite, represents the albitite host rock. The microcilne-gneiss has no petrogenetic association to the syenite (albitite protolith) in magmatic evolutionary terms.

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