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  • 1
    Online Resource
    Online Resource
    Berlin, Heidelberg :Springer Berlin / Heidelberg,
    Keywords: Gold ores-China-Hebei Sheng. ; Electronic books.
    Description / Table of Contents: Examples from Hebei Province, NE China.
    Type of Medium: Online Resource
    Pages: 1 online resource (210 pages)
    Edition: 1st ed.
    ISBN: 9783642773501
    Language: English
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  • 2
    In: Journal of South American earth sciences, Amsterdam [u.a.] : Elsevier Science, 1988, 26(2008), 1, Seite 1-15, 0895-9811
    In: volume:26
    In: year:2008
    In: number:1
    In: pages:1-15
    Description / Table of Contents: Late Cenozoic back-arc mafic volcanism in the southern Puna plateau of Argentina offers insights into the state of the mantle under the world's second largest continental plateau. Previous studies of the mafic magmas in this region proposed a scenario of mantle melting due to lithospheric delamination and/or steepening of the subducting slab. However, few of the centers have been precisely dated, which limits any geodynamic interpretation. We present results of laser incremental-heating 40Ar/39Ar dating of 22 back-arc centers in the southern Puna, with emphasis on the Salar de Antofalla region where volcanic activity was most intense. Three localities yielded ages between 7.3 and 7.0 Ma which, along with 2 previous 7 Ma ages, firmly establishes that back-arc activity began as early as late Miocene. Volcanism continued through the Pleistocene but the peak was in the early Pliocene. This result has important tectonic implications. If, as previously suggested, magma genesis is related to lithospheric delamination, this process was underway by the latest Miocene in the southern Puna. Furthermore, since the mafic back-arc volcanism is considered to mark a change in fault kinematics from compressional to transtensional, the new age constraints indicate that this change took place in the early Pliocene. The spatial and age distributions of the mafic centers indicate that magmatism began, and remained focussed in, a region between Salar de Antofalla and Cerro Galán. This concentration is probably structurally controlled, as it corresponds to the intersection of the NW-SE striking Archibarca lineament zone and the sets of NNE-SSW faults that run parallel to the Salar de Antofalla basin.
    Type of Medium: Online Resource
    Pages: graph. Darst
    ISSN: 0895-9811
    Language: English
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  • 3
    Publication Date: 2011-02-01
    Description: Tourmaline is a widespread mineral in the Mesoproterozoic Blackbird Co-Cu-Au-Bi-Y-REE district, Idaho, where it occurs in both mineralized zones and wallrocks. We report here major-element and B-isotope compositions of tourmaline from stratabound sulfide deposits and their metasedimentary wallrocks, from mineralized and barren pipes of tourmaline breccia, from late barren quartz veins, and from Mesoproterozoic granite. The tourmalines are aluminous, intermediate in the schorl-dravite series, with Fe/(Fe + Mg) values of 0.30 to 0.85, and 10 to 50% X-site vacancies. Compositional zoning is prominent only in tourmaline from breccias and quartz veins; crystal rims are enriched in Mg, Ca and Ti, and depleted in Fe and Al relative to cores. The chemical composition of tourmaline does not correlate with the presence or absence of mineralization. The {delta}11B values fall into two groups. Isotopically light tourmaline (-21.7 to -7.6{per thousand}) occurs in unmineralized samples from wallrocks, late quartz veins and Mesoproterozoic granite, whereas heavy tourmaline (-6.9 to +3.2{per thousand}) is spatially associated with mineralization (stratabound and breccia-hosted), and is also found in barren breccia. At an inferred temperature of 300{degrees}C, boron in the hydrothermal fluid associated with mineralization had {delta}11B values of -3 to +7{per thousand}. The high end of this range indicates a marine source of the boron. A likely scenario involves leaching of boron principally from marine carbonate beds or B-bearing evaporites in Mesoproterozoic strata of the region. The {delta}11B values of the isotopically light tourmaline in the sulfide deposits are attributed to recrystallization during Cretaceous metamorphism, superimposed on a light boron component derived from footwall siliciclastic sediments (e.g., marine clays) during Mesoproterozoic mineralization, and possibly a minor component of light boron from a magmatic-hydrothermal fluid. The metal association of Bi-Be-Y-REE in the Blackbird ores suggests some magmatic input, but involvement of granite-derived fluids cannot be conclusively established from the present database.
    Print ISSN: 0008-4476
    Topics: Geosciences
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  • 4
    Publication Date: 2019-09-23
    Description: Late Cenozoic back-arc mafic volcanism in the southern Puna plateau of Argentina offers insights into the state of the mantle under the world’s second largest continental plateau. Previous studies of the mafic magmas in this region proposed a scenario of mantle melting due to lithospheric delamination and/or steepening of the subducting slab. However, few of the centers have been precisely dated, which limits any geodynamic interpretation. We present results of laser incremental-heating 40Ar/39Ar dating of 22 back-arc centers in the southern Puna, with emphasis on the Salar de Antofalla region where volcanic activity was most intense. Three localities yielded ages between 7.3 and 7.0 Ma which, along with 2 previous 7 Ma ages, firmly establishes that back-arc activity began as early as late Miocene. Volcanism continued through the Pleistocene but the peak was in the early Pliocene. This result has important tectonic implications. If, as previously suggested, magma genesis is related to lithospheric delamination, this process was underway by the latest Miocene in the southern Puna. Furthermore, since the mafic back-arc volcanism is considered to mark a change in fault kinematics from compressional to transtensional, the new age constraints indicate that this change took place in the early Pliocene. The spatial and age distributions of the mafic centers indicate that magmatism began, and remained focussed in, a region between Salar de Antofalla and Cerro Galán. This concentration is probably structurally controlled, as it corresponds to the intersection of the NW–SE striking Archibarca lineament zone and the sets of NNE–SSW faults that run parallel to the Salar de Antofalla basin.
    Type: Article , PeerReviewed
    Format: text
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  • 5
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    Unknown
    Mineralogical Society of America
    Publication Date: 2011-10-01
    Description: Tourmaline occurs in diverse types of hydrothermal mineral deposits and can be used to constrain the nature and evolution of ore-forming fluids. Because of its broad range in composition and retention of chemical and isotopic signatures, tourmaline may be the only robust recorder of original mineralizing processes in some deposits. Microtextures and in situ analysis of compositional and isotopic variations in ore-related tourmaline provide valuable insights into hydrothermal systems in seafloor, sedimentary, magmatic, and metamorphic environments. Deciphering the hydrothermal record in tourmaline also holds promise for aiding exploration programs in the search for new ore deposits.
    Print ISSN: 1811-5209
    Electronic ISSN: 1811-5217
    Topics: Geosciences
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  • 6
    Publication Date: 2023-01-30
    Description: Here we present zircon petrochronological data, tephra whole-rock/glass compositions, and amphibole thermobarometry comprising the last four explosive eruptions of Ilopango Caldera in El Salvador (Tierra Blanca eruptive suite, TB). Our datasets include 238U-230Th disequilibrium geochronology, trace-elements, and oxygen isotope compositions from polished and unpolished zircon crystals analyzed using a CAMECA IMS 1280-HR secondary ion mass spectrometer (SIMS) at Heidelberg University, Germany. Additionally, pumice clasts whole-rock chemical analyses from the TB suite were performed at the German Research Centre for Geosciences (GFZ) using a PANalytical AXIOS Advanced wavelength-dispersive spectrometer, whereas major and trace-elements, glass shard, and mineral compositions were collected using an electron microprobe analysis (EMPA) at GEOMAR - Helmholtz-Centre for Ocean Research Kiel and by Laser Ablation Inductively Coupled Plasma - Mass Spectrometry (LA-ICP-MS) at Institute of Earth Sciences, Academia Sinica in Taipei. Whole-rock Sr-Nd isotope determinations were carried out at Departamento de Geología, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE; Mexico) with a Nu-Instruments thermal ionization mass spectrometer (Nu-TIMS), whereas whole-rock U-series were determined using a ThermoFisher Neptune inductively-coupled mass-spectrometer multi-collector (ICP-MS-MC) at the University of Wyoming (UWYO, USA).
    Keywords: Central America; E009; E012; E014; E015; E017; E021; E023; E044; E047; E053; Geochemistry; geochronology; GLASS; ROCK; Rock sample; TB_E020; TB_E021; TB_E022; TB_E029; TB_E032; TB_E033; TB_E035; TB_E038; TB_E039; TB_E040; TB_E042; TB_E043; TB_E044; TB_E078; TB_E079; TB_E084; zircon
    Type: Dataset
    Format: application/zip, 8 datasets
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  • 7
    Publication Date: 2023-01-30
    Description: This dataset includes results from oxygen isotope compositions from zircon crystal interiors (polished sections) of the Tierra Blanca Joven (TBJ) eruption from Ilopango caldera in El Salvador. Zircon crystals were analyzed employing Secondary Ion Mass Spectrometry at Heidelberg University.
    Keywords: Central America; Comment; Domain, mineralogy; Geochemistry; geochronology; GLASS; ROCK; Rock sample; Sample code/label; TB_E17-32; zircon; δ18O; δ18O, standard deviation
    Type: Dataset
    Format: text/tab-separated-values, 264 data points
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  • 8
    Publication Date: 2023-01-30
    Description: This dataset includes results from U-Pb dating from zircon crystal interiors (polished sections) of the Tierra Blanca Joven eruption (TBJ) from Ilopango caldera in El Salvador. Zircon crystals were analyzed employing Secondary Ion Mass Spectrometry at Heidelberg University.
    Keywords: Age, dated; Age, dated standard error; Central America; Comment; Correlation; Domain, mineralogy; Geochemistry; geochronology; GLASS; Lead-204/Lead-206, standard error; Lead-204/Lead-206 ratio; Lead-207/Lead-206, standard error; Lead-207/Lead-206 ratio; Lead-208/Lead-206 ratio; Lead-208/Lead-206 ratio, standard error; ROCK; Rock sample; Sample code/label; TB_E17-32; Thorium/Uranium ratio; Uranium; Uranium-238/Lead-206, standard error; Uranium-238/Lead-206 ratio; zircon
    Type: Dataset
    Format: text/tab-separated-values, 473 data points
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  • 9
    Publication Date: 2023-02-12
    Description: This dataset includes results from U-Th disequilibria dating from zircon rims (outermost crystal face) and crystal interiors (polished crystals) of the last four explosive silicic eruptions from Ilopango caldera in El Salvador (TBJ, TB2, TB3, and TB4). Zircon crystals were analyzed employing Secondary Ion Mass Spectrometry at Heidelberg University.
    Keywords: Age, dated; Age, dated, error to older; Age, dated, error to younger; Central America; Comment; Domain, mineralogy; Event label; Geochemistry; geochronology; GLASS; ROCK; Rock sample; Sample code/label; Sample type; TB_E17-1; TB_E17-17; TB_E17-32; TB_E17-4; Thorium-230/Thorium-232 activity ratio; Thorium-230/Thorium-232 activity ratio, standard error; Uranium; Uranium-238/Thorium-232 activity ratio; Uranium-238/Thorium-232 activity ratio, standard error; zircon; Zircon-melt model isochron slope; Zircon-melt model isochron slope, standard error
    Type: Dataset
    Format: text/tab-separated-values, 3144 data points
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  • 10
    Publication Date: 2023-02-12
    Description: This dataset includes results from trace element concentrations from zircon rims (outermost crystal face) and crystal interiors (polished sections) of the last four explosive silicic eruptions from Ilopango caldera (TBJ, TB2, TB3, and TB4) in El Salvador. Zircon crystals were analyzed employing Secondary Ion Mass Spectrometry at Heidelberg University.
    Keywords: Age, dated; Age, dated, error to older; Age, dated, error to younger; Age, dated standard error; Central America; Cerium; Cerium, standard error; Comment; Domain, mineralogy; Dysprosium; Dysprosium, standard error; Erbium; Erbium, standard error; Europium; Europium, standard error; Europium anomaly; Europium anomaly, standard error; Event label; Gadolinium; Gadolinium, standard error; Geochemistry; geochronology; GLASS; Hafnium; Hafnium, standard error; Holmium; Holmium, standard error; Iron; Iron, standard error; Lanthanum; Lanthanum, standard error; Light rare-earth elements index; Lutetium; Lutetium, standard error; Magnesium; Magnesium, standard error; Manganese; Manganese, standard error; Neodymium; Neodymium, standard error; Phosphorus; Phosphorus, standard error; Praseodymium; Praseodymium, standard error; ROCK; Rock sample; Samarium; Samarium, standard error; Sample code/label; Sample type; TB_E17-1; TB_E17-17; TB_E17-32; TB_E17-4; Terbium; Terbium, standard error; Thorium; Thorium, standard error; Thorium/Uranium, standard error; Thorium/Uranium ratio; Thulium; Thulium, standard error; Ti-in-zircon temperature, calculated; Ti-in-zircon temperature, calculated, error; Titanium; Titanium, standard error; Uranium; Uranium, standard error; Ytterbium; Ytterbium, standard error; Ytterbium/Dysprosium, standard error; Ytterbium/Dysprosium ratio; Yttrium; Yttrium, standard error; zircon; Zirconium/Hafnium, standard error; Zirconium/Hafnium ratio; δ18O; δ18O, standard deviation
    Type: Dataset
    Format: text/tab-separated-values, 11956 data points
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