Subjects -> EARTH SCIENCES (Total: 771 journals)
    - EARTH SCIENCES (527 journals)
    - GEOLOGY (94 journals)
    - GEOPHYSICS (33 journals)
    - HYDROLOGY (29 journals)
    - OCEANOGRAPHY (88 journals)

EARTH SCIENCES (527 journals)                  1 2 3 | Last

Showing 1 - 200 of 371 Journals sorted by number of followers
Nature Geoscience     Full-text available via subscription   (Followers: 161)
IEEE Geoscience and Remote Sensing Letters     Hybrid Journal   (Followers: 149)
International Journal of Remote Sensing     Hybrid Journal   (Followers: 144)
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 141)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 133)
Journal of the Atmospheric Sciences     Hybrid Journal   (Followers: 83)
Ocean & Coastal Management     Hybrid Journal   (Followers: 62)
Marine Policy     Hybrid Journal   (Followers: 60)
International Journal of Geographical Information Science     Hybrid Journal   (Followers: 55)
Geochimica et Cosmochimica Acta     Hybrid Journal   (Followers: 54)
ICES Journal of Marine Science: Journal du Conseil     Hybrid Journal   (Followers: 53)
Natural Hazards     Hybrid Journal   (Followers: 53)
Journal of Earth System Science     Open Access   (Followers: 52)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 44)
Hydrological Processes     Hybrid Journal   (Followers: 44)
Estuarine, Coastal and Shelf Science     Hybrid Journal   (Followers: 41)
Journal of Hydrologic Engineering     Full-text available via subscription   (Followers: 40)
Geophysical Journal International     Hybrid Journal   (Followers: 39)
Groundwater     Hybrid Journal   (Followers: 37)
International Journal of Earth Sciences     Hybrid Journal   (Followers: 37)
International Journal of Applied Earth Observation and Geoinformation     Open Access   (Followers: 36)
Physics of the Earth and Planetary Interiors     Hybrid Journal   (Followers: 34)
Journal of Atmospheric and Oceanic Technology     Hybrid Journal   (Followers: 33)
Geomorphology     Hybrid Journal   (Followers: 33)
Chemical Geology     Hybrid Journal   (Followers: 31)
Marine Geology     Hybrid Journal   (Followers: 31)
Geology Today     Hybrid Journal   (Followers: 31)
Marine Environmental Research     Hybrid Journal   (Followers: 31)
Journal of Quaternary Science     Hybrid Journal   (Followers: 31)
Reviews of Modern Physics     Full-text available via subscription   (Followers: 30)
Journal of Geotechnical and Geoenvironmental Engineering     Full-text available via subscription   (Followers: 30)
Journal of Geology     Full-text available via subscription   (Followers: 30)
Coastal Management     Hybrid Journal   (Followers: 29)
Advances In Physics     Hybrid Journal   (Followers: 29)
GPS Solutions     Hybrid Journal   (Followers: 28)
Bulletin of the Seismological Society of America     Full-text available via subscription   (Followers: 26)
Landslides     Hybrid Journal   (Followers: 26)
Journal of Structural Geology     Hybrid Journal   (Followers: 26)
Quaternary Science Reviews     Hybrid Journal   (Followers: 26)
Ground Water Monitoring & Remediation     Hybrid Journal   (Followers: 25)
Geoforum     Hybrid Journal   (Followers: 25)
Earth Surface Processes and Landforms     Hybrid Journal   (Followers: 25)
Environmental Geology     Hybrid Journal   (Followers: 25)
Tectonophysics     Hybrid Journal   (Followers: 24)
Geocarto International     Hybrid Journal   (Followers: 23)
Coral Reefs     Hybrid Journal   (Followers: 22)
Bulletin of Volcanology     Hybrid Journal   (Followers: 22)
Hydrogeology Journal     Hybrid Journal   (Followers: 21)
Hydrobiologia     Hybrid Journal   (Followers: 21)
Tellus A     Open Access   (Followers: 21)
Marine and Petroleum Geology     Hybrid Journal   (Followers: 21)
Water Resources     Hybrid Journal   (Followers: 21)
Journal of Plasma Physics     Hybrid Journal   (Followers: 21)
Earthquake Spectra     Hybrid Journal   (Followers: 20)
Tellus B     Open Access   (Followers: 20)
Journal of Marine Research     Full-text available via subscription   (Followers: 20)
Sedimentary Geology     Hybrid Journal   (Followers: 20)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 19)
Geophysics     Full-text available via subscription   (Followers: 19)
Quaternary Research     Full-text available via subscription   (Followers: 19)
Geological Journal     Hybrid Journal   (Followers: 19)
Global and Planetary Change     Hybrid Journal   (Followers: 18)
Physics of Metals and Metallography     Hybrid Journal   (Followers: 18)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 17)
Computational Geosciences     Hybrid Journal   (Followers: 17)
Journal of Volcanology and Geothermal Research     Hybrid Journal   (Followers: 17)
Natural Hazards Review     Full-text available via subscription   (Followers: 16)
Geological Magazine     Hybrid Journal   (Followers: 16)
The Holocene     Hybrid Journal   (Followers: 16)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 16)
Journal of Metamorphic Geology     Hybrid Journal   (Followers: 15)
Journal of Applied Geophysics     Hybrid Journal   (Followers: 15)
Journal of Asian Earth Sciences     Hybrid Journal   (Followers: 15)
Sedimentology     Hybrid Journal   (Followers: 15)
Ocean Development & International Law     Hybrid Journal   (Followers: 15)
Applied Geochemistry     Hybrid Journal   (Followers: 14)
Quaternary International     Hybrid Journal   (Followers: 14)
Journal of the World Aquaculture Society     Hybrid Journal   (Followers: 13)
Journal of Hydro-environment Research     Full-text available via subscription   (Followers: 13)
Pramana     Open Access   (Followers: 13)
Soil Dynamics and Earthquake Engineering     Hybrid Journal   (Followers: 13)
Electromagnetics     Hybrid Journal   (Followers: 13)
Ocean Modelling     Hybrid Journal   (Followers: 12)
European Journal of Mineralogy     Hybrid Journal   (Followers: 12)
Frontiers of Earth Science     Hybrid Journal   (Followers: 12)
Continental Shelf Research     Hybrid Journal   (Followers: 12)
Computers and Geotechnics     Hybrid Journal   (Followers: 12)
Arctic, Antarctic, and Alpine Research     Open Access   (Followers: 12)
Pure and Applied Geophysics     Hybrid Journal   (Followers: 12)
CATENA     Hybrid Journal   (Followers: 11)
Journal of Petrology     Hybrid Journal   (Followers: 11)
Ore Geology Reviews     Hybrid Journal   (Followers: 11)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 11)
Applied Geophysics     Hybrid Journal   (Followers: 11)
Journal of African Earth Sciences     Hybrid Journal   (Followers: 11)
IEEE Journal of Oceanic Engineering     Hybrid Journal   (Followers: 11)
Marine Mammal Science     Hybrid Journal   (Followers: 10)
Cretaceous Research     Hybrid Journal   (Followers: 10)
Earth Interactions     Open Access   (Followers: 10)
Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia     Hybrid Journal   (Followers: 10)
Bulletin of Earthquake Engineering     Hybrid Journal   (Followers: 10)
Gondwana Research     Hybrid Journal   (Followers: 10)
Physics of Plasmas     Hybrid Journal   (Followers: 10)
Journal of Seismology     Hybrid Journal   (Followers: 9)
Physik in unserer Zeit     Hybrid Journal   (Followers: 9)
Lithos     Hybrid Journal   (Followers: 9)
Limnology     Hybrid Journal   (Followers: 9)
Acta Geophysica     Hybrid Journal   (Followers: 9)
Journal of Contemporary Physics (Armenian Academy of Sciences)     Hybrid Journal   (Followers: 9)
Journal of Marine Systems     Hybrid Journal   (Followers: 9)
Geotectonics     Hybrid Journal   (Followers: 9)
Facies     Hybrid Journal   (Followers: 9)
Comptes Rendus : Geoscience     Open Access   (Followers: 9)
Journal of Geodesy     Hybrid Journal   (Followers: 9)
Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards     Hybrid Journal   (Followers: 8)
Geophysical & Astrophysical Fluid Dynamics     Hybrid Journal   (Followers: 8)
Natural Resources Research     Hybrid Journal   (Followers: 8)
Geobiology     Hybrid Journal   (Followers: 8)
Quaternary Geochronology     Hybrid Journal   (Followers: 8)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 8)
Geophysical Prospecting     Hybrid Journal   (Followers: 7)
Journal of Systematic Palaeontology     Hybrid Journal   (Followers: 7)
Physics of the Solid State     Hybrid Journal   (Followers: 7)
Plasma Physics Reports     Hybrid Journal   (Followers: 7)
Precambrian Research     Hybrid Journal   (Followers: 7)
Ocean Engineering     Hybrid Journal   (Followers: 6)
Petrology     Full-text available via subscription   (Followers: 6)
Applied Clay Science     Hybrid Journal   (Followers: 6)
Journal of Sea Research     Hybrid Journal   (Followers: 6)
Geochemistry : Exploration, Environment, Analysis     Hybrid Journal   (Followers: 6)
Acta Geotechnica     Hybrid Journal   (Followers: 6)
Geo-Marine Letters     Hybrid Journal   (Followers: 6)
Journal of Coastal Conservation     Hybrid Journal   (Followers: 6)
Applied Ocean Research     Hybrid Journal   (Followers: 6)
Rock Mechanics and Rock Engineering     Hybrid Journal   (Followers: 6)
Chinese Geographical Science     Hybrid Journal   (Followers: 6)
Journal of Geodynamics     Hybrid Journal   (Followers: 6)
Resource Geology     Hybrid Journal   (Followers: 6)
Marine and Freshwater Research     Hybrid Journal   (Followers: 6)
Ocean Dynamics     Hybrid Journal   (Followers: 6)
International Journal of Geomechanics     Full-text available via subscription   (Followers: 6)
Island Arc     Hybrid Journal   (Followers: 5)
Geofluids     Open Access   (Followers: 5)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 5)
Marine Geophysical Researches     Hybrid Journal   (Followers: 5)
Geochemistry     Hybrid Journal   (Followers: 5)
Permafrost and Periglacial Processes     Hybrid Journal   (Followers: 5)
Zeitschrift für Geomorphologie     Full-text available via subscription   (Followers: 5)
Terra Nova     Hybrid Journal   (Followers: 5)
Energy Exploration & Exploitation     Open Access   (Followers: 4)
Organic Geochemistry     Hybrid Journal   (Followers: 4)
Mineralium Deposita     Hybrid Journal   (Followers: 4)
Marine Geodesy     Hybrid Journal   (Followers: 4)
Limnologica     Hybrid Journal   (Followers: 4)
Meteorologische Zeitschrift     Full-text available via subscription   (Followers: 4)
Letters in Mathematical Physics     Hybrid Journal   (Followers: 4)
Geostandards and Geoanalytical Research     Hybrid Journal   (Followers: 3)
Surveys in Geophysics     Hybrid Journal   (Followers: 3)
Lithology and Mineral Resources     Hybrid Journal   (Followers: 3)
Russian Geology and Geophysics     Hybrid Journal   (Followers: 3)
Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 3)
JETP Letters     Hybrid Journal   (Followers: 3)
Mathematical Physics, Analysis and Geometry     Hybrid Journal   (Followers: 3)
Fundamental and Applied Limnology / Archiv für Hydrobiologie     Full-text available via subscription   (Followers: 3)
Contributions to Plasma Physics     Hybrid Journal   (Followers: 3)
Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen     Full-text available via subscription   (Followers: 3)
Geomagnetism and Aeronomy     Hybrid Journal   (Followers: 3)
Journal of Petroleum Science and Engineering     Hybrid Journal   (Followers: 3)
Journal of Marine Science and Technology     Hybrid Journal   (Followers: 3)
Zeitschrift der Deutschen Gesellschaft für Geowissenschaften     Full-text available via subscription   (Followers: 3)
Stratigraphy and Geological Correlation     Full-text available via subscription   (Followers: 2)
Annales Henri Poincaré     Hybrid Journal   (Followers: 2)
Rocks & Minerals     Hybrid Journal   (Followers: 2)
Newsletters on Stratigraphy     Full-text available via subscription   (Followers: 2)
Polar Record     Hybrid Journal   (Followers: 2)
Mineralogy and Petrology     Hybrid Journal   (Followers: 2)
International Journal of Coal Geology     Hybrid Journal   (Followers: 2)
Helgoland Marine Research     Open Access   (Followers: 2)
Journal of Geophysics and Engineering     Hybrid Journal   (Followers: 2)
Izvestiya, Physics of the Solid Earth     Hybrid Journal   (Followers: 2)
Journal of Mining Science     Hybrid Journal   (Followers: 2)
Studia Geophysica et Geodaetica     Hybrid Journal   (Followers: 1)
The Leading Edge     Hybrid Journal   (Followers: 1)
Izvestiya, Atmospheric and Oceanic Physics     Full-text available via subscription   (Followers: 1)
Doklady Physics     Hybrid Journal   (Followers: 1)
Russian Physics Journal     Hybrid Journal   (Followers: 1)
Reports on Mathematical Physics     Full-text available via subscription   (Followers: 1)
Glass Physics and Chemistry     Hybrid Journal   (Followers: 1)
Physics of Life Reviews     Hybrid Journal   (Followers: 1)
Neues Jahrbuch für Mineralogie - Abhandlungen     Full-text available via subscription   (Followers: 1)
Russian Journal of Pacific Geology     Hybrid Journal  
Russian Journal of Mathematical Physics     Full-text available via subscription  
Physics of Wave Phenomena     Hybrid Journal  
Moscow University Physics Bulletin     Hybrid Journal  
Moscow University Geology Bulletin     Hybrid Journal  
Marine Georesources & Geotechnology     Hybrid Journal  
Journal of Mountain Science     Hybrid Journal  
Grassland Science     Hybrid Journal  
Erwerbs-Obstbau     Hybrid Journal  
Bulletin of the Lebedev Physics Institute     Hybrid Journal  

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Journal Cover
Journal of Petrology
Journal Prestige (SJR): 3.159
Citation Impact (citeScore): 4
Number of Followers: 11  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0022-3530 - ISSN (Online) 1460-2415
Published by Oxford University Press Homepage  [419 journals]
  • An Experimental Study of Chlorite Stability in Varied Subduction Zone
           Lithologies with Implications for Fluid Production, Melting, and Diapirism
           in Chlorite-Rich Mélange Rocks

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      Authors: Lakey S; Hermann J.
      Abstract: AbstractFour ultramafic bulk compositions comprising only natural minerals were used to constrain the stability field of chlorite in a variety of subducted, chlorite-rich rocks through an examination of key chlorite dehydration reactions relevant to the sub-arc. Seventy-four piston cylinder experiments were conducted at a range of pressures (1.0–5.0 GPa) and temperatures (500°C–1150°C).Bulk 1 represents a chlorite mélange (Mg# = 0.94) typically formed in the subduction channel. This composition was used to examine the terminal chlorite reactions to olivine, orthopyroxene, and spinel at low pressure and to olivine, garnet, and spinel at high pressure. Chlorite achieves a thermal maximum stability at 2.0 GPa, 850°C; at 3.0 GPa, 850°C; and at 5.0 GPa, 760°C. The terminal chlorite breakdown reaction rises at a much steeper Clapeyron slope than shown in previous studies. Bulk 2 contains additionally antigorite and tremolite, to constrain phase relations in more fertile compositions. Chlorite reacts with clinopyroxene at ~100°C lower temperatures and with orthopyroxene at ~20°C–60°C lower temperatures than the terminal chlorite breakdown. The reactions have a subparallel Clapeyron slope and none of the three chlorite dehydration reactions crosses the antigorite breakdown reaction up to 5 GPa. This demonstrates that chlorite is the most stable carrier of H2O to high temperatures in subducted ultramafic rocks. Chlorite mélanges that form at the subduction plate interface will dehydrate at 850°C–800°C, 80–120 km depth for intermediate to hot subduction geotherms and liberate 10–12 wt.% of H2O, triggering wet melting in associated sediments. For cold subduction geotherms, chlorite dehydration occurs at 780°C–740°C, 120–170 km depth. Interaction of such fluids with sediments will likely produce a supercritical fluid phase. No melting in the ultramafic rocks has been observed at the chlorite breakdown reactions. Wet melting of the chlorite mélange at 3 GPa occurred between 1100°C and 1150°C.The stability of chlorite in more Fe-rich mélanges (bulk Mg# = 0.50 and 0.68, respectively) were conducted at 3.0 GPa and revealed thermal maxima at 650°C and 765°C, respectively. Collectively, the thermal stability of chlorite is dependent upon the Mg# of the bulk composition and spans over 200°C at sub-arc depths. The density of run products was calculated to test the validity of the chlorite mélange diapir model. With the progressive breakdown of chlorite, ultramafic chlorite mélanges transform into garnet peridotite, thereby losing any buoyancy they initially possessed. This makes the likelihood of mélange diapirs as a major transport mechanism through the sub-arc unfeasible.
      PubDate: Sun, 24 Apr 2022 00:00:00 GMT
      DOI: 10.1093/petrology/egac029
      Issue No: Vol. 63, No. 4 (2022)
       
  • Controls on the Emplacement Style of Coherent Kimberlites in the Lac de
           Gras Field, Canada

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      Authors: Tovey M; Giuliani A, Phillips D, et al.
      Abstract: AbstractIn the Lac de Gras (LDG) kimberlite field, Northwest Territories, Canada, coherent kimberlites (CKs) occur as tabular dykes, pipe-shaped diatremes, and irregular bodies without well-defined geometries. Combining the morphology of CK bodies with the occurrence of fragmented olivine microcrysts allows distinction of four CK types at LDG: (1) dykes with no broken olivine; (2) CK without well-defined but probable sheet geometry and no broken olivine; (3) pipe-filling CK (pfCK) with abundant broken olivine and (4) pfCK with no broken olivine. These features suggest an intrusive origin for type 1 and, probably, type 2 CK; a high-energy extrusive emplacement for CK type 3 and a low-energy intrusive or extrusive emplacement for the CK type 4. Here, we compare petrographic and whole-rock, olivine and spinel compositional data for high-energy extrusive pfCK, low-energy pfCK and intrusive CK units to understand the factors controlling their variable emplacement styles. Extrusive CK contain more abundant groundmass phlogopite and monticellite, lower carbonate/silicate mineral abundance ratios and significantly lower dolomite and pleonaste-spinel abundances compared to intrusive CK. This indicates greater CO2 loss and higher H2O/CO2 in the melt phase for the extrusive CK during emplacement. Lower incompatible element concentrations in the extrusive CKs and different chromite Ti# and olivine rim Mg# indicate derivation from distinct primitive melt compositions. The extrusive CK feature higher ɛNdi and marginally higher ɛHfi compositions than the intrusive CK, pointing to derivation from distinct sources. These findings strongly imply that distinct primary melt compositions were largely responsible for the differences in emplacement styles of CK at LDG. Low-energy pfCKs have similar olivine rim Mg#, chromite Ti# and, hence, primitive melt compositions to the high-energy extrusive CK samples. Their marginally different emplacement styles may depend on local factors, such as changing stress regimes, or slightly different volatile concentrations. Both types of pfCK might reflect the waning stages of volcanic sequences resulting from the eruption of a segregated magma column that started with pipe excavation and the explosive emplacement of gas-rich magma (volcaniclastic kimberlite), followed by the less energetic emplacement of melt-rich magma (pfCK). This hypothesis underscores different primary melt compositions for dyke vs pipe-forming (and filling) kimberlites and hence a fundamental primary melt control on the explosivity of kimberlites.
      PubDate: Fri, 22 Apr 2022 00:00:00 GMT
      DOI: 10.1093/petrology/egac028
      Issue No: Vol. 63, No. 4 (2022)
       
  • Correction to: Zircon Trace Element and O-Hf Isotope Analyses of
           Mineralized Intrusions from El Teniente Ore Deposit, Chilean Andes:
           Constraints on the Source and Magmatic Evolution of Porphyry Cu-Mo Related
           Magmas

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      Authors: Muñoz M; Charrier R, Fanning C, et al.
      Abstract: In the original article, the words “mantle source” appear in two places by mistake:
      PubDate: Mon, 04 Apr 2022 00:00:00 GMT
      DOI: 10.1093/petrology/egac030
      Issue No: Vol. 63, No. 4 (2022)
       
  • Compositional Evolution of Interstitial Liquid After Onset of Abundant
           Fe–Ti Oxide Crystallization in Crystal Mush: Insights from Late-Stage
           Microstructures and Mineral Compositions of the Bijigou Layered Intrusion,
           Central China

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      Authors: Wang M; Wang C, Tan W.
      Abstract: ABSTRACTCompaction is important to the expulsion and compositional modification of interstitial liquid of crystal mush in the solidification of layered intrusions hosting Fe–Ti oxide mineralization. However, the compaction manner and compositional evolution of interstitial liquid after the onset of abundant Fe–Ti oxide crystallization in crystal mush are still enigmatic. In this study, we collected samples from a drill core profile across the major Fe–Ti oxide-rich segment of the Bijigou intrusion, a large and differentiated layered intrusion in Central China, and carried out a detailed study on the late-stage magmatic microstructures of rocks and crystal size distributions (CSDs) and spatial distribution patterns (SDPs) of clinopyroxene and plagioclase to examine the compaction manner of interstitial liquid. The Fe–Ti oxide-rich segment is composed of, from the base upward, a Fe–Ti oxide ore layer (~80 m), a troctolite unit (~105 m), an oxide gabbro unit (~153 m) and an apatite–oxide–gabbronorite unit (~165 m). The CSD curves for both plagioclase and clinopyroxene grains of the samples from the Fe–Ti oxide ore layer display gentle slopes for small crystals and consistent slopes for large crystals. In addition, there is a positive correlation of the SDP R-value (ratio of observed and predicted nearest neighbor distance of plagioclase/clinopyroxene) and mineral mode except plagioclase/clinopyroxene of the samples. The interstitial liquid was likely expelled by intensive pressure solution concomitant with crystallization of abundant Fe–Ti oxides, evidenced by the positive correlation of aspect ratio and alignment factor of plagioclase and the low fraction of trapped liquid (FTL) of 4–6% for the Fe–Ti oxide ore layer. The cumulus plagioclase of the Fe–Ti oxide ore layer was partially dissolved during pressure-solution compaction, leading to ambient Fe-rich interstitial liquid becoming Al-enriched in local places so that abundant amphibole and hercynite are present in the replacive symplectites adjacent to cumulus plagioclase. Above the Fe–Ti oxide ore layer, plagioclase grains in the samples from the troctolite unit show consistent slopes of the CSD curves and negative correlation of SDP R-value and mineral mode in the SDP plot, indicating that the interstitial liquid was mainly expelled by mechanical compaction, with FTL ranging from 7 to 9%. The CSD curves for clinopyroxene grains of the samples from the oxide gabbro unit have been modified by Ostwald ripening, but the expulsion of interstitial liquid in this unit is also attributed to mechanical compaction due to higher compaction rate than accumulation rate. This study demonstrates that the compaction manner of interstitial liquid can change from pressure solution to mechanical compaction with dramatically diminishing crystallization of Fe–Ti oxides. The pressure-solution compaction accompanying with large amounts of Fe–Ti oxides can remarkably modify the composition of interstitial liquid. This study also demonstrates that a combined measurement of CSDs and SDPs for cumulus minerals can be used to quantify the compaction manner of interstitial liquid during solidification of layered intrusions.
      PubDate: Fri, 18 Mar 2022 00:00:00 GMT
      DOI: 10.1093/petrology/egac025
      Issue No: Vol. 63, No. 4 (2022)
       
  • Platinum-Group Element Geochemistry and Magma Evolution of the Mount Hagen
           (Papua New Guinea) Magmatic System

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      Authors: Misztela M; Campbell I, Arculus R.
      Abstract: AbstractMount Hagen is a mid-Pleistocene stratovolcano located in the Papua New Guinea Highlands. It was selected for this study because of (1) its close location to several giant Cu–Au porphyry deposits in the region; (2) its high-K calc-alkaline character (absarokite–shoshonite) and (3) its wide compositional range (2 to 12 wt % MgO). Whole-rock geochemistry, petrography and QEMSCAN observations are consistent with fractional crystallisation of the evolving magma being controlled by the phases now represented by the megacrysts in the lavas: olivine and clinopyroxene at high MgO and hornblende and plagioclase at low MgO. However, the role of plagioclase is enigmatic. Although it is an abundant megacryst phase in the low-MgO samples, plagioclase has little or no influence on fractional crystallisation, suggesting that it may be an antecryst. The appearance of plagioclase megacrysts does not slow the rate of increase in Al2O3 or Sr with decreasing sample MgO and the low-MgO samples do not have Eu anomalies. At ~5.5 wt % MgO, there are significant changes in the system that are inconsistent with simple fractional crystallisation. These changes include hornblende and plagioclase replacing olivine and clinopyroxene as the principal megacryst phases, a sharp rise in platinum-group elements (PGE) concentrations, the brief reappearance of high Fo olivine megacrysts and reversed zoning in the plagioclase megacrysts. These changes are interpreted to have resulted from a new pulse of magma entering the system, with higher water, MgO, SiO2 and PGE concentrations than the original parent magma. Scatter in the PGE data is attributed to the presence of micronuggets in all samples, including the most mafic samples. We conclude that the magma system became sulphide saturated during an early stage in its fractionation history, probably before leaving the crust to deep crustal magma chamber, and then became undersaturated as a consequence of decreasing pressure as magma ascended into a mid-crustal magma chamber. The early saturation episode had a pronounced influence on PGE concentration but had little affect Cu and Au, due to their lower partition coefficient into sulphides. The magma became sulphide saturated again in the crustal magma chamber at ~8.5 wt % MgO, this time affecting all chalcophile elements. Given the early episodes of sulphide saturation, depletion in Au in the Mount Hagen magma system and the absence of a known porphyry system, it is unlikely that Mount Hagen produced economic porphyry mineralisation.
      PubDate: Mon, 14 Mar 2022 00:00:00 GMT
      DOI: 10.1093/petrology/egac023
      Issue No: Vol. 63, No. 4 (2022)
       
  • Co-Occurrence of HIMU and EM1 Components in a Single Magellan Seamount:
           Implications for the Formation of West Pacific Seamount Province

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      Authors: Wei X; Zhang Y, Shi X, et al.
      Abstract: ABSTRACTOur general understanding of mantle composition and dynamics mainly comes from the composition of lavas from oceanic intraplate volcanoes. They are generally accepted to originate from deep, relatively stationary mantle plumes. Many groups of seamounts comprising the West Pacific Seamount Province (WPSP), however, do not form long-lived, narrow and continuous chains of volcanoes with clear age progression; thus, their origin does not seem to fit this general model. Here we show a wide compositional spectrum of lavas from the Pako guyot within the Magellan seamount trail (MST), an age-progressive but short-lived volcanic chain in the WPSP. For the first time, both extreme high μ = 238U/204Pb mantle (HIMU)- and enriched mantle 1 (EM1)-like mantle plume components occur in a single seamount in the Pacific Ocean. Based on alteration resistant trace element and Sr–Nd–Pb–Hf isotopic compositions, the Pako lavas fall into three distinct groups. Group 1 has a distinctive HIMU composition with high (206Pb/204Pb)i ratios (20.41–20.94) similar to the Arago (also known as ‘Young Rurutu’ or ‘Atiu’) hotspot composition, suggesting derivation from a HIMU mantle source. Groups 2 and 3 EM1-like lavas comprise the dominant rock type and display the largest Sr–Nd–Pb–Hf isotopic variations that can be best explained by mixing between melts of focal zone (FOZO) and EM1-like mantle components. Additionally, olivine phenocrysts from Group 3 EM1-like lavas have high Ni contents, Fe/Mn and Mn/Zn ratios and low Zn/Fe*10 000 ratios, which can be explained through fractional crystallization of high-pressure partial melts from fertile peridotite. The EM1-like Groups 2 and 3 lavas are compositionally similar to the Rarotonga hotspot composition, suggesting that the MST is possibly an old trace of the Rarotonga hotspot, which is most likely a long-lived hotspot generated above a deep mantle plume. Combined with existing geochemical and tectonic data, we propose that the Magellan seamounts were likely derived from partial melting of a heterogeneous mantle plume containing HIMU, FOZO and EM1-like components. Alternatively, they could have been derived from the Arago and Rarotonga mantle plumes, each having its distinct compositional signature. The occurrence of HIMU- and EM1-like mantle plume components in a single volcano suggests that the superposition of compositionally different hotspot volcanic trails in the South Pacific could have played an important role in the generation of the WPSP.
      PubDate: Fri, 11 Mar 2022 00:00:00 GMT
      DOI: 10.1093/petrology/egac022
      Issue No: Vol. 63, No. 4 (2022)
       
  • Partitioning Behaviors of Cobalt and Manganese along Diverse Melting Paths
           of Peridotitic and MORB-Like Pyroxenitic Mantle

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      Authors: Chen C; Yao Z, Wang C.
      Abstract: AbstractThe Co, Mn, Fe, and Ni contents of olivine phenocrysts and host basalts are sensitive to source mantle lithology, which suggests they may be used to constrain the processes of mantle melting and identify basalts formed from non-peridotitic (i.e. pyroxenitic) mantle sources. Here, we use a new comprehensive, forward model involving multiple parameters to simulate partitioning of Co and Mn during partial melting of the mantle in different tectonic settings: (1) polybaric continuous melting of peridotite mantle in mid-ocean ridges can generate melts that show decreasing Co and Mn with increasing degrees of melting so that the mid-ocean ridge basalts (MORBs) contain ~39–84 μg/g Co and ~900–1600 μg/g Mn; (2) flux-melting of the mantle wedge in subduction zones tends to produce a melt that has Co increasing from ~24 to 55 μg/g and Mn from ~500 to 1110 μg/g with increasing temperature; (3) melts produced by isobaric melting of the subcontinental lithospheric mantle are also sensitive to increasing temperature and have ~35–160 μg/g Co and ~800–2600 μg/g Mn; (4) decompression melting of peridotite related to the mantle plume generates melts containing ~45–140 μg/g Co and ~1000–2000 μg/g Mn, and the abundances of these metals decrease with increasing degrees of melting; and (5) partitioning behaviors of Co, Mn, and Ni during decompression melting of MORB-like pyroxenite contrast with those during decompression melting of peridotite due to the different mineralogy and compositions in mantle lithologies, and the MORB-like pyroxenite-derived melt is metal-poor with ~25–60 μg/g Co, ~290–1600 μg/g Mn, and ~160–340 μg/g Ni. Although high-Ni, low-Mn forsteritic olivine phenocrysts and high melt Fe/Mn ratio have been proposed as diagnostic indicators of pyroxenitic components in the mantle, our models show that these features can be also generated by melting of peridotite at greater depth (i.e. a high pressure and temperature). To quantify the effect of high-pressure melting of peridotite on these diagnostic indicators, we modeled the correlations of melt Fe/Mn and olivine Co, Mn, and Ni contents with melting depth along the decompression melting path of a thermal plume. When Fe/Mn ratios of basalts and/or compositions of olivine phenocrysts deviate significantly from our modeled correlation lines, high-pressure melting of peridotite cannot explain these data, and the existence of pyroxenitic component in the mantle source is likely required. The pyroxenite-derived melt is modeled to be Ni-poor, but mixing with a peridotite-derived melt can strongly increase the partition coefficient of Ni between olivine and mixed melt, resulting in the generation of high-Ni olivine phenocrysts in plume-associated magmatic suites.
      PubDate: Tue, 08 Mar 2022 00:00:00 GMT
      DOI: 10.1093/petrology/egac021
      Issue No: Vol. 63, No. 4 (2022)
       
 
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