Preprints

Filtering by Subject: Geochemistry

Comparative study of alteration sequences in pegmatitic aluminium phosphates

Cassian P. F. Pirard

Published: 2022-09-29
Subjects: Earth Sciences, Geochemistry, Geology, Mineral Physics, Other Earth Sciences

Aluminium phosphates are mineral phases commonly occurring in rare-element pegmatites that record initial magmatic crystallization, metasomatic and hydrothermal replacements and precipitation and low-temperature alteration. Here we perform a comparative mineralogical study between several localities to assess similarities and variations in these parageneses and establish a general alteration [...]

All aboard! Earth system investigations with the CH2O-CHOO TRAIN v1.0

Tyler Kukla, Daniel Enrique Ibarra, Kimberly V. Lau, et al.

Published: 2022-09-24
Subjects: Climate, Earth Sciences, Geochemistry, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics

Models of the carbon cycle and climate on geologic (>10^4 year) timescales have improved tremendously in the last 50 years due to parallel advances in our understanding of the Earth system and the increase in computing power to simulate its key processes. Despite these advances, balancing the Earth System's vast complexity with a model's computational expense is a primary challenge in model [...]

Characterisation of phosphate mineralogy in Montebras-en-Soumans Pegmatite, Massif Central, France

Cassian P. F. Pirard

Published: 2022-09-22
Subjects: Earth Sciences, Geochemistry, Geology, Mineral Physics

Montebras-en-Soumans pegmatitic cupola hosts large pods of phosphate composed of primary amblygonite-montebrasite. These aluminium phosphate masses are considerably altered by post-magmatic processes producing a number of secondary metasomatic hydrothermal phosphates (lacroixite, wardite, morinite, viitaniemiite, apatite, triplite, eosphorite) and low-temperature phosphates (apatite, crandallite, [...]

python-ags4: A Python library to read, write, and validate AGS4 geodata files

Asitha Senanayake, Roger Chandler, Tony Daly, et al.

Published: 2022-09-21
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Environmental Engineering, Geochemistry, Geology, Geophysics and Seismology, Geotechnical Engineering

Data gathered from geotechnical, geoenvironmental, and geophysical investigations can be broadly described as "geodata". The AGS4 data format is one of the most widely used data transmittal formats for geodata and is used across the world. It is a plain text format consisting of multiple tables of comma-separated values, tied together with a robust data schema and a comprehensive suite of [...]

North Atlantic Drift Sediments Constrain Eocene Tidal Dissipation and the Evolution of the Earth-Moon System

David De Vleeschouwer, Donald Penman, Simon D'haenens, et al.

Published: 2022-09-15
Subjects: Geochemistry, Geology, Sedimentology, Stratigraphy

Cyclostratigraphy and astrochronology are now at the forefront of geologic timekeeping. While this technique heavily relies on the accuracy of astronomical calculations, solar system chaos limits how far back astronomical calculations can be performed with confidence. High-resolution paleoclimate records with Milankovitch imprints now allow reversing the traditional cyclostratigraphic approach: [...]

A genetic model of the magnetite-apatite deposits on El Laco volcano by extrusion of iron-rich melt

Tobias Keller, Fernando Tornos, John M. Hanchar, et al.

Published: 2022-08-25
Subjects: Dynamical Systems, Earth Sciences, Fluid Dynamics, Geochemistry, Geology, Numerical Analysis and Scientific Computing, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology

Magnetite-apatite deposits are important sources of iron and other metals. A prominent exam- ple are the magnetite lavas at the El Laco volcano, Northern Chile. Their formation processes remain debated. Here, we test the genetic hypothesis that an Fe-rich melt separated from silicate magma and ascended along collapse-related fractures. We complement recent analy- ses with thermodynamic modelling [...]

Sampling across large-scale geological gradients to study geosphere-biosphere interactions

Donato Giovannelli, Peter H. Barry, Joost M de Moor, et al.

Published: 2022-07-25
Subjects: Biogeochemistry, Earth Sciences, Environmental Sciences, Geochemistry, Life Sciences, Microbiology

Despite being one of the largest microbial ecosystems on Earth, with >1029 microbial cells, many basic open questions remain about how life exists and thrives in the deep subsurface biosphere, inside Earth’s crust. Much of this ambiguity is due to the fact that it is exceedingly difficult and (often prohibitively expensive) to directly sample the deep subsurface, requiring elaborate drilling [...]

Evaluation of preservation protocols for oxygen-sensitive minerals within laminated aquatic sediments

Gabrielle Ledesma, Raisa Islam, Elizabeth Swanner Smith

Published: 2022-07-25
Subjects: Biogeochemistry, Environmental Sciences, Geochemistry, Sedimentology

Laminated sediments can record seasonal changes in sedimentation of material from anoxic waters, including minerals of the redox-sensitive elements Fe, Mn, and S that form under varying oxygen levels, mineral saturation conditions, and from microbial metabolism. However, preserving both the oxygen-sensitive minerals for identification is challenging when preservation of the spatial arrangement of [...]

Slab to back-arc to arc: fluid and melt pathways through the mantle wedge beneath the Lesser Antilles

Stephen Paul Hicks, Lidong Bie, Catherine Rychert, et al.

Published: 2022-07-14
Subjects: Earth Sciences, Geochemistry, Geophysics and Seismology, Tectonics and Structure, Volcanology

Volatiles expelled from subducted plates melt the overlying warm mantle, feeding arc volcanism. However, debates continue over the factors controlling melt generation and transport and how these determine the placement of volcanoes. To broaden our synoptic view of these fundamental mantle wedge processes, we image seismic attenuation beneath the Lesser Antilles arc, an end-member system that [...]

Barren ground depressions, natural H2 and orogenic gold deposits: spatial link and geochemical model

Benjamin Malvoisin, Fabrice Brunet

Published: 2022-07-11
Subjects: Earth Sciences, Ecology and Evolutionary Biology, Geochemistry, Geology, Geomorphology, Soil Science

A review of the localities in continental rocks where H2-rich gases have been reported, showed that they are mainly located near gold deposits. Two types of geomorphological features known as markers of gas venting in sedimentary basins were also systematically observed near orogenic gold deposits on satellite images. They consist in both barren ground depressions and high densities of small (< [...]

Evolution of diversity in the editorial boards of Geochimica et Cosmochimica Acta and Chemical Geology

Olivier Pourret, Pallavi Anand, Pieter Bots, et al.

Published: 2022-06-24
Subjects: Geochemistry, Physical Sciences and Mathematics

Background: Editorial board members of academic journals are often considered gatekeepers of knowledge and role models for the community. Editorial boards should have sufficiently diverse backgrounds to facilitate the publication of manuscripts with a wide range of research paradigms, methods, and cultural perspectives. Objectives: This study critically evaluates changes in the representation of [...]

Pervasive carbonation of peridotite to listvenite (Semail Ophiolite, Sultanate of Oman): clues from iron partitioning and chemical zoning

Thierry Decrausaz, Marguerite Godard, Manuel D. Menzel, et al.

Published: 2022-06-21
Subjects: Geochemistry, Geology

Earth’s long-term cycling of carbon is regulated from mid-ocean ridges to convergent margins by mass transfers involving mantle rocks. Here we examine the conversion of peridotite into listvenite (magnesite+quartz) occurring along the basal thrust of the Semail Ophiolite (Fanja, Sultanate of Oman). At the outcrop scale, this transformation defines reaction fronts, from serpentinized peridotites, [...]

Validation of glacial-interglacial rainfall variations in southwest Sulawesi using Mg/Ca and δ18O in speleothems

Alena K Kimbrough, Michael Gagan, Gavin Dunbar, et al.

Published: 2022-06-17
Subjects: Atmospheric Sciences, Climate, Earth Sciences, Geochemistry, Hydrology, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Speleology

Speleothem δ18O is widely used as a proxy for rainfall amount in the tropics on glacial-interglacial to interannual scales. However, uncertainties in the interpretation of this renowned proxy pose a vexing problem in tropical paleoclimatology. Here, we present paired measurements of Mg/Ca and δ18O for multiple stalagmites from southwest Sulawesi, Indonesia, that that confirm changes in rainfall [...]

The historical impact of anthropogenic air-borne sulphur on the Pleistocene rock art of Sulawesi

Michael Gagan, Halmar Halide, Raden Permana, et al.

Published: 2022-05-31
Subjects: Earth Sciences, Environmental Indicators and Impact Assessment, Environmental Sciences, Geochemistry, Natural Resources and Conservation

The Maros-Pangkep karst in southwest Sulawesi, Indonesia, contains some of the world’s oldest rock art. However, the Pleistocene images survive only as weathered patches of pigment on exfoliated limestone surfaces. Salt efflorescence underneath the case-hardened limestone substrate causes spall-flaking, and it has been proposed that the loss of artwork has accelerated over recent decades. Here, [...]

Paleoclimate controls on lithium enrichment in Great Basin Pliocene-Pleistocene lacustrine clays

Catherine A Gagnon, Kristina Butler, Elizabeth Gaviria, et al.

Published: 2022-05-29
Subjects: Climate, Earth Sciences, Environmental Sciences, Geochemistry, Geology, Natural Resources and Conservation, Other Environmental Sciences, Sedimentology

Terminal lakes are important archives of continental hydroclimate and in some cases contain important economic resources. Here we present an ~3.6 Myr lacustrine carbonate carbon and oxygen stable isotope record from a Great Basin continental drill core. We pair these measurements with bulk lithium concentrations to reveal a relationship between past climate and lithium enrichment in authigenic [...]

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