Preprints
Filtering by Subject: Geochemistry
Effects of mineralogy on ∆47 and ∆48 of carbonate-derived CO2 below analytical resolution
Published: 2025-02-19
Subjects: Geochemistry
Due to the lack of direct methods capable of determining the abundance of isotopologues containing multiple heavy isotopes within the crystal lattice, carbonates are typically reacted with phosphoric acid to produce CO2 analyte for clumped isotope analyses. This reaction is associated with fractionations of both bulk oxygen and clumped isotopes. Accurate knowledge of the effect of cation [...]
Geochemistry and Mineralogy of Ilmenite Exsolutions in Titanomagnetite and Their Implications for the Ore-Forming Process at the Damiao Deposit
Published: 2025-02-15
Subjects: Geochemistry, Geology
The Damiao Fe-Ti-P deposit, located within the Damiao anorthosite complex in northeastern China, features Fe-Ti oxide ores and nelsonites that occur as irregularly inclined stratiform-like bodies, lenses, or veins with sharp contacts against anorthosite and gabbronorite. This deposit is characterized by abundant titanomagnetite that hosts diverse ilmenite exsolution textures, including blocky, [...]
Glacially enhanced silicate weathering revealed by Holocene lake records
Published: 2025-02-08
Subjects: Biogeochemistry, Earth Sciences, Geochemistry, Physical Sciences and Mathematics
How glaciation affects CO2 drawdown by chemical weathering sets the strength of the weathering-climate feedback, which controls the exogenic carbon cycle and planetary habitability (Kump et al., 2000). However, the exact role of glaciers remains elusive as glaciation alters multiple factors controlling weathering, the net effect of which is ambiguous even in directionality. While illustrative, [...]
Widely variable granite production from a restitic metasedimentary terrane by volatile redistribution
Published: 2025-01-24
Subjects: Earth Sciences, Geochemistry, Geology, Other Earth Sciences
The amount of melt extracted from a metasedimentary source is a major parameter in quantitative models of crustal processes; however, quantification of melt volume is thwarted by the heterogeneity of the crust and a lack of estimates concerning the amount of fluid present. We observe that highly systematic trends in metasedimentary rocks allow treatment of protoliths as two component mixtures, [...]
Algal lipid distributions and hydrogen isotope ratios reflect phytoplankton community dynamics
Published: 2025-01-21
Subjects: Earth Sciences, Geochemistry, Paleobiology, Physical Sciences and Mathematics, Sedimentology
Reconstructions of past changes in algal community composition provide important context for future alterations in biogeochemical cycling. However, many existing phytoplankton proxies are indicative of individual algal groups and are not fully representative of the whole community. Here, we evaluated hydrogen isotope ratios of algal lipids (δ2HLipid) as a potential proxy for phytoplankton [...]
Divergent Paradigms of Porphyry Cu Deposits in Subduction and Collision Zones
Published: 2025-01-09
Subjects: Geochemistry, Geology, Natural Resource Economics, Physical Sciences and Mathematics
The prevailing view suggests that the formation of porphyry Cu deposits involves differentiation of water-rich, metal-bearing juvenile magmas, with subduction of oceanic slabs supplying the necessary volatiles. However, the occurrence of significant porphyry Cu deposits in continental collision zones, where such volatile sources are absent, challenges this paradigm. We analyze a global dataset of [...]
Water Storage in Hydrous Minerals in the Shallow Martian Mantle
Published: 2025-01-06
Subjects: Earth Sciences, Geochemistry, Geology, Planetary Geochemistry
In this paper we investigate the possibility of storing water in the shallow martian mantle under water-saturated fluid absent conditions for different bulk silicate mars (BSM) compositions. We performed phase equilibria experiments on two BSM compositions with comparable Mg number for pressure between 2 and 4 GPa, temperatures between 950 to 1150°C, and for a water content of 0.3 % wt. The [...]
Cambrian foreland phosphogenesis in the Khuvsgul Basin of Mongolia
Published: 2024-12-27
Subjects: Earth Sciences, Geochemistry, Geology, Sedimentology, Stratigraphy, Tectonics and Structure
Ediacaran-Cambrian phosphorite deposits in northern Mongolia have been associated with a putative increase in nutrient delivery to the global oceans that drove oxygenation and the rise of animals. However, like many phosphorites from this ~130 Myr interval, the precise age and depositional setting of these deposits remain poorly constrained. Here, we integrate new geological mapping, [...]
Disappearance of Homo floresiensis from Liang Bua alongside seasonal aridification of Flores 61,000-47,000 years ago
Published: 2024-12-10
Subjects: Atmospheric Sciences, Climate, Environmental Indicators and Impact Assessment, Fresh Water Studies, Geochemistry, Hydrology, Paleobiology, Physical Sciences and Mathematics, Speleology
The cause of the disappearance of the primitive hominin, Homo floresiensis, from the Indonesian island of Flores ~50,000 years ago is a key question in palaeoanthropology. The potential roles of human agency and climate change continue to be debated, but the history of freshwater availability critical to survival at the type locality, Liang Bua, remains unknown. Although speleothem 18O is used [...]
A Millimeter-Scale Change in Leaf Litter Placement Within Soil-Water Interfaces Alters Carbon Dioxide and Methane Emission
Published: 2024-12-04
Subjects: Earth Sciences, Environmental Sciences, Geochemistry, Soil Science, Sustainability
Flooded soils play a critical role in global carbon cycling, serving as significant reservoirs of soil organic carbon and sources of carbon emissions. Leaf litter, particularly from local vegetation, is a major contributor to soil organic carbon formation in these ecosystems, with its decomposition driving the production of carbon dioxide and methane. While numerous studies have investigated the [...]
Ocean and Coastal Acidification Monitoring Priorities for the Northeast US and Eastern Canada
Published: 2024-11-07
Subjects: Environmental Monitoring, Geochemistry, Oceanography, Planetary Geochemistry
The Interagency Working Group on Ocean Acidification monitoring Prioritization Plan 2024 calls for Coastal Acidification Networks to identify the ocean and coastal acidification (OCA) monitoring needs most important for their regions. The Northeast Coastal Acidification Network (NECAN) organized a webinar series to study regional needs, which culminated with a workshop in November 2023. This [...]
Phanerozoic thermochronology record of Afro-Arabia through space and time
Published: 2024-10-17
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics
Low-temperature thermochronology has been widely used in eastern Africa and Arabia (Afro-Arabia) to investigate the long-term thermal evolution of the crust in response to Phanerozoic tectonism. Yet, utilisation of this invaluable thermochronology record to inform numerical investigations into the long-term tectonothermal, geodynamic and landscape evolution of the region has been limited by the [...]
The link between water and ferric iron in Earth's lower mantle
Published: 2024-10-10
Subjects: Earth Sciences, Geochemistry, Mineral Physics
As the most massive geochemical reservoir, the lower mantle affects Earth's budget of volatile elements, including hydrogen or H2O. The properties of minerals in Earth's lower mantle are further affected by changes in the electronic configurations of iron cations, i.e., spin transitions. Potential feedback between deep H2O retention and spin transitions in mantle minerals, however, remain [...]
Questioning Dark Oxygen Production in the Deep-sea Ferromanganese Nodule Field
Published: 2024-10-04
Subjects: Earth Sciences, Geochemistry, Geology, Oceanography
Previous studies have concluded that the natural process where oxygen is consumed as decomposition of organic matter that supplied from shallow waters occurs on the deep-sea floor. Sweetman et al.1 presented the surprising observation that deep-sea ferromanganese nodules generate oxygen, which they labelled as dark oxygen production. The authors claimed that oxygen was generated through the [...]
Hadean-aged felsic sediments recycled through the deep mantle by early plate tectonics
Published: 2024-10-02
Subjects: Geochemistry, Geology
The question of when modern tectonic processes arose on Earth has restricted our understanding of how and how quickly Earth reached its present, habitable form. Plate tectonics, and in particular deep subduction, is central to many facets of habitability: it controls heat flow, biogeochemical cycling, and creates a variety of marine and terrestrial biomes necessary for biological evolution. Many [...]