The University of Maine invites applications for a Ph.D. student to work in
the area of Rb-Sr geochronology by LA-ICP-MS/MS under the supervision of Dr.
https://umaine.edu/earthclimate/people/alicia-cruz-uribe/. This project
will involve in situ Rb-Sr dating of mica and other geochronology (i.e.,
U-Pb in titanite, zircon, monazite) to constrain the timing of mélange
formation. The project will likely involve some field work to collect
transects across block and rind relationships in areas where Dr. Cruz-Uribe
has worked previously (possibilities include the Franciscan Complex, CA,
USA, and Syros Greece), and other locales of interest. Analytical work will
be undertaken in the MAGIC Lab
Geochemistry and Isotope Characterization Laboratory) and the electron beam
facilities https://umaine.edu/earthclimate/facilities/ in the School of
Earth and Climate Sciences at the University of Maine. To inquire please
email email@example.com. Start date is January, 2022.
Dr. Alicia Cruz-Uribe (she/her/hers)
Edward Sturgis Grew Associate Professor of Petrology and Mineralogy
Graduate Coordinator, School of Earth and Climate Sciences
Co-chair, Women in STEMM (WiSTEMM) Oversight Committee
University of Maine
5790 Bryand Global Sciences Center
Orono, ME 04469
Dear American Mineralogist Readers,
Below are the Paper Highlights for this month’s issue of the American Mineralogist: International Journal of Earth and Planetary Materials. You may also view the American Mineralogist Paper Highlights list at here (http://www.minsocam.org/MSA/Ammin/AM_NotableArticles.html).
The DOI links below will take you to the abstract on GeoScienceWorld.
If you have “IP” access via your institution’s library, it should reveal the whole paper. Consult your institution’s IT department or friendly librarian.
If you have MSA membership, then authenticate in from the American Mineralogist menu (herehttp://www.msapubs.org/ directly). Once at the portal page, click the right-side American Mineralogist link, enter your user name (e-mail address), and your password (membership number). Then search via your browser’s search tools for the paper you want to read. (On Rachel’s computer, it is control-f but we think that is little different for everyone.)
Note that on GSW you can sign up for a table of contents to be sent you when the issue is live -- this is a feature open to anyone who registers on the site.
Thank you for reading American Mineralogist.
Stable and transient isotopic trends in the crustal evolution of Zealandia Cordillera
Schwartz et al. use zircon δ18O and Lu-Hf isotope analyses to explore the interplay between spatial and temporal magmatic signals in the Mesozoic Zealandia Cordillera. They find that Mesozoic pluton chemistry was controlled by both crustal/upper mantle architecture and a transient process involving a mantle-controlled flare-up event that involved mantle melts contaminated with recycled sediments. Their data demonstrate that spatial and temporal signals are intimately linked, and when evaluated together they provide important insights into the role of stable and transient arc magmatic trends in Cordilleran batholiths.
An evolutionary system of mineralogy, Part V: Aqueous and thermal alteration of planetesimals (~4565 to 4550 Ma)
The evolutionary system of mineralogy classifies minerals based on their roles in planetary evolution. The first five parts of the system summarize all known minerals that emerged prior to the formation of planet Earth. Most of those minerals are preserved in the meteorites that still fall to Earth today. In Part V, by Hazen and Morrison, the focus is on the varied secondary minerals that formed in planetesimals more than 4.5 billion years ago through the often linked processes of aqueous alteration and thermal metamorphism. In this contribution Hazen and Morrison catalog 166 secondary meteorite minerals, including the earliest known appearances of species with the chemical elements Co, Ge, As, Nb, Ag, Sn, Te, Au, Hg, Pb, and Bi. Among the varied secondary meteorite minerals are the earliest known examples of halides, arsenides, tellurides, sulfates, carbonates, hydroxides, and a wide range of micas and clay minerals.
Cr2O3 in Corundum: Ultra-high contents under reducing conditions
Griffin et al. describe a suite of corundum xenocrysts in Cretaceous, mafic, pyroclastic rocks on Mt Carmel, Israel, which includes rubies with the highest recorded contents of Cr2O3. Many coexist with K- and Na-beta alumina phases and native chromium, requiring extremely reducing conditions, indicating oxygen fugacities circa 5 log units below the Iron-Wustite buffer. Zoning patterns indicate a progressive decrease in oxygen fugacity during crystallization (Fig. 1), which is interpreted as tracking the interaction of oxide melts with mantle-derived methane and hydrogen near the crust-mantle boundary.
Plagioclase population dynamics and zoning in response to changes in temperature and pressure
In this paper by Andrews, the numerical model SNGPlag tracks the numbers, sizes, morphologies, and compositional zoning of plagioclase crystals through time in response to changes in magmatic conditions. Low growth rates and dissolution result in significant fractions of time (>>50%) missing from the final crystal record. Growth of complexly zoned phenocrysts requires the addition of new magma. Crystal records are biased towards more recent intervals and periods of decreasing temperature. Crystallization (or dissolution) acts to return magmas to near-equilibrium crystal fractions within hundreds of days.
Limited channelized fluid infiltration in the Torres del Paine contact aureole
This paper by Siron et al. describes the metamorphic evolution of the Torres del Paine contact aureole that experienced a limited amount of fluid infiltration from the crystallizing granite. This evolution was tracked using hydrogen and oxygen isotopes and Cl concentrations in biotite. The potential of these different tracers to track fluid-rock interactions is evaluated and highlights the sensitivity of hydrogen vs. oxygen isotopes for such use. Cl content in biotite is also a promising tool for such work.
Quantitative determination of the shock stage of L6 ordinary chondrites using X-ray diffraction
The mean lattice strain and grain size factor for olivine and orthopyroxene of 14 L6 chondrites were determined by Imae and Kimura from analyses based on Williamson-Hall plots via X-ray diffraction. The combination of mean lattice strain with grain size factor enables the construction of a shock barometer.
A new method to rapidly and accurately assess the mechanical properties of geologically relevant materials
This new method by Deng et al. will enable geological scientists and engineers to rapidly determine the elastic behavior of any rock or mineral in a simple manner with a robust statistical response. It will also facilitate the determination of elastic properties of rocks and minerals as a function of composition, structure, hydration, or other physical variables. This will undoubtedly impact the development of geologic-based deformation models through knowledge of the constituent material properties for validation and prediction accuracy.
Two-stage magmatism and tungsten mineralization in the Nanling Range, South China: Evidence from the Jurassic Helukou deposit
In this study, Cao et al. report LA-ICP-MS zircon U-Pb and molybdenite Re-Os ages of the Helukou W deposit, which is a representative W deposit located in the Guposhan district, SW of Nanling Range, South China. This geochronological data aims to reveal persistent (Early to Jurassic) granitic magmatism and related W-Sn mineralization events in the Nanling region. In addition, the in-situ trace element and Sr isotopes compositions of scheelite from the skarn- and altered granite-type ores of the Helukou W deposit are reported, with the purpose of outlining the nature of the ore-forming fluids in the long-lived magmatic-hydrothermal system. The data reveals two stages of magmatism and tungsten mineralization in the Guposhan ore field during Early Jurassic (~180 Ma) and Middle Jurassic (~165 Ma). This 20 m.y. long-lived successive magmatism and mineralization in the Nanling Range will provide new insights into the magmatism, mineralization, and metallogenesis in this region.
Constraints on scheelite genesis at the Dabaoshan stratabound polymetallic deposit, South China
Stratabound polymetallic deposits serve as one of the most important reserves of base metals in South China, but the genetic relationship between stratabound base metal mineralization and porphyry mineralization remains in dispute. Scheelite occurs as a characteristic mineral in many stratabound polymetallic deposits and in the adjacent porphyry system. In this paper, Su et al. use scheelite geochemistry, zircon, and hydrothermal apatite U-Pb dating to constrain the genesis of scheelite in stratabound orebodies at Dabaoshan. By integrating scheelite CL textures, trace element characteristics, and the new dating results, they demonstrate that ore-forming fluids responsible for scheelite formation in stratabound orebodies were derived from the Dabaoshan porphyry system. Furthermore, Jurassic porphyry mineralization at least partially contributed to Cu mineralization in the stratabound orebodies. This work suggests that scheelite geochemistry, combined with geochronology studies, can contribute to our understanding of stratabound orebody genesis.
Crystal chemistry of schreibersite, (Fe,Ni)3P
Schreibersite is the most common phosphide mineral and the main carrier of reduced phosphorus in the celestial bodies. The present paper by Britvin et al. reports on previously obscured trends in Fe and Ni distribution across schreibersite structures, which are directly related to crystallization histories of metal-rich planetary interiors.
Elastic geobarometry: how to work with residual inclusion strains and pressures
Gilio et al. discuss the difference between various approaches to retrieve the residual pressures and residual strains from Raman measurements of inclusions. They provide general guidelines on how to deal with inclusion strain, measurements, inclusion pressure, and their uncertainties.
Controls on tetrahedral Fe(III) abundance in 2:1 phyllosilicates - - Discussion
Controls on tetrahedral Fe(III) abundance in 2:1 phyllosilicates - Reply
New Mineral Names
Book Review: Geochronology and Thermochronology