Multiple abiotic and biotic factors combine in nature to influence the formation of calcium carbonate limestone deposits. Systems Geobiology studies of how micro-organisms respond to, or sometimes even control, the coupled effects of environmental change and mineralization will permit more accurate interpretation of the fossil record of ancient microbial life. Mammoth Hot Springs in Yellowstone National Park, USA, serves as a natural laboratory for tracking how the dynamic interplay of physical, chemical and biological factors come together to form hot-spring limestone (called ‘travertine’). Systematic downstream correlations occur at Mammoth Hot Springs between travertine deposition (geomorphology, crystalline structure and geochemistry), microbial communities (mat morphology, pigmentation, and phylogenetic and metabolic diversity) and spring-water conditions (temperature, pH, geochemistry and flow). Field-based microscale and mesoscale experimentation indicates that microbes directly influence travertine growth rate and crystalline structure. At the macroscale, time-lapse field photography and numerical modelling suggest that travertine terrace geomorphology is influenced strongly by hydrology, heat dispersion and geochemistry. These results from Mammoth Hot Springs allow establishment of a conceptual framework across broad spatial and temporal scales in which to track how multiple geological and biological factors combine to control CaCO3 crystal precipitation and the resulting formation of travertine deposits.

Hot‐spring Systems Geobiology: abiotic and biotic influences on travertine formation at Mammoth Hot Springs, Yellowstone National Park, USA

The Yellowstone Plateau Volcanic Field is characterized by extensive seismicity, episodes of uplift and subsidence, and a hydrothermal system that comprises more than 10,000 thermal features, including geysers, fumaroles, mud pots, thermal springs, and hydrothermal explosion craters. The diverse chemical and isotopic compositions of waters and gases derive from mantle, crustal, and meteoric sources and extensive water-gas-rock interaction at variable pressures and temperatures. The thermal features are host to all domains of life that utilize diverse inorganic sources of energy for metabolism. The unique and exceptional features of the hydrothermal system have attracted numerous researchers to Yellowstone beginning with the Washburn and Hayden expeditions in the 1870s. Since a seminal review published a quarter of a century ago, research in many fields has greatly advanced our understanding of the many coupled processes operating in and on the hydrothermal system. Specific advances include more refined geophysical images of the magmatic system, better constraints on the time scale of magmatic processes, characterization of fluid sources and water-rock interactions, quantitative estimates of heat and magmatic volatile fluxes, discovering and quantifying the role of thermophile microorganisms in the geochemical cycle, defining the chronology of hydrothermal explosions and their relation to glacial cycles, defining possible links between hydrothermal activity, deformation, and seismicity; quantifying geyser dynamics; and the discovery of extensive hydrothermal activity in Yellowstone Lake. Discussion of these many advances forms the basis of this review.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/2014RG000452

Dynamics of the Yellowstone hydrothermal system

The study of gas emission rates, chemistry and isotopic analyses show that the rate of helium-4 emission from the crust at Yellowstone is orders of magnitude greater than any conceivable rate of generation within the crust; this implies that helium has accumulated for hundreds of millions of years in deeper Archaean cratonic rocks, only to be liberated over the past two million years by crustal metamorphism induced by the Yellowstone hotspot. Yellowstone National Park is well known for its geysers and hot-spring waters, the surface manifestation of a volcanic hotspot. Helium is commonly used as a tracer by geoscientists, tracking degassing from the mantle, dating groundwater and timing the rise of continents. This study combines gas emission rate data with chemistry and isotopic analyses to show that crustal helium-4 emission rates from Yellowstone exceed by orders of magnitude any conceivable rate of generation within the crust. They conclude that helium has accumulated for at least hundreds of millions of years in Archaean cratonic rocks beneath Yellowstone, only to be liberated during the past two million years by intense crustal metamorphism induced by the Yellowstone hotspot. Helium is used as a critical tracer throughout the Earth sciences, where its relatively simple isotopic systematics is used to trace degassing from the mantle, to date groundwater and to time the rise of continents1. The hydrothermal system at Yellowstone National Park is famous for its high helium-3/helium-4 isotope ratio, commonly cited as evidence for a deep mantle source for the Yellowstone hotspot2. However, much of the helium emitted from this region is actually radiogenic helium-4 produced within the crust by α-decay of uranium and thorium. Here we show, by combining gas emission rates with chemistry and isotopic analyses, that crustal helium-4 emission rates from Yellowstone exceed (by orders of magnitude) any conceivable rate of generation within the crust. It seems that helium has accumulated for (at least) many hundreds of millions of years in Archaean (more than 2.5 billion years old) cratonic rocks beneath Yellowstone, only to be liberated over the past two million years by intense crustal metamorphism induced by the Yellowstone hotspot. Our results demonstrate the extremes in variability of crustal helium efflux on geologic timescales and imply crustal-scale open-system behaviour of helium in tectonically and magmatically active regions.

Prodigious degassing of a billion years of accumulated radiogenic helium at Yellowstone

Hyperspectral imaging has been used in a variety of geological applications since its advent in the 1970s. In the last few decades, different techniques have been developed by geologists to analyze hyperspectral data in order to quantitatively extract geological information from the high-spectral-resolution remote sensing images. We attempt to review and update various steps of the techniques used in geological information extraction, such as lithological and mineralogical mapping, ore exploration, and environmental geology. The steps include atmospheric correction, dimensionality processing, endmember extraction, and image classification. It is identified that per-pixel and subpixel image classifiers can generate accurate alteration mineral maps. Producing geological maps of different surface materials including minerals and rocks is one of the most important geological applications. The hyperspectral images classification methods demonstrate the potential for being used as a main tool in the mining industry and environmental geology. To exemplify the potential, we also include a few case studies of different geological applications.

/pdf/hyperspectral-remote-sensing-in-lithological-mapping-mineral-1rww7700i8.pdf

Hyperspectral remote sensing in lithological mapping, mineral exploration, and environmental geology: an updated review

The sulfur isotope evolution of magmatic-hydrothermal fluids: insights into ore-forming processes

Hydrothermal Processes Above the Yellowstone Magma Chamber: Large Hydrothermal Systems and Large Hydrothermal Explosions

In this chapter, the intent is to summarize the results of traditional stable isotope studies (mainly H, B, O, C, and S) that have greatly contributed to the understanding of ore-forming processes over the last 60 years and to provide an up-to-date assessment of the application of new nontraditional isotope systems (Fe, Cu, Zn, Se, Mo, Hg, and Tl).

13.3 – Stable Isotope Geochemistry of Mineral Deposits

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/pdf/gas-and-isotope-chemistry-of-thermal-features-in-yellowstone-b8cz7ta6gl.pdf

Gas and isotope chemistry of thermal features in Yellowstone National Park, Wyoming

. HOTSPOT is an international collaborative effort to understand the volcanic history of the Snake River Plain (SRP). The SRP overlies a thermal anomaly, the Yellowstone-Snake River hotspot, that is thought to represent a deep-seated mantle plume under North America. The primary goal of this project is to document the volcanic and stratigraphic history of the SRP, which represents the surface expression of this hotspot, and to understand how it affected the evolution of continental crust and mantle. An additional goal is to evaluate the geothermal potential of southern Idaho. Project HOTSPOT has completed three drill holes. (1) The Kimama site is located along the central volcanic axis of the SRP; our goal here was to sample a long-term record of basaltic volcanism in the wake of the SRP hotspot. (2) The Kimberly site is located near the margin of the plain; our goal here was to sample a record of high-temperature rhyolite volcanism associated with the underlying plume. This site was chosen to form a nominally continuous record of volcanism when paired with the Kimama site. (3) The Mountain Home site is located in the western plain; our goal here was to sample the Pliocene-Pleistocene transition in lake sediments at this site and to sample older basalts that underlie the sediments. We report here on our initial results for each site, and on some of the geophysical logging studies carried out as part of this project. doi: 10.2204/iodp.sd.15.06.2013

/pdf/first-results-from-hotspot-the-snake-river-plain-scientific-2pkv4222nw.pdf

First Results from HOTSPOT: The Snake River Plain Scientific Drilling Project, Idaho, U.S.A.

http://www.rcn.montana.edu/Publications/Pdf/2005/1_3Shanks.pdf

W.C. Pat Shanks

Papers

Hydrothermal Processes Above the Yellowstone Magma Chamber: Large Hydrothermal Systems and Large Hydrothermal Explosions

13.3 – Stable Isotope Geochemistry of Mineral Deposits

Gas and isotope chemistry of thermal features in Yellowstone National Park, Wyoming

First Results from HOTSPOT: The Snake River Plain Scientific Drilling Project, Idaho, U.S.A.

Hydrothermal vent fluids, siliceous hydrothermal deposits, and hydrothermally altered sediments in Yellowstone Lake