Detangling Primary and Secondary Signatures

Early Earth

Siliceous rocks are one of the most promising deep time preservation agents – they encapsulate the earliest putative micro-fossils and microbial communities and preserve the world’s oldest known bio-signatures.

However, the depositional environment and conditions of formation for these archival silica-rich precipitates are often in dispute. They form at the intersection of hydrothermal and sedimentary processes, making their intricate diagenetic and alteration histories difficult to decipher. Our lab has several projects that combine textural and geochemical tools to investigate fundamental questions that link to how Precambrian silica-rich rocks form.

To interpret primary features in Precambrian rocks, we must first determine the metamorphic and diagenetic history.

Our lab specializes in mineral paragenesis in Precambrian sedimentary and hydrothermal rocks with an emphasis on sedimentary petrology and micro-analytical geochemical techniques. We have several on-going projects in Archean greenstone belt terranes as well as Proterozoic sedimentary basins, enhanced by our regional connection to the Precambrian.

Recent graduate Sam Duncanson presented about diagenetic reactions in Paleoproterozoic iron formation at the virtual North-Central GSA section meeting (May 2020).

You can view Sam’s presentation here! >

Want to learn more about our work on Early Earth systems?

Check out these references:

(1) Textural, geochemical, and isotopic data from silicified rocks and associated chemical sedimentary rocks in the ~ 2.7 Ga Abitibi greenstone belt, Canada: Insight into the role of silicification

(2) Development of a mixed seawater-hydrothermal fluid geochemical signature during alteration of volcanic rocks in the Archean (∼2.7 Ga) Abitibi Greenstone Belt, Canada

(3) Micro-scale silicon isotope heterogeneity observed in hydrothermal quartz precipitates from the >3.7 Ga Isua Greenstone Belt, SW Greenland

(4) A New Depositional Framework for Massive Iron Formations After the Great Oxidation Event

(5) Revised Provenance, Depositional Environment, and Maximum Depositional Age for the Baraboo (<​ca. 1714 Ma) and Dake (<​ca. 1630 Ma) Quartzites, Baraboo Hills, Wisconsin

Geochemical Windows to the Past

Modern Analogs

We collaborate with experts in modern hydrothermal systems.

Working in Precambrian terranes, we often utilize indirect approaches and work backwards to answer questions about ancient seawater or habitability on a nascent planet.

We are fortunate to collaborate with researchers that work in hot springs at Yellowstone National Park to better understand processes of silicification, and preservation/ alteration of biogeochemical signals in modern hydrothermal systems.

Such modern systems may serve as a geochemical window to the past. For instance, hot springs with vastly different pH and temperature provide the opportunity to directly test the behavior deep time elemental and isotope proxies. We can also compare textural and mineralogical attributes of altered rocks from modern hydrothermal systems, to identify element mobility, changes in mineralogy, and associated reactions. We can then apply this modern alteration framework to observations from deep time systems, while keeping in mind key differences in atmospheric composition and planetary redox states of the past.


Community connections

Our lab is dedicated to connecting with our local K-12 programs and broader community.
We have developed several outreach projects since the lab started in Fall 2015 and we remain committed to this goal. (Check back soon for our shared resources).
We recently had a funded project: “Involving UMD students across campus to update the museum-quality display cases in Heller Hall and connect to a modern audience.”
Project goal – The goal of this project is to involve UMD students from across campus in the re-design and renovation of the outdated museum-quality display cases on the first floor of Heller Hall.
Purpose – By updating the Heller Hall museum cases, we propose to bring the displays into the digital age and increase accessibility of the information for diverse audiences within our community. In re-designing the cases within an updated scientific framework, our goals are to improve: (1) science communication; (2) the connection between science and art; (3) diversity and accessibility of the displays.
Community impact – With the renovation we have the unique opportunity to increase public engagement with UMD by providing a free, accessible educational resource for classes, students, and the public.