Date of Award

Summer 8-13-2021

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Earth Sciences

Advisor

Alicia Cruz-Uribe

Second Committee Member

Martin Yates

Third Committee Member

Chunzeng Wang

Additional Committee Members

David Lentz

Abstract

The Pickett Mountain deposit is a volcanogenic massive sulfide (VMS) base-metal deposit located 15 miles north of Patten, ME. The deposit, discovered in 1979, was abandoned in 1989. The deposit remained abandoned until 2017, when Wolfden Mt. Chase LLC purchased the land for further development after Maine mining regulations changed. This project is a collaboration between the University of Maine, the University of Maine – Presque Isle, Wolfden Resources Corp., and the University of New Brunswick to better understand the regional and deposit-scale geology related to the deposit to fill in gaps of the geologic story of northern Maine as well as potentially guide massive sulfide exploration around Pickett Mountain and the state of Maine.

Located in the southeast limb of the Weeksboro-Lunksoos Lake Belt (WLLB) of northern Maine the deposit is a part of the broader Ordovician Northern Maine Volcanic Belt (NMVB). Field mapping, drill core examination, and petrographic analysis confirm and add to the knowledge of how the various pyroclastic, igneous, and sedimentary rock units are correlated. The deposit host stratigraphy is composed of Cambrian Grand Pitch sedimentary rocks overlain by Ordovician pyroclastic and igneous rocks that are interpreted to be an extension of the Ganderian basement and Peri-Gondwanan arc-back-arc inliers that make up the Gander Terrane, which hosts the world-class VMS district, the Bathurst Mining Camp (BMC), auguring well for the economic potential Maine.

Whole-rock lithogeochemistry helps further characterize and differentiate the altered pyroclastic host rocks; whole-rock concentrations and ratios of selected immobile elements were used from 35 drill holes around the deposit to accomplish this. The volcanic host rocks have transitional-tholeiitic magmatic affinities and volcanic-arc- extensional tectonic affinities, consistent with the deposit forming within a continental back-arc basin. Immobile element ratios (Zr/TiO2, Y/TiO2, TiO2/Al2O3, and Zr/Al2O3), are used to differentiate the stratigraphy into three, otherwise undetectable, chemostratigraphic units.

Several drill holes from the Pickett Mountain deposit were selected for detailed, systematic portable X-ray fluorescence (pXRF) analysis to assess the capability of the technology to serve as a reliable and cost/time effective alternative to conventional methods of geochemical data acquisition. Results, though limited by the absence of Y, are consistent with those from the whole-rock lithogeochemical data and prove the technology is a reliable tool for exploration.

Zircon U-Pb analysis using LA-ICP-MS method was performed on two samples, collected from the footwall and hanging wall of the deposit. Results yielded weighted mean 206Pb/238U ages of 485 ± 2 Ma for a footwall felsic quartz-crystal lapilli tuff sample and 481 ± 3 Ma for a hanging wall rhyolite sample, proving to be around 12 my older than the only other age obtained from the WLLB (467 ± 5 Ma; Ayuso et al., 2003).

The stratigraphy, lithogeochemistry, and geochronology of this study adds to the understanding of Maine’s geology and potential for VMS mineral resources. Use and assessment of pXRF proves the method as a cost-effective and reliable lithogeochemistry alternative in this ongoing process of illuminating pieces to the puzzle of Maine’s geology and exploration for mineral resources.

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