75-22 Unmapped Units of the Tinton Dome: Revisiting the Tertiary Intrusions of the Northern Black Hills, South Dakota
Session: Mineralogy, Geochemistry, Petrology, and Volcanology Student Session (Posters)
Poster Booth No.: 315
Presenting Author:
Dylan Jacob Chase, Student, Researcher, InternAuthors:
Chase, Dylan Jacob1, Domagall, Abigail2, Schilling, Jill3(1) School of Natural Sciences, Black Hills State University, Spearfish, South Dakota, USA, (2) School of Natural Sciences, Black Hills State University, Spearfish, South Dakota, USA, (3) School of Natural Sciences, Black Hills State University, Spearfish, South Dakota, USA,
Abstract:
A 85 km by 40 km linear region of alkali igneous intrusions run through the northern Black Hills of South Dakota and Wyoming trending N70°W from Devils Tower in the west to Bear Butte in the east. Past geochronology data puts these intrusions at ~40-60 Ma (Tertiary), with the younger intrusions to the west. Research has typically focused on the mineral resources of these intrusions: hydrothermal activity associated with the magmas caused remobilization of gold. Less research has focused on the magma sources for these intrusions and the tectonic environment associated with them. A large amount of petrographic and geochemical data exists however, these are not readily inaccessible, and a repository of these data would benefit deeper understanding of the area. Additionally, while the larger intrusive centers (such as the Lead-Deadwood dome, and the Tinton dome) have been heavily researched there are smaller, unmapped outcrops that will add to our dataset and understanding. Our goal is to compile the pre-existing data into an open access GIS layer, and to add to the data by identifying and classifying new, unmapped outcrops. Preliminary field work has identified five unmapped, small (<2 km exposure) outcrops surrounding the Tinton area of the northern hills. Hand samples are dark gray, aphanitic-aphyric to aphanitic-porphyritic and suggest the outcrops are lower in silica, and are later-stage intrusions (based on xenolith inclusions). Petrographic thin sections, and geochemistry data analysis, will provide more accurate mineralogy and classification. This research is actively ongoing, and will continue with reconnaissance to identify more unmapped units, and gathering pre-existing data into one GIS database.
Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025
© Copyright 2025 The Geological Society of America (GSA), all rights reserved.
Unmapped Units of the Tinton Dome: Revisiting the Tertiary Intrusions of the Northern Black Hills, South Dakota
Category
Topical Sessions
Description
Session Format: Poster
Presentation Date: 10/19/2025
Presentation Room: Hall 1
Poster Booth No.: 315
Author Availability: 3:30–5:30 p.m.
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