Layered intrusions in the Precambrian: Observations and perspectives

Smith, William D., Jenkins, M. Christopher, Augustin, Claudia T., Virtanen, Ville J., Vukmanovic, Zoja ORCID: https://orcid.org/0000-0001-7559-0023 and O'Driscoll, Brian (2024) Layered intrusions in the Precambrian: Observations and perspectives. Precambrian Research, 415. ISSN 0301-9268

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Abstract

Layered intrusions are plutonic bodies of cumulates that form by the crystallization of mantle-derived melts. These intrusions are characterized by igneous layering distinguishable by shifts in mineralogy, texture, or composition. Layered intrusions have been fundamental to our understanding of igneous petrology; however, it is their status as important repositories of critical metals – such as platinum-group elements, chromium, and vanadium – that has predominantly driven associated research in recent decades. Many layered intrusions were emplaced during the Precambrian, predominantly at the margins of ancient cratons during intervals of supercontinent accretion and destruction. It appears that large, layered intrusions require rigid crust to ensure their preservation, and their geometry and layering is primarily controlled by the nature of melt emplacement. Layered intrusions are best investigated by integrating observations from various length-scales. At the macroscale, intrusion geometries can be discerned, and their presence understood in the context of the regional geology. At the mesoscale, the layering of an intrusion may be characterized, intrusion-host rock contact relationships studied, and the nature of stratiform mineral occurrences described. At the microscale, the mineralogy and texture of cumulate rocks and any mineralization are elucidated, particularly when novel microtextural and mineral chemical datasets are integrated. For example, here we demonstrate how mesoscale observations and microscale datasets can be combined to understand the petrogenesis of the perplexing snowball oiks outcrop located in the Upper Banded Series of the Stillwater Complex. Our data suggest that the orthopyroxene oikocrysts did not form in their present location, but rather formed in a dynamic magma chamber where crystals were transported either by convective currents or within crystal-rich slurries. Critical metals may be transported to the level of a nascent intrusion as dissolved components in the melt. Alternatively, ore minerals are entrained from elsewhere in a plumbing system, potentially facilitated by volatile-rich phases. There are many ore-forming processes propounded by researchers to occur at the level of emplacement; however, each must address the arrival of the ore mineral, its concentration of metals, and its accumulation into orebodies. In this contribution, several of these processes are described as well as our perspectives on the future of layered intrusion research.

Item Type:	Article
Additional Information:	Data availability statement: Data are available in the supplementary materials. Requests for the raw EBSD and element map data can be made to the authors. Funding information: V.J.V is supported by the SEMACRET project (101057741) co-funded by Horizon Europe program and UK Research Innovation. M.C.J. is supported by the U.S. Geological Survey’s Mineral Resource Program. W.D.S. is presently supported by a CSIRO Early Research Career Postdoctoral Fellowship. BO’D acknowledges current research support from the Natural Sciences and Engineering Research Council of Canada (NSERC Discovery Grant) and from the Newmont Chair in Economic Geology (University of Ottawa).
Faculty \ School:	Faculty of Science > School of Environmental Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Geosciences
Depositing User:	LivePure Connector
Date Deposited:	19 Nov 2024 17:30
Last Modified:	02 Dec 2024 01:45
URI:	https://ueaeprints.uea.ac.uk/id/eprint/97727
DOI:	10.1016/j.precamres.2024.107615

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