Utilizing Paleomagnetic Evidence to Constrain the Timing of Magnetization of Zebra Dolomite across the Great Basin, Nevada

Abstract

Hydrothermal zebra dolomites are a distinct carbonate rock characterized by alternating bands of hydrothermal saddle dolomite (white) layers and darker dolomite layers, typically millimeter thicknesses. The zebra dolomites are often associated with ore mineralization, and are typically described as forming at the same time as the ore laden hydrothermal fluids migrated through the host dolomites. This study uses paleomagnetic techniques to determine if the zebra dolomites hold stable magnetizations that can be used to determine the age of the zebra dolomite formation. These hydrothermal zebra dolomites sampled for this study are hosted in carbonate rocks of Cambrian, Devonian, Mississippian, and Permian age in the eastern part of the Basin and Range Province, Nevada. Of the nine sample locations, six contained characteristic remanent magnetizations (ChRMs) that are interpreted as CRMs held in magnetite based on unblocking temperatures from 360-580ºC. One site had visible reddening, and its ChRM had unblocking temperatures in the range of 540-660 ºC, indicative of maghemite. Twelve CRMs were observed in zebra dolomites across sample localities (some sites held multiple ChRMs). Ten of the twelve CRMs plot on the North American Polar Wander Path (APWP). The CRMs vary in age from Silurian to Jurassic. These multiple ages of magnetization acquisitions reflect the complex tectonic history of Nevada. More sampling of the unaltered non-zebra host rock is needed to determine if these CRMs are localized within the zebra or more widespread. The CRMs are interpreted to date differing fluid pulse conduits over multiple orogenic events throughout the Paleozoic.