B. D. Rodriguez
J. L. Wooden
V. J. S. Grauch
2003
<p><span>We combined information from Sr and Pb isotope data and magnetotelluric models to develop a new magnetic and gravity interpretation of the </span>crustal<span> </span>structure<span> of </span>north<span>-</span>central<span> </span>Nevada<span> to better understand the origin of </span>mineral<span> </span>trends<span>. The new interpretation suggests a </span>crustal<span> </span>structure<span> that is composed of Precambrian continental crust, transitional crust, and primarily oceanic crust that are separated by northwest- and northeast-striking fault zones. The magnetic expression of the buried Precambrian continental crust is recognized for the first time. Low magnetic values primarily reflect magnetite-poor crystalline crust rather than elevated temperatures at depth. Northwest- and northeast-striking </span>crustal<span> boundaries are defined by </span>isotopic<span> data and abrupt gradients </span>in<span> gravity and magnetic data. The Carlin and Battle Mountain-Eureka </span>mineral<span> </span>trends<span> are associated with two of three northwest-striking boundaries. The Carlin boundary is primarily defined by a change </span>in<span> density and </span>isotopic<span> character of the lower to middle crust. The Battle Mountain-Eureka boundary coincides with a density contrast </span>in<span> the upper crust and a change </span>in<span> </span>isotopic<span> character </span>in<span> the lower to middle crust. Magnetotelluric models suggest that the Battle Mountain-Eureka boundary represents a </span>crustal<span> fault zone for most of its extent, but that deep-rooted faulting is more complex near and northwest of Battle Mountain. </span>Crustal<span> fault zones inferred from the magnetotelluric models near the Carlin </span>trend<span> are oblique to it, suggesting that they may not have been controlled by the deep boundary seen </span>in<span> the gravity and </span>isotopic<span> data. The third northwest-trending boundary is </span>related<span> to the western edge of the buried Precambrian continent </span>in<span> west-</span>central<span> </span>Nevada<span>, but lacks an associated </span>mineral<span> </span>trend<span>. A northeast-striking boundary forms the northern limit of Precambrian continental and transitional crust. The boundaries may have originated as rift or transform faults during Precambrian breakup of Rodinia or as faults accommodating lateral movements or accretion during later Paleozoic </span>tectonic<span> events. Comparing the </span>crustal<span> </span>structure<span> to </span>tectonic<span> elements produced by successively younger events shows that it had a profound influence on subsequent sedimentation, deformation, magmatism, extension, and most important, mineralization.</span></p>
application/pdf
10.2113/gsecongeo.98.2.269
en
Society of Economic Geologists
Geophysical and isotopic constraints on crustal structure related to mineral trends in north-central Nevada and implications for tectonic history
article