--> Testing the Mojave-Snow Lake fault hypothesis using Laser-induced Breakdown Spectroscopy

AAPG Pacific Section and Rocky Mountain Section Joint Meeting

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Testing the Mojave-Snow Lake fault hypothesis using Laser-induced Breakdown Spectroscopy

Abstract

While several studies have been conducted, many questions regarding the existence of the Mojave-Snow Lake fault remain. The Mojave-Snow Lake fault is an inferred right lateral strike slip fault without a discrete fault trace that has been hypothesized to have displaced passive margin rocks of the Snow Lake block from the vicinity of Victorville, California, 400 kilometers to the central Sierra Nevada batholith to the north (Lahren and Schweickert, 1990). These displaced passive margin rocks of the Death Valley facies comprise a variety of metasedimentary rocks including quartzites, metapelites and carbonates. Correlations of possible rock units displaced by the proposed fault have also been made through detrital zircon age dates (Grasse et al., 2001; Memeti et al., 2010). Chapman et al. (2015) supply evidence that argues for the possible reactivation of the Last Chance thrust sequence and 65 kilometers of displacement of passive margin strata from the east. Chapman's et al. (2015) hypothesis thus contradicts early studies on the area, which have only suggested north-south strike slip movement (Lahren and Schweickert, 1990; Grasse et al., 2001). While detrital zircon age dating has provided strong age correlations between passive margin units of the Death Valley facies and the Snow Lake block, it is not clear where from the north-south extensive passive margin the Snow Lake block may have been derived from. We are thus conducting geochemical analysis of heavy minerals from both the displaced rock units and passive margin strata to further test the Mojave Snow lake fault hypothesis. Laser-induced breakdown spectroscopy (LIBS) can provide a detailed chemical signature through elemental analysis (McMillan et al., 2014). We hypothesize that LIBS is capable of comparing the proposed stratigraphic correlations and test the conclusions made from data collected by previous studies. If LIBS detects strong similarities between specific locations from the passive margin with the Snow Lake block pendants, more detail can be determined on the exact location the Snow Lake block strata were derived from, and help determine the existence and amount of displacement of the Mojave-Snow Lake fault. We will present preliminary data and interpretations collected and discuss further steps in regards to the methodology.