首页|Extending classical geochemical weathering studies through the mountain block: The effect of increasing scale on geochemical evolution in the Sierra Nevada (CA)

Extending classical geochemical weathering studies through the mountain block: The effect of increasing scale on geochemical evolution in the Sierra Nevada (CA)

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  • NSTL
  • Elsevier
The seminal studies of Feth et al. (1964) and Garrels and Mackenzie (1967) describe the chemical weathering processes controlling the geochemistry of spring waters in the Sierra Nevada (CA) and provide a framework for understanding geochemical weathering processes at local groundwater scales (i.e., short distances between recharge and subsequent groundwater discharge). Here, we extend these concepts to investigate the factors controlling geochemical evolution at the intermediate, mountain-block scale (i.e., increased flowpath length, circulation depth, and rock-water interaction). We accomplish this by applying a multi-tracer approach to mountain-front springs emerging along the Sierra Nevada frontal fault zone in Owens Valley, CA. These springs emerge at a significantly lower elevation (1100-2000 mamsl) than the eastern Sierra crest (4000+ mamsl) and provide a window into the hydrogeological and hydrochemical processes occurring within the mountain block from high-elevation mountain-block recharge to low-elevation mountain-front discharge, a recognized knowledge gap in hydrogeology. We delineate approximate spring contributing areas and identify geologic units likely sourcing springflow using stable isotopes of water and dissolved noble gases. We then classify four major geochemical groups after identifying the likely geologic units sourcing springflow and subsequent analysis and modeling of spring geochemistry. Our results lead to three main conclusions: 1) geochemical evolution within the mountain block from high elevation mountain block weathering to mountain front discharge follows power-law weathering relationships and becomes increasingly dependent on the dissolution of disseminated calcite present in plutonic rocks with increasing flowpath length, 2) geologic heterogeneity (i.e., differences in plutonic compositions and the presence/absence of Paleozoic metasedimentary roof pendants) exerts a dominant control on geochemical evolution with increased flowpath length, and 3) within geochemical groups, simple metrics like TDS or mole transfers from inverse geochemical models scale with physical and isotopic indicators of groundwater circulation and flowpath length.

Geochemical evolutionMountain front springsGranite weatheringSierra NevadaExcess calciumNOBLE-GASESGROUNDWATER-FLOWMICROTUS-CALIFORNICUSDISSEMINATED CALCITESOLUTE CHEMISTRYGRANITOID ROCKSWATER CHEMISTRYTHERMAL WATERSRESIDENCE TIMESILICATE ROCKS

Meyers, Zachary P.、Rademacher, Laura K.、Frisbee, Marty D.、Warix, Sara R.

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Univ Pacific

Purdue Univ

Colorado Sch Mines

2022

10.1016/j.chemgeo.2022.120831

Chemical geology

Chemical geology

EISCI
ISSN：0009-2541
年,卷(期)：2022.598
  • 96