Serpentinites, Silica-Carbonate Alteration, and Mercury Ore Deposits in Coast Range California: Implications for the Deep Hydrology of the California Coast Ranges and the Deep Hydrology of the San Andreas Fault System
Abstract
Numerous geological reports have described field relations of surface exposures of serpentinite indicative of serpentinite intrusions into host rocks including the Franciscan along the California coastal margin at T < 500°C, some during Neogene time (see Kellner and Kirby AGU Poster). Frequently associated with many of these serpentinite bodies are later-stage silica-carbonate alteration and epithermal mercury mineralization. These later hydrothermal processes can be explained as a consequence of shallow-level reactions of carbonated water with serpentine (Knopf, 1906; Barnes et al., 1973; White, 1967; Rytuba, 1986) (See also the Rytuba, Kirby, and Kellner AGU poster). These hydrothermal deposits require a flux of such fluids from depth along similar pathways that permitted the serpentinite intrusions that host most of these deposits. A recent paper posits a large mantle source of water from the former forearc during both the Mesozoic and Paleogene subduction era and after the transition to transpressive continental-transform kinematics of the San Andreas Fault System (Kirby, Wang, and Brocher, EPS 2014). We discuss this model in the context of the literature on the geology of California and its mercury ore deposits, and historical records of mercury mining in the State. We conclude that fluids derived from this source give insights into mobilization of serpentinite intrusions from the forearc mantle and established pathways for the ascent of carbonated hydrothermal fluids that created the silica-carbonate rocks and mercury ore deposits.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMDI44A..04K
- Keywords:
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- 1031 Subduction zone processes;
- GEOCHEMISTRYDE: 3613 Subduction zone processes;
- MINERALOGY AND PETROLOGYDE: 7240 Subduction zones;
- SEISMOLOGYDE: 8170 Subduction zone processes;
- TECTONOPHYSICS