The Anatomy of an Antibacterial Clay Deposit: A New Economic Geology

Research Article| November 01, 2017 The Anatomy of an Antibacterial Clay Deposit: A New Economic Geology Keith D. Morrison; Keith D. Morrison School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404 ☼Present address: Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550; e-mail, morrison30@llnl.gov. Search for other works by this author on: GSW Google Scholar Stanley N. Williams; Stanley N. Williams School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404 Search for other works by this author on: GSW Google Scholar Lynda B. Williams Lynda B. Williams School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404 †Corresponding author: e-mail, lynda.williams@asu.edu Search for other works by this author on: GSW Google Scholar Economic Geology (2017) 112 (7): 1551–1570. https://doi.org/10.5382/econgeo.2017.4521 Article history received: 31 Dec 2016 accepted: 30 Jun 2017 first online: 28 Sep 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Keith D. Morrison, Stanley N. Williams, Lynda B. Williams; The Anatomy of an Antibacterial Clay Deposit: A New Economic Geology. Economic Geology 2017;; 112 (7): 1551–1570. doi: https://doi.org/10.5382/econgeo.2017.4521 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Abstract Argillic alteration zones associated with porphyry and epithermal deposits may contain clays that are antibacterial against antibiotic-resistant human pathogens, thus providing new economic potential for these deposits. This study examined the antibacterial activity of hydrothermal alteration zones in andesite porphyry and volcaniclastic rocks from a sulfur-and pyrite-rich clay deposit in the Oregon Cascades. The deposit is located along a fault zone west of Crater Lake, in Eocene-age volcanic rocks.Mineralogical relationships were used to deduce emplacement temperatures of the antibacterial clays, and oxygen isotopes of secondary quartz were used to deduce fluid sources. High-sulfidation alteration from magmatic fluids (200°–300°C) produced highly illitic Black clay with elemental sulfur and up to 19 wt % pyrite. Low-sulfidation, mixed magmatic-meteoric fluids (150°–200°C) produced pervasive Blue clay containing reduced Fe-bearing rectorite and minor pyrite (4–5 wt %). White clay containing smectite and kaolinite formed along faults from cooler (≤100°C) meteoric water. Surficial Red clay contains illite-smectite and goethite from the oxidation of pyrite.Antibacterial activity is greatest in the pyrite-bearing clays but the nonsulfide-bearing White clays also inhibit bacterial growth. Red oxidized clays are not antibacterial. When antibacterial clays are rehydrated in deionized water (100 mg/ml), the pH (<4.5) drives mineral dissolution and metal hydrolysis to produce Fe2+, Al3+, and hydroxyl radicals that kill bacteria. The pH and Eh of the hydrated clay is important for stabilizing these aqueous reactants, therefore we find no antibacterial effect where carbonates or goethite are stable. Accordingly, the antibacterial effect is diminished with burial depth (meters) where the Eh is too low to drive pyrite oxidation. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.