Geological setting of listwanite (carbonated serpentinite) at Atlin, British Columbia: implications for CO2 sequestration and lode-gold mineralization

Abstract

Carbonate-altered serpentinite (listwanite) is commonly associated with gold mineralization, but also binds large quantities of the greenhouse gas carbon dioxide. At Atlin, listwanite alteration progressed through three carbonation reactions that resulted in the same overall mineral transformations as proposed for the industrial sequestration of anthropogenic CO2 by the process of mineral carbonation. Therefore, alteration of serpentinite to listwanite serves as a natural analogue to CO2 sequestration. Listwanite alteration is concentrated along faults and two orthogonal fracture sets, and extends tens of metres into the wall rock. One fracture orientation is preferentially mineralized. The carbonation reactions most distal to the fracture system consume olivine and brucite, and record grain-scale percolation of CO2-bearing fluids into serpentinite hundreds of metres from visible carbonate alteration. These previously unrecognized reactions may be relevant for in situ CO2 sequestration. Extensive carbonation in the carbonate alteration systems generated fracture permeability that promoted further infiltration and may have accelerated carbonation and gold mineralization.

A depositional model for hydromagnesite–magnesite playas near Atlin, British Columbia, Canada

“…Firstly, there is enrichment in 13 C of the well water relative to the spring water. The d 13 C and d 18 O values for the carbonate minerals in the magnesite, talc and quartz zones of the listwanite (carbonated serpentinite) in the Atlin region range from ca À7 to À1& VPDB and from ca 6 to 16& VSMOW, respectively (Hansen, 2005). A simple mixing model that takes into account the d 13 C values of the spring water and bedrock magnesite, and the increase in DIC concentration from the spring water to the well water results in d 13 C DIC values between À5& and À6&, which is reasonably close to the average d 13 C DIC of À6Á6& for the well water.…”

Deducing Mineralogy of Serpentinized and Carbonated Ultramafic Rocks Using Physical Properties With Implications for Carbon Sequestration and Subduction Zone Dynamics

“…Quantitative mineralogy for all whole‐rock powders was determined by qXRD at the Electron Microbeam and X‐ray Diffraction Facility, EOAS‐UBC; Atlin samples of Hansen (2005) were analyzed in 2004, whereas all other samples were analyzed in 2019–2020; for all instrumentation details and running conditions, see Table . Qualitative results for Atlin samples are reported in Hansen (2005) and quantitative estimates for the samples were then determined as part of this study. As qXRD estimates for minerals occurring in low abundance (∼1%) are relatively uncertain, brucite abundances from Atlin and Decar samples were further characterized by TGA.…”

“…We mostly relied on published major‐element chemistry data sets (Hansen, 2005; McGoldrick et al., 2017, 2018; Milidragovic & Grundy, 2019; Steinthorsdottir, 2021; Zagorevski, 2020). Samples from the Hogem area did not have corresponding published major‐element chemistry and these were sent to Geoscience Laboratories for lithogeochemical analysis using the XRF‐M01 and IRC‐100 packages (https://www.mndm.gov.on.ca/sites/default/files/2021%5Fgeo%5Flabs%5Fbrochure.pdf).…”

“…The 441 samples in this study were collected from the western Canadian Cordillera by various research groups (e.g., Hansen et al, 2004Hansen et al, , 2005McGoldrick et al, 2017McGoldrick et al, , 2018Milidragovic & Grundy, 2019;Milidragovic et al, 2018;Steinthorsdottir et al, 2020;Zagorevski et al, 2018 and references therein) from the traditional territories of the Taku River Klingit, Kaska Dena, Tāłtān Konelīne, Carcross/Tagish, Teslin Tlingit, Tl'azt'en, Binche Whut'en, Yekooche, and Takla First Nations. All localities comprise rocks that are part of the Atlin (equivalent to the undivided Cache Creek in southern B.C.)…”

Untitled

“…As this study provides new key insights into the formation process 20 of natural CO2-neutral magnesium-based cement on the field-and microscale, it could contribute in the 21 development of a new sustainable construction material. 22 23 24 CO2 sequestration (Cipolli et al 2004;Hansen et al 2005;Hänchen et al 2008;Kelemen & Matter 2008; 35 Wilson et al 2009;Beinlich et al 2010Hövelmann et al 2011;Oskierski et al 2013), and also the 36 reason for earlier research at the FUB (Beinlich & Austrheim 2012). This ultramafic complex is accordingly 37 weathered and displays an extensive fracture network with reaction rims despite its location in a subarctic 38 climate (Ulven et al 2017).…”