Characterization of Navajo sandstone hydrous ferric oxide concretions

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Title Characterization of Navajo sandstone hydrous ferric oxide concretions
Publication Type thesis
School or College College of Mines & Earth Sciences
Department Geology & Geophysics
Author Potter, Sally Latham
Date 2009-12-03
Description In Utah's Grand Staircase Escalante National Monument (GSENM), abundant spheroidal hydrous ferric oxide (HFO) concretions (cemented mineral masses) of the Jurassic Navajo Sandstone are present both in situ and loose in topographic lows. The HFO cement phases are typically amorphous HFO, goethite and hematite. Concretions are a significant record of diagenetic history, iron cycling and precipitation/mobilization events. The physical characterization of the concretions provides data to infer the processes affecting precipitation geometries and timing of precipitation events throughout the diagenetic history of the sandstone reservoir. Physical properties of the concretions also provide data to propose a model for formation of spheroidal HFO concretions. Three precipitation geometries are present in GSENM: 1. spheroidal (aspect ratio ranges from 1.00 to 1.06) to discoidal (aspect ratio >1.06) macro concretions >5 mm diameter, 2. spheroidal to discoidal micro concretions <5 mm diameter, and 3. HFO-lined joints and related asymmetrical loopy mineralization and banded precipitation patterns (Liesegang bands). Three end members of Utah macro concretions (rind, layered and solid) and two end members of micro concretions (rind and solid) are distinguished by internal structure. Different precipitation geometries result from a combination of diffusive and advective mass transfer. Multiple generations of cement textures and minerals suggest a pervasive growth model similar to some carbonate concretions where HFO concretions are precipitated with a set radius from multiple nuclei throughout the concretion. Chemical and mineral phase gradients detected via QEMSCAN and visible to near infrared (Vnir) reflectance spectroscopy suggest that concretions form initially from an amorphous HFO gel that dehydrates with age to more stable phases (goethite, hematite). Some internal structures of concretions are a result of overprinting from late-stage precipitation events. The Utah concretions interest planetary scientists because similarities with spherules in Meridiani Planum suggest that Mars "blueberries" also form via diffusive reactant transfer during groundwater diagenesis and Mars hematite likely had precursor HFO phases. Multiple mineralization events have probably occurred on Mars although variability of Utah concretions represents a more complex history of diagenesis. Concretions preserve a record of diagenetic events. Reservoir evolution is better understood by determining how concretions grow and change over time.
Type Text
Publisher University of Utah
Subject Geology--Utah; Grand Staircase-Escalante National Monument
Dissertation Institution University of Utah
Dissertation Name MS
Language eng
Relation is Version of Digital reproduction of "Characterization of Navajo sandstone hydrous ferric oxide concretions" J. Willard Marriott Library Special Collections QE3.5 2009 .P68
Rights Management © Sally Latham Potter
Format application/pdf
Format Medium application/pdf
Format Extent 95,195 bytes
Identifier us-etd2,132195
Source Original: University of Utah J. Willard Marriott Library Special Collections
Conversion Specifications Original scanned on Epson GT-30000 as 400 dpi to pdf using ABBYY FineReader 9.0 Professional Edition.
ARK ark:/87278/s6571sgn
Setname ir_etd
ID 192370
Reference URL https://collections.lib.utah.edu/ark:/87278/s6571sgn
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