Day 2, Stop 11
Iron Mineralization along Fault
GPS Location:
38o 19.434' N
111o 20.859' W
Ages:
Triassic
Rock Units:
Shinarump Member of the Chinle Formation
Moenkopi Formation
Features Present:
Iron oxide cementation along fault creates ~2 m wide resistant face (Fig. 1).
Interpretation:
Faults create conduits along which fluids can flow more easily. The concretionary mineralization results when iron bearing reducing fluids flow along the fault, come in contact with oxidizing fluids and iron oxide precipitates (e.g., Chan et al., 2000). Clusters of spheroidal concretions are also present (Fig. 3). The cementation causes a resistant ridge that runs parallel to the highway.
Figure 1: Resistant, iron oxide mineralization along face of fault (arrow).
Figure 2: Normal fault (shown with line) with Shinarump Member of the Triassic Chinle Formation (lower left) downthrown against the Triassic Moenkopi Formation (upper right). Large tick marks on scale bar = 1 cm.
Figure 3: Cluster of spheroidal iron oxide concretions. Large tick marks = 1 cm.