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The complex, 300-m.y. evolution of the Paradox Basin featured numerous paleofluids of diverse types. Their flow through rocks, and interactions with each other and with the rocks, created zones of alteration and mineralization that are still visible today. Studying these provides valuable insights into the processes of paleofluid flow and rock alteration, not only in the Paradox Basin, but in basinal systems worldwide. This article presents some preliminary geological and mineralogical descriptions of altered (± mineralized) areas that we will visit on the field trip and discusses their implications for the nature, timing, and effects of paleofluid flow in the Paradox Basin. This work is part of an ongoing study of paleofluids in the Paradox Basin, so all results presented here are preliminary and are necessarily incomplete. For geologic and geochemical background, the reader is referred to the introductions by Jon Thorson (2018) and Mark Barton et al. (2018). Figure 1 provides a schematic overview of the stratigraphy and the stratigraphic distribution of some of the alteration and mineralization features we will see on the field trip. 

This field trip focuses on several of the classic Cu and U(-V) ore systems of the Colorado Plateau in the context of diverse geologic environments, processes, and consequences of fluid flow of the Paradox Basin. The Paradox Basin contains a >300-m.y. history of fluid flow and resource generation. Late Paleozoic development of a K-rich evaporitic foreland basin created a setting upon which later fluid-dominated processes generated economically significant accumulations of hydrocarbons, K-rich brines, CO2, and—most notably—metals including, significant deposits of Cu and some of the largest U and V resources of the United States. The sourcing and movement of fluids of diverse types and the resulting multiplicity of metasomatic features reflect a complex history starting with salt movement beginning in the Permian, sedimentation continuing intermittently into the Paleogene, distal manifestations of Cretaceous to Paleocene orogenesis, Cenozoic magmatism and, most recently, Neogene exhumation. In light of this broader context, we will examine Cu(-Ag) systems associated with salt anticlines at Paradox Valley (Cashin mine) and Lisbon Valley (Lisbon Valley mine), superimposed modern and ancient systems at Sinbad Valley, and contrasting U-V systems in the Jurassic Morrison Formation at Monogram Mesa (Uravan district) and Triassic Chinle Formation at Lisbon Valley (Big Indian district). In these areas, we consider the types and sources of various fluids (brines, hydrocarbons, meteoric), their solutes, the sequence of events, and links to overall basin evolution. A key objective of the trip is to use these examples and current interpretations to stimulate discussion and research about fluid flow and mass transfer in basinal settings.