Timing of the Cenozoic “Great Hydration” event beneath the Colorado Plateau: Th-Pb dating of monazite in Navajo volcanic field metamorphic eclogite xenoliths

Geology ◽  
2015 ◽  
Vol 43 (8) ◽  
pp. 727-730 ◽  
Author(s):  
Daniel J. Schulze ◽  
Donald W. Davis ◽  
Herwart Helmstaedt ◽  
Brian Joy
Keyword(s):  
Colorado Plateau ◽  
Volcanic Field ◽  
Navajo Volcanic Field

Massive Fluid Influx beneath the Colorado Plateau (USA) Related to Slab Removal and Diatreme Emplacement: Evidence from Oxygen Isotope Zoning in Eclogite Xenoliths

2020 ◽  
Author(s):  
William F Hoover ◽  
F Zeb Page ◽  
Daniel J Schulze ◽  
Kouki Kitajima ◽  
John W Valley
Keyword(s):  
Oxygen Isotope ◽  
Secondary Ion Mass Spectrometry ◽  
Colorado Plateau ◽  
Volcanic Field ◽  
Oxygen Isotope Ratios ◽  
Core Composition ◽  
Plateau Uplift ◽  
Flat Slab Subduction ◽  
Dehydration Processes ◽  
Navajo Volcanic Field

Abstract The Colorado Plateau has undergone as much as 1·8 km of uplift over the past 80 Myr, but never underwent the pervasive deformation common in the neighboring tectonic provinces of the western USA. To understand the source, timing and distribution of mantle hydration, and its role in plateau uplift, garnets from four eclogite xenoliths of the Moses Rock diatreme (Navajo Volcanic Field, Utah, USA) were analyzed in situ for δ18O by secondary ion mass spectrometry. These garnets have the largest reported intra-crystalline oxygen isotope zoning to date in mantle-derived xenoliths with core-to-rim variations of as much as 3 ‰. All samples have core δ18O values greater than that of the pristine mantle (∼5·3 ‰, mantle garnet as derived from mantle zircon in earlier work) consistent with an altered upper oceanic crust protolith. Oxygen isotope ratios decrease from core to rim, recording interaction with a low-δ18O fluid at high temperature, probably derived from serpentinite in the foundering Farallon slab. All zoned samples converge at a δ18O value of ∼6 ‰, regardless of core composition, suggesting that fluid infiltration was widely distributed. Constraints on the timing of this fluid influx, relative to diatreme emplacement, can be gained from diffusion modeling of major element zoning in garnet. Modeling using best estimates of peak metamorphic conditions (620 °C, 3·7 GPa) yields durations of <200 kyr, suggesting that fluid influx and diatreme emplacement were temporally linked. These eclogite xenoliths from the Colorado Plateau record extensive fluid influx, pointing to complex hydration–dehydration processes related to flat-slab subduction and foundering of the Farallon plate. Extensive hydration of the lithospheric mantle during this fluid influx may have contributed to buoyancy-driven uplift of the Colorado Plateau and melt-free emplacement of Navajo Volcanic Field diatremes.

scholarly journals A Geophysical Model for the Origin of Volcano Vent Clusters in a Colorado Plateau Volcanic Field

2017 ◽  
Vol 122 (11) ◽  
pp. 8910-8924 ◽  
Author(s):  
Fanghui Deng ◽  
Charles B. Connor ◽  
Rocco Malservisi ◽  
Laura J. Connor ◽  
Jeremy T. White ◽  
...  
Keyword(s):  
Colorado Plateau ◽  
Volcanic Field ◽  
Geophysical Model
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