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Goals (and conclusions)
1. Summarize the evolution of the Laurentian craton: segmented and heterogeneous nature of the lithosphere the need for 4-D integrated studies within EarthScope. 2. Summarize results from the CD-ROM experiment: pose alternative hypotheses for reddite and blueite the need for 3-D deployments of the flexible array. 3. Summarize the Southwestern U.S. EarthScope “superexperiment” proposal: a new paradigm for integrated and inclusive regional experiments within EarthScope. 4. Muse about the best targets for a Northern Rockies “Superexperiment”: towards a single integrated EarthScope experiment in the northern Rocky Mountains.
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History and structure of the Wyoming Archean province–
oldest parts of North American lithosphere secular change in lithospheric processes?
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Extent of ~ 2.0 Ga Paleoproterozoic juvenile crust?
Nature of Paleoproterozoic rifting in creating long-lived lithospheric boundaries
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Great Falls Tectonic Zone and Vulcan Structure as parts of the greater Trans-Hudson:~ Ga continent- continent collisions; “birth” of Laurentia
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Extent of Trans-Hudson age tectonism beneath
Proterozoic accreted terranes
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Yavapai and Mojave provinces: interaction of collisional
and accretionary orogens ~ Ga
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Figure 3
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Quartzite-rhyolite successions occur late in Yavapai orogeny
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includes the Labradorian province
Mazatzal province: ~1.65 Ga juvenile crust, includes the Labradorian province
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stitch pre-1.65 Ga accreted crust
~1.65 Ga Mazatzal plutons stitch pre-1.65 Ga accreted crust
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1.45-1.35 Ga Belt Basin related to accretion in south??
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Grenville orogenic cycle,
Assembly of Rodinia: juvenile crust accreted during the Grenville orogenic cycle,
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Grenville-aged extension & widespread normal faulting
1.1 Ga Midcontinent and related rifts: mafic dike swarms, Grenville-aged extension & widespread normal faulting
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Western margin of Laurentia
formed via Ma breakup of Rodinia, Gunbarrel Dikes & Windermere Supergroup
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Long-lived accretionary
plate margin in southern Laurentia: Ma
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The nature and origin of mantle heterogeneity– a problem
best solved in the Rockies CD-ROM RISTRA
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Figure 3
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Body Wave Tomography: RISTRA Small-scale convection?
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Comparing CD-ROM and RISTRA:
anomalies align along Precambrian structures? The need for 3-D
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EarthScope Southwestern U.S. Superexperiment: Diverse tectonic elements in the Southwest require a 3-D seismic experiment integrated with geology
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EarthScope Southwestern U.S.
Superexperiment: Densification of Bigfoot (blue grid) to achieve 3-D resolution of regional tectonic provinces and 10-km-scale mantle velocity contrasts, and 4-D understanding of lithospheric evolution
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MT images need to be integrated with seismic, geodetic, and geologic datasets
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What is the extent to which
topography is influenced by crustal versus mantle density variations and when and how did the density structure develop?
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The nature and origin of mantle heterogeneity– a problem
best solved in the Rockies CD-ROM RISTRA
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Mantle to groundwater interconnections via analysis of deeply sourced
CO2 springs containing mantle-derived helium
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Conclusions The crust and upper mantle are segmented and highly heterogeneous and cannot be well understood without a 4-D integrated approach within EarthScope. There are two models to explain large velocity transitions (redite and blueite): 1) small scale asthenospheric convection, versus 2) preservation of old compositional provinces: We need 3-D deployments of the flexible array to resolve the relative importance of each model.
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Goals and Conclusions 3. EarthScope needs to forge a new paradigm for large integated, collaborative, and inclusive regional experiments. 4. A Northern Rockies “Superexperiment”: could propose a single integrated experiment that addresses an integrated set of uniquely well-posed problems in the northern Rocky Mountains: Yellowstone, Archean Wyoming province, west edge of Laurentia, and neotectonics of the northern Rockies.
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