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Zircon Trace Element Variation From Mono Craters (California) Ashes And Domes As Recorders Of Temporal Changes In The Rhyolite Magma System, Natalie D. Baker
Zircon Trace Element Variation From Mono Craters (California) Ashes And Domes As Recorders Of Temporal Changes In The Rhyolite Magma System, Natalie D. Baker
Master's Theses
The Pleistocene to Holocene Mono Craters in eastern California comprise at least 28 high-silica rhyolite domes, lava flows and tephra cones. To examine the geochemical evolution of the magma system, trace elements were analyzed on crystal rims of zircons separated from juvenile pumice clasts from 5 ashes in the correlative Wilson Creek Formation (spanning from 62 to 21 ka) and from 3 rhyolite domes (21, 12.5, and 7 ka). Rare earth element (REE) patterns show similar overall shapes with prominent negative Eu anomalies, indicative of similar geochemical environments of zircon crystallization, but variation in key trace elements and ratios indicate …
Late-Stage Deformation And Exhumation Of A High-Pressure Metamorphic Belt In An Active Arc-Continent Collision, Taiwan, Michael Chojnacki
Late-Stage Deformation And Exhumation Of A High-Pressure Metamorphic Belt In An Active Arc-Continent Collision, Taiwan, Michael Chojnacki
Master's Theses
Structural analyses and fluid inclusion microthermometry were conducted within the blueschist facies, Yuli Belt in the Taiwan arc-continent collision in order to better understand the kinematics and pressure and temperature conditions associated with rapid exhumation (~10 km/myr) of high-pressure rocks. The most recent ductile deformation, observed as a penetrative fabric, S3, and relatively late, steeply dipping, mineral-filled, mode-I fractures, was characterized by vertical shortening, top-to-the southwest shear, and northeast-southwest extension. The late-stage veins record entrapment conditions ranging from 200°C to 450°C. To generalize, this structural and metamorphic history is interpreted to reflect the later stages of exhumation of the Yuli …
Fracture Analysis Of The Lower Oceanic Crust, Atlantis Bank, Southwest Indian Ridge, Trent Jackson
Fracture Analysis Of The Lower Oceanic Crust, Atlantis Bank, Southwest Indian Ridge, Trent Jackson
Master's Theses
Atlantis Bank (AB) is an oceanic core complex (OCC), formed at the slow-spreading (spreading rate/yr) Southwest Indian Ridge (SWIR)-Atlantis II transform junction. AB is a domal massif composed of lower crustal and upper mantle rocks exhumed along a normal-sense detachment shear zone/fault. OCCs are of high interest since oceanic crust comprises the majority of Earth’s crust and OCCs form up to 15% of the crust that is formed at slow-spreading ridges. Brittle deformation, such as faults and fractures provide pathways for fluids to interact with the crust, which increases heat and mass exchange between the crust and hydrosphere, and is …
Deformation, Sandstone Detrital Zircon Ages, And Provenance In And Near The Eocene Leavenworth Fault Zone, Washington, Francesca Isabella Senes
Deformation, Sandstone Detrital Zircon Ages, And Provenance In And Near The Eocene Leavenworth Fault Zone, Washington, Francesca Isabella Senes
Master's Theses
The North Cascades is an excellent area to study basins and strike-slip faults that formed during regional transtension. This structural, petrographic, and U-Pb geochronological study focuses on the Eocene Leavenworth fault (LVF), which separates Eocene non-marine clastic rocks of the Chumstick Formation and older Swauk Formation. The LVF has been interpreted as a dextral strike-slip fault active during Chumstick deposition and as a reverse fault. Poles to beds (n=207) in the Swauk Formation trend WNW, oblique to the ~320˚-striking LVF, and commonly dip SSW, defining a girdle and a fold axis plunging 4˚ toward 297˚. Beds (n=50) in the Chumstick …
Phreatomagmatic Eruption Deposits On The Seafloor Record Cataclysmic Caldera Formation On Axial Seamount, Juan De Fuca Mid-Ocean Ridge, Jacob Danielsen
Phreatomagmatic Eruption Deposits On The Seafloor Record Cataclysmic Caldera Formation On Axial Seamount, Juan De Fuca Mid-Ocean Ridge, Jacob Danielsen
Master's Theses
The physical and compositional characteristics of a unique ash-rich hydrothermal sediment, hydrothermal muddy tuff (HMT), on Axial Seamount, Juan de Fuca Ridge, suggest that it formed by phreatomagmatic eruptions during caldera formation. Deposit thickness trends away from the seamount summit and the presence of 68% primary volcaniclasts and 32% secondary lithics suggest a source from along caldera ring-faults deep in the crust. Lithic geothermometry indicates that the source was subject to low-temperature (<150 >°C) alteration, consistent with a provenance as deep as 600 – 800 m below the seafloor. At this depth, just above the critical point of seawater, the …