A Comparison of Pressure-Temperature-Time Histories Across the Burgess Branch Fault Zone, Northern Vermont

Gonzalez, Joseph P.; Baldwin, Suzanne L.; Kim, Jonathan J.; Webb, Laura E.

doi:10.1130/abs/2018ne-310874

Cited by 1 publication

(16 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Warren et al (2012) address the difficulty of using white mica ages from examined in thin section (Passchier and Trouw, 2005). If the rocks of the TPC reached ultrahigh-pressure conditions, as current research may imply Gonzalez et al, 2018), the observation of coesite is a possibility. Coesite, a high-pressure polymorph of quartz, is commonly preserved in ultrahigh-pressure metamorphic rocks as inclusions in minerals with radial fractures that form during a volumetric change related to the transition of coesite to quartz (Figure 1 -2;cf.…”

Section: Geochronologymentioning

confidence: 86%

“…The presence of eclogite and blueschist preserved in the TPC has implications for regional tectonic models, as refined models must include a mechanism by which high-pressure (≤ 2.5 GPa; Gonzalez et al, 2018) rocks were exhumed from depths as great as ~70 km . The preliminary interpretations, from prior research, for this exhumation include; exhumation via back-thrusting and normal faulting (Tremblay and Pinet, 2016, and references therein), the emplacement of a tectonic wedge into low-grade metamorphic rocks and resultant normal faulting (Lamon, 2001), as disconnected blocks in a serpentine channel (Thompson and Thompson, 2003), and exhumation in a buoyant, low-viscosity channel above the subducting slab .…”

Section: Exhumation Mechanismsmentioning

confidence: 99%

“…The final exhumation of high-grade metamorphic rocks (TPC) is inferred to be related to pre-Acadian normal faulting that removed overburden (Lamon, 2001). Tremblay and Pinet (2016) interpreted that the exhumation of ophiolites, as well as blueschist and eclogite of the TPC, was a result of transportation to the SE during Salinic back-thrusting, and subsequent Salinic normal faulting (such as the Burgess Branch Fault Zone; Gonzalez et al, 2018) that resulted in the removal of overburden and transportation to the surface.…”

Section: Tectonic Wedging and Back-thrustingmentioning

confidence: 99%

“…Early research interpreted the rocks of the TPC to have peak P-T conditions near the boundary of blueschist-eclogite-facies conditions during the Ordovician . More recently, research has estimated that peak conditions of blueschist and eclogite may have approached ultrahigh-pressure conditions Gonzalez et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Early research on the TPC yielded a single total fusion 40 Ar/ 39 Ar age from glaucophane (Laird et al, 1984). Recent studies (Pidgeon, 2017;Gonzalez et al, 2018;Tam et al, 2018) have produced additional total fusion and step-heated 40 Ar/ 39 Ar ages from white mica in the TPC and the area proximal to it. In this study, step-heated 40 Ar/ 39 Ar and in-situ U-Pb dating are used to analyze a variety of minerals from the metamorphic rocks of the TPC.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Geochronologic Constraints on the Timing of Metamorphism and Exhumation of the Tillotson Peak Complex in Northern Vermont

Aiken¹

2018

Geological Society of America Abstracts With Programs

Self Cite

View full text Add to dashboard Cite

microstructural observations to further constrain the subduction-exhumation history of the TPC. Microstructural and petrologic analyses in thin section on samples of felsic gneiss, pelitic schist, amphibolite, and blueschist suggest deformation during varied P-T conditions. The earliest and highest-pressure metamorphic event documented in the TPC samples is associated with inclusions in garnet and white mica in S1 quartz microlithons. Inclusions of paragonite, titanite, and omphacite in garnets, locally defining S1, suggest that some blueschist may have formed in the retrograde path in association with the S2 foliation. A greenschist-facies metamorphic overprint in most samples is also associated with S2, primarily defined by epidote, white mica, and chlorite. E-W trending F2 intrafolial folds are commonly rootless in outcrop, locally defined by blueschist-eclogitefacies fold noses. Kinematic indicators relative to S2 and L2 stretching lineations give a predominantly top-to-the-E shear sense. S3 crenulation cleavage development is related to folding about E-W trending F3 folds that define the map pattern of the Tillotson Peak Complex. Locally developed S4 crenulations are axial planar to the NW-trending Gilmore Antiform. Additionally, D4 deformation and metamorphism is recorded by microfractures in garnet and epidote, as well as chlorite pseudomorphs after garnet. 40 Ar/ 39 Ar step heating of multiple phases and U-Pb dating of titanite yielded ages corresponding with the Taconian to the Salinic orogenies. Ages of ~485-480 Ma are attributed to prograde-peak metamorphism (M1) and S1 development. Ages that span ~471-456 Ma are interpreted to document retrograde M2 metamorphism through greenschist to locally blueschist-facies metamorphic conditions during exhumation and S2 development. Correlation of D3 microstructures in these samples with map-scale folds suggest that E-W trending folds developed in the range of ~455-445 Ma, recorded by minimum apparent ages in the field area, and locally as plateau ages along the margin of the TPC. Younger ages ~435-405 Ma are observed locally in apparent age gradients, and are interpreted to reflect metamorphic overprinting that resulted in the chlorite pseudomorphs after garnet and the growth of actinolite, which may be related to the timing of folding about the Gilmore Antiform. Results presented here suggest the impact of Acadian retrograde metamorphism and deformation on rocks of the TPC may be less significant than previous work suggests. you enough for your patience when deadlines were approaching, as well as the advice you always had to offer. Additionally, I would like to thank my committee members, Don Ross and Keith Klepeis, for their feedback throughout this long process. Dan Jones without your knowledge and assistance in the lab, this research would have not been possible. I would like to thank Dr. Andrew Kylander-Clark for his willingness to examine titanite from our samples as a part of a pilot study. Jody Smith your availability and wisdom when it came to utilize th...

show abstract

Section: Geochronologymentioning

confidence: 86%

Section: Exhumation Mechanismsmentioning

confidence: 99%