Located at an important intersect between orogenic Au deposits in Sweden’s Gold Line and volcanicmassive sulphide (VMS) deposits in the Skellefte Mining District, the Barsele area is of high interest.Currently, the Barsele deposit consists of the Norra VMS deposit and 3 intrusive-hosted orogenic Audeposits: Avan, Central, and Skiråsen which are hosted in a 1876 ± 10 Ma early orogenic granodiorite(Thomas, et al., 2019). The aim of this thesis is to create a structural and geological model of the Barsele area whilst improvingthe understanding of the structural controls on VMS and intrusive-hosted Au mineralisation in thearea. Furthermore, this thesis aims to highlight prospective areas for future study and targeting inhopes to aid mineral exploration in the region. Geological mapping has been carried out in an area ofaround 440km2, with emphasis on structural measurements. 381 outcrop observations and more than4200 structural features were recorded using a combination of traditional and digital mappingmethods, including the use of Field Move by Petroleum Experts. The area was chosen as part of AgnicoEagle, Sweden’s mineral exploration project. The region has been affected by two dominant, syn-metamorphic cleavage forming events. The eventsdefine the main phase of the Svecofennian Orogeny which has produced ubiquitous slaty cleavage, Ndirected thrusts, and steeply inclined axial surfaces throughout the region. The region is characterisedby important N-S displacements with sinistral movement along major N-S trending transfer faults. Theabsence of strike-slip shearing in D1 structures indicates that D1 deformation was dominantly coaxialin nature and developed due to SW-NE crustal shortening. Along with this, a major ESE-WNW-strikingshear zone is identified with an inferred syn-extensional (D1) origin. D2 involved fault inversion and reactivation of syn-extensional faults as reverse shear zones. E-Wtrending lineations along more brittle SSW-NNE striking shear zones inferred to indicate an E-Worientation for crustal shortening during D2. D3 caused reactivation of the N-S-striking high-strain zones with reverse kinematics. This reactivationof trending shear zones resulted in strain partitioning into N-S zones. D3 is manifested by broad, open,N-NE trending upright folds of bedding and S2 foliation. 1st, 2nd, and 3rd order D3 structures have beencharacterised and illustrated by combining a range of data including outcrop observations, regionalStereonets, magnetic anomaly maps, and other geophysical maps.

The Snoqualmie pass area lies about 50 mi (80 km) east of Seattle, Washington, along the crest of the Cascade Range. Five stratified units, forming a composite section over 22,000 ft (6700 m) thick, are recognized in the area. They were deformed and later intruded by granodiorite and quartz monzonite porphyry of the Snoqualmie batholith (middle Miocene). The oldest unit, the Denny Formation (Permian), 7000 ft (2100 m) thick, consists of interstratified basalt, andesite and dacite volcanic rocks and limestone and chert beds. This formation is unconformably overlain by a thick conformable sequence of early Tertiary strata which are subdivided, from oldest to youngest, into the Guye Formation, Mount Catherine Tuff, and Naches Formations (Paleocene to early Oligocene). The Guye Formation, 6500 ft (1980 m) thick, consists of carbonaceous mudstone, quartzofeldspathic siltstone and sandstone, and chert conglomerate. The Mount Catherine Tuff, 900 ft (274 m) thick, consists of interstratified dacitic and rhyolitic crystal-vitric welded tuff. The Naches Formation, more than 6000 ft (1830 m) thick, is composed of carbonaceous mudstone and quartzofeldspathic siltstone and sandstone with interstratified andesitic lava and pyroclastic rock. The Denny Mountain Formation, informally named, 1800 ft (550 m) thick,(Oligocene or early Miocene) overlies the Guye Formation along a major angular unconformity. This unit consists of interstratified dacitic and andesitic tuff, volcanic breccia, and intercalated andesitic lava. The rocks of all stratified formations except the Denny Mountain Formation were deformed at different times before emplacement of the Snoqualmie batholith. During batholithic emplacement, four stages of deformation are recognized: (1) development of an anticline in the Guye, Mount Catherine Tuff, and Naches Formations, (2) break-up of this anticline and downfaulting of limbs with displacements up to 2 mi (3.2 km), (3) uplift of blocks of the Denny Formation and juxtaposition of these with younger formational units, and (4) uplift of additional blocks of the Denny Formation along trends that cut obliquely across stratigraphic contacts and previous structural trends. Intrusion of the Snoqualmie granodiorite and quartz monzonite porphyry into limestone beds of the Denny Formation has formed local deposits of skarn containing principally magnetite and lesser amounts of chalcopyrite.

The upper Nehalem River-Wolf Creek area is located on the northeastern flank of the Tillamook Highlands in the northern Oregon Coast Range. Three rock stratigraphic units underlie the thesis area, and these units range from late Eocene to Oligocene in age.

The Portland Hills fault forms a strong northwest trending lineament along the east side of the Tualatin Mountains. An en echelon lineament follows North Scappoose Creek, Alder Creek, and the Clatskanie River along the same trend, through Columbia County, Oregon. The possibility that this lineament follows a fault or fault zone was investigated in this study. Geophysical methods were used, with seismic refraction, magnetic and gravity lines run perpendicular to the lineament. The seismic refraction models indicate the near surface basalt is broken in many places, with 15 - 30 meters (50 - 100 feet) vertical displacement, down to the west, at Bunker Hill along the Alder Creek fault. Gravity models required a faulted zone approximately two kilometers wide across the lineament. The proposed fault zone is more clearly defined in the south, becoming more diffuse and branching in the northern part of the study area. The Bouguer gravity values from this study distort the -40 milligal contour farther to the northwest than is shown on the Complete Bouguer Gravity Anomaly Map of Oregon {Berg and Thiruvathukal, 1967b). The existence of sharp topographic features and the geophysical evidence indicate fault activity along the zone.

In the central Aegean of Greece, metamorphic rocks have been brought to the surface along multiple detachment faults producing a series of core complexes. The detachment faults have been grouped into several detachment systems including the North and West Cycladic Detachment Systems. The timing and magnitude of displacement along individual detachment faults is variable, the faults exhumed footwall rocks with a range of metamorphic grades from different crustal depths. Geochronology (zircon (U-Th)/He and white mica ⁴⁰Ar/³⁹Ar analyses) was conducted to investigate the timing of activity along a paired detachment system exposed in the bedrock of Mt. Hymittos, Attic Peninsula, Greece. Taken together the geochronometers indicate the detachments of Hymittos were active from the late Oligocene to the late Miocene with both faults active during the middle Miocene. The ductile-to-brittle deformation of the structures, top-SSW kinematics, morphology of the massif, and metamorphic grade indicate that these detachments are extensions of the West Cycladic Detachment System. Additionally, the overlap in timing between the structures indicates that paired detachment systems can be coeval. Coeval displacement along separate detachment branches has important implications for strain partitioning within the crust and the development of detachment systems. Detrital zircon U-Pb geochronology was conducted on samples from exposures of the West Cycladic Detachment System on the Attic Peninsula. The results are compared to unpublished data from the Attic Peninsula and the Western Cyclades including Santorini. The analyses confirm the correlation of the footwall rocks of Hymittos to the Cycladic Blueschist Unit as well as evaluate several paleogeographic correlations for the Cycladic Blueschist Unit. The samples herein record significant recycling of Variscan zircon from the Cycladic Basement, strongly suggesting the proto-Cycladic Blueschist Unit was deposited atop the Cycladic Basement. The Pindos Zone of the Hellenides is the most likely paleogeographic equivalent to the Cycladic Blueschist Unit. Strengthening this correlation gives additional insight into the position of the proto-Cycladic Blueschist Unit which is important for understanding both the movement of Hellenic terranes through time, and the pre-subduction relationship(s) between the terranes that today comprise the Attic-Cycladic Complex. Finally, electron backscatter diffraction analysis was utilized to examine the mechanisms of deformation in a suite of calcitic and dolomitic marble mylonites from the detachments of Hymittos. This was used to shed light on the conditions under which these ductile-then-brittle structures deformed suggesting that dolomite deformed under lower to sub-greenschist facies conditions may be surprisingly weak when deforming by grain size sensitive processes. Dolomite is a major rock forming mineral and comprises significant parts of carbonate dominated terranes and (meta)sedimentary successions. The apparent weakness of dolomite reported herein suggests that under greenschist and sub-greenschist facies conditions dolomite may accommodate significant strain not predicted by experiments or commonly reported from the field. Together this thesis provides insight into detachment fault architecture, deformation processes and the pre-subduction dynamics and structural position of the geologic units exposed within the Attic-Cycladic Complex.

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<p>Erosion, in its many forms, is thought to have a measurable impact on the development and evolution of mountain belts. In this work, we examine the response of physical scaled (analog) Coulomb wedges to different erosional styles. Data is collected in the form of velocimetry data within images of these models, using particle image velocimetry (PIV) and particle tracking velocimetry (PTV), with each dataset rendering whole wedge slip magnitude fields and material pathways, respectively. Results for channelized glacial erosion models demonstrate a significant focusing of faulting below the glacial channel itself, as well as a shift of the locus of greatest exhumation to within the channel. This shift in the locus of exhumation also allows for deep material to make it to the model surface, with models featuring a strong basal décollement having higher amounts of exhumation than those with weaker basal décollements. This same pattern is seen with regards to fault slip and shortening, with stronger décollement allowing for greater slip and more shortening. Increases in erosion magnitude are also seen as increasing total fault slip as well. With regards to thermal conditions and surface heat flow, we highlight that increasing erosion increases heat flow and temperatures within the wedge. Using Pressure-Temperature-time (P-T-t) pathways, we also see that the inclusion of weak material stratigraphy allows for duplexing and subsequent exhumation of deep-seated material, leading to complex thermal histories. Overall, we see erosion localization and magnitude being proportional to the magnitude of fault activity, and that this increased fault activity allows for deep-seated material to be exhumed from the system.  </p> <p>  </p>

Active seismicity and volcanism north of Washington state’s Mount St. Helens provide key ingredients for hydrothermal circulation at depth. This broad zone of seismicity defines the St. Helens Seismic Zone, which extends well north of the volcanic edifice below where several faults and associated fractures in outcrop record repeated slip, dilation, and alteration indicative of localized fluid flow. Candidate reservoir rocks for a geothermal system include marine metasediments overlain by extrusive volcanics. The colocation of elements comprising a geothermal system at this location is tested here by analysis of the structures potentially hosting a reservoir, their relationship to the modern stress state, and temperature logs to a depth of 250 m. Outcrop mapping and borehole image log analysis down to 244 m document highly fractured volcaniclastic deposits and basalt flows. Intervening ash layers truncate the vertical extent of most structures. However, large strike slip faults with well-developed fault cores and associated high fracture density cross ash layers; vein filling and alternation of the adjacent host rock in these faults suggest they act as vertically extensive flow paths. These faults and associated fractures record repeated slip, dilation, and healing by various dolomite, quartz, and hematite, as well as clay alteration, indicative of long-lived, localized fluid flow. In addition, where these rocks are altered by igneous intrusion, they host high fracture density that facilitated heat transfer evidenced by associated hydrothermal alteration. Breakouts in image logs indicate the azimuth of SHmax in the shear zone is broadly consistent with both the GPS plate convergence velocity field as well as seismically active strike slip faults and strike-slip faults mapped in outcrop and borehole image logs. However, the local orientation of SHmax varies by position relative to the edifice and in some cases with depth along the borehole making a simple regional average SHmax azimuth misleading. Boreholes within the seismic zone display a wider variety of fracture attitudes than those outside the shear zone, potentially promoting permeability. Temperature profiles in these wells all indicate isothermal conditions at average groundwater temperatures, consistent with rapidly flowing water localized within fractures. Together, these results indicate that the area north of Mount Saint Helens generates and maintains porosity and permeability suggesting that conditions necessary for a geothermal system are present, although as yet no modern heat source or hydrothermal circulation was detected at shallow depth. / Geology