The worldclass Hemlo deposit is one of Canada's largest gold producers, containing 95 million tons of ore grading ~8 g/t Au; the mineralization is hosted mainly by two sub-parallel shear zones. However, unlike most Archean lode gold deposits, the ore occurs as finely disseminated Hg- and Ag-bearing native gold in potassically altered rocks, and is associated with molybdenite, stibnite and realgar. / Mineralization occurred at greenschist conditions (400 to 500°C), and was subsequently overprinted by a single metamorphic event that peaked at ~630°C and 5 to 7 kb, which recrystallized the ore and alteration assemblages. Retrograde cooling lasted for ~80 m.y., with temperature decreasing on average ~5°C per m.y. Ore formation involved three reactions that affected ∫S2,∫O2, and pH: the dissolution of sedimentary barite, the precipitation of pyrite, and the replacement of muscovite by K-feldspar. During sulfidation, caused by the dissolution of barite, iron partitioned preferentially into pyrite, which prevented the formation of Fe-bearing metamorphic index minerals (such as garnet and staurolite), oxides (e.g., magnetite, hematite, ilmenite), and low- ∫S2 sulfides (e.g., pyrrhotite). In addition, K-alteration strongly enriched the ore zones in K-feldspar (microcline) and muscovite, which buffered pH, and prevented formation of aluminosilicates. Hemlo is an example of a mesothermal deposit which formed from metamorphic fluids with a significant magmatic component. Deposition of native gold and molybdenite occurred due to decreases in pH and ∫O2 that accompanied potassic alteration and pyrite precipitation. Other elements, such as Sb and As were adsorbed initially onto pyrite growth surfaces. Near peak metamorphism, the deposit evolved a sulfide melt that formed through release of As and Sb from pyrite during metamorphic recrystallization, partial decomposition of primary minerals (such as native gold), and interaction of the melt with sulfur-bearing aqueous metamorphic fluids. The mineral assemblages that crystallized from this melt are similar to those predicted by experimental data for the As-Sb-S and related systems, and are interpreted to have formed by fractional crystallization.

The partly dolomitized Swan Hills Simonette oil field (Givetian-Frasnian) of west-central Alberta reached maximum burial (6500 m, Tpeak $=$ 160$ sp circ$C) during the Paleocene. Five buildup stages are recognized. The most consistently porous facies comprise grainy, proximal reef lithofacies. Early calcite spars occluded pores which influenced fluid flow during burial diagenesis. Dolomites have the highest porosities (up to 20%) due to leaching of calcite fossils. Permeability is greatest (up to 1000 mD) in porous dolomitized matrices. Fractures are typically plugged with pyrobitumen. Dolomite distribution is controlled by the more porous primary lithofacies and by proximity to faults. Most limestones are cemented tight although some contain up to 10% irreducible pores. Late-stage fluids that precipitated dolomites, calcites and sulphides ($ sp{87}$Sr/$ sp{86}$Sr $=$ 0.7370) probably were derived from the crystalline basement. These data can be explained by vertical flow of Laramide hydrothermal fluids along faults and lateral flow along the more porous and permeable facies.

The southwestern region of the Manicouagan reservoir occupies the structurally uppermost position in the Parautochthonous belt, in the Grenville province, in eastern Quebec. The region consists principally of well banded grey gneisses composed essentially of plagioclase, quartz and biotite. An assemblage of rocks consisting of dolomitic marbles, quartzites, iron formations and pelites, occurs throughout the region. This assemblage can be correlated to rocks in the tectonic foreland to the north of the Grenville Front, that were deposited on the continental margin of Laurentia during the Paleo-Proterozoic. / The east-striking, and moderately south-dipping, Utishku fault zone runs through the middle of the region, and juxtaposes eclogite-facies rocks to the north with amphibolite-facies rocks to the south. Kinematics on the Utishku fault zone are unclear. The relationship, however, of high-pressure rocks in the footwall, and lower-pressure rocks in the hangingwall, indicates a predominant normal fault motion. Mineral lineations on the Utishku fault zone plunge due south. Normal faulting was, therefore, oblique to the regional northwest-directed compression of the Grenville in eastern Quebec. / Mafic rocks from the Utishku fault zone preserve a prograde P-T path. In contrast, pelitic rocks from the Utishku fault zone preserve a retrograde P-T path. The mafic rocks were probably incorporated into the fault at a relatively late stage. It seems likely that the mafics were initially buried by a thrust fault, structurally below the Utishku fault zone, that was active synchronous to normal motion on the Utishku fault zone. The eclogite-facies rocks, to the north of the Utishku fault zone, may, therefore, be bounded by a thrust fault below and a normal fault above, that were coeval. / It is suggested that normal faulting and rapid exhumation of eclogite-facies rocks occurred synchronous to regional compression and relatively early in the history of the Grenville orogen.

Structures associated with dextral transpression on Finlay-Ingenika fault (FIF) in the McConnell Creek area, north-central British Columbia, are dominated by subvertical to vertical strike-slip faults, as indicated by a variety of kinematic indicators. Position-gradient tensors determined from strain analysis of deformed volcanic fragments in a succession of Late Triassic Takla Group rocks abutting one of the north-northwest trending faults indicate that they are dextrally transpressive, in accord with the common occurrence of subvertical intersections of the fault planes with other planar fabrics and subhorizontal stretching lineations within the fault zones. Principal directions of the magnetic susceptibility ellipsoids from Early Jurassic to Cretaceous dioritic rocks are consistent with those of the strain ellipsoids in their adjacent volcanics, suggesting that the plutonic rocks experienced the same deformation as the Late Triassic Takla Group volcanics. The age of the strike-slip faulting is unknown but was probably not earlier than mid Cretaceous as the Early Jurassic to Cretaceous dioritic rocks were involved in the faulting in many places. / Some of the major faults cut the area into discrete, fault-bounded blocks several kilometres wide. As the dextral motion on the FIF progressed, deformation was concentrated within the previously formed fault zones while the fault-bounded rocks remained weakly deformed. Stress tensors for 24 sites were inverted from the regional cleavage within the blocks, which predates the block-bounding faults. The site-mean stress tensors indicate that the fault-bounded blocks were rotated clockwise about a subvertical axis during progressive dextral motion on the FIF. The amount of rotation varies systematically over the area with maximum value (58.7 $ pm$ 3.3$ sp circ$) close to the FIF and minimum value (0.0 $ pm$ 1.6$ sp circ$) about 20 kilometres away from it. / Paleomagnetic samples were collected from 13 sites in the widespread Early Jurassic to Cretaceous plutonic rocks. Interpretable magnetic components of the Late Cretaceous, isolated by both stepwise AF and thermal demagnetization from 6 sites, were used to calculate the paleopole. The observed paleopole has a low value of Fisher's precision k = 48, and is significantly different from the Late Cretaceous reference pole for cratonal North America (CNA). After corrections for the local block rotations, the observed paleopole has a high value of k = 383 and moves closer to the reference pole but is still significantly different from it. Rotation about the Eulerian pole for the best-fitting small circle to the Tintina trench and northern Rocky Mountain trench fault zone, however, brings the observed pole into coincidence with that for CNA, and requires only $ sim$670 kilometres of dextral displacement on the fault zone. It is likely, therefore, that local structures associated with dextral strike-slip faults in the western Canadian Cordillera may account for at least part of the paleomagnetic disparity between some western parts of the Canadian Cordillera and CNA.

Deep basin Leduc Obed and Swan Hills Simonette calcite fluid inclusions yielded Th ranges of 127 to 172°C and 122 to 158°C; while saddle dolomites have Th from 136 to 148°C and 133 to 162°C, respectively. Calcite data from the subsurface suggest a 20°C/km geothermal gradient and saddle dolomite data a gradient around 23°C. Vug-filling calcites from Spray Lakes, Parker's Ridge and Big Hill, yielded Th data (128.0 to 155.1°C) similar to vug-filling cements from Obed and Simonette. Fluids in the fracture-filling saddle dolomites analysed have an average T h of 171.6°C and salinity of 17.1. Post-thrusting fractures yielded calcites with the lowest Th and salinity suggesting precipitation from cooler, largely meteoric waters. Homogenization temperature data for vug and fracture-filling from subsurface and outcrops suggest that late calcite and dolomite phases were precipitated near maximum burial, in the Paleocene. / Many of the Obed and Simonette late-stage calcites and dolomites have very high 87Sr/86Sr signatures (up to 0.7370). Obed late calcites show a strong east to west increasing trend in Sr isotopes across the buildup---suggesting fault control of this margin. (Abstract shortened by UMI.)

<p>Twelve electric borehole-image logs from oil wells located in the Long Beach oil field were used to conduct a fracture analysis of principal stress orientations associated with the Newport-Inglewood Fault Zone. The fractures analyzed are located in the Puente, Repetto, Pico, and San Pedro formations. Fractures were grouped based on fracture type, orientation, and formation. In-situ SHmax orientation was interpreted to range between 320? to 40?. Variations form the in-situ stress were observed across every formation and interpreted as paleo-stress. The SHmax orientation begins to change from NW to N-NW in the Pico Formation, which may signal the onset of the dextral movement of the Newport-Inglewood Fault 2.5 million years ago or later. The NE SHmax orientation in the San Pedro Formation may reflect stress trajectory changes as the Newport-Inglewood Fault continues to propagate in the Pleistocene. Additional SHmax orientations indicate a more complex structural evolution of stress trajectories.

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The Condit Dam breach on the White Salmon River (WSR) in Washington provided a unique opportunity to study how a bedrock-confined, gravel-bed river responds to a large influx of fine reservoir sediment. On October 26, 2011, a dynamite explosion breached a hole in the base of the 38 m tall dam, causing rapid reservoir erosion and downstream transport of fine sediment through the 5,300 m of channel separating the reservoir from the mouth of the WSR, where it flows into the Columbia River. In my research, I combined field data, aerial photographs, and LiDAR surveys to measure pre-breach and post-breach geomorphic conditions, up to 9 months after the breach, to assess downstream geomorphic response through a confined reach (reach 1) with forced pool-riffle morphology and a less-confined reach (reach 2) near the rivers mouth. I found that the magnitude and duration of geomorphic adjustment was smaller over riffles than pools and over reach 1 than reach 2. By 3 weeks after the dam breach, pools stored about twice as much of the reservoir-derived sediment (~95,000 cubic m) as riffles (~50,000 cubic m). By 9 months post-breach, nearly all (90%) of the sediment had been evacuated from riffles (~5,000 cubic m remained), whereas about half of the sediment initially stored in pools had been evacuated (~50,000 cubic m remained). Reach 1 stored ~145,000 cubic m within the 3 weeks after the dam breach compared to the 650,000 cubic m stored in reach 2. By 9 months post-breach, the volume of sediment stored in reach 1 (~40,000 cubic m) decreased by 72% and the volume in reach 2 (~490,000 cubic m) decreased by only 25%. I also found significant storage behind large wood deposits and throughout the transition between reach 1 and reach 2. My findings suggest a conceptual model by which reductions in grain and bedform roughness caused by initial sediment deposition in reach 1 contribute to sediment transport and deposition in reach 2. Findings from the WSR can help inform recovery from other sediment disturbances and dam removals.

<p> The Chattanooga Shale is a petroleum source rock within the Black Warrior Basin. Several attempts have been made to exploit this formation for unconventional shale gas. However, past studies of the Chattanooga indicate an area of the shale should produce liquid hydrocarbons. This paper expands upon the previous work by using old data to create a new model for the burial history and thermal maturation of the Chattanooga Shale. This new basin model incorporates formation lithologies, ages, thicknesses, and thermal maturity indicators. The long history of the Black Warrior Basin includes a significant period of unroofing. Part of the model seeks to estimate the thickness of the missing section. The study also addresses complex maturation patterns observed in the basin by previous workers. The author concludes that an oil window exists in the Chattanooga Shale.</p>

<p> Magnetic susceptibility has been used as an effective tool for affordable, rapid, and highly sensitive measurements that provide information about the compositional changes of mineral materials in rocks and soils. It has been demonstrated that a relationship between heavy metal concentrations, pollution, and magnetic susceptibility exists. The objective of this study is to use magnetic susceptibility as a method for the detection of the anthropogenic impact on the environment within Baton Rouge, Louisiana. Based on preliminary results from a previous study, we investigated a 100 square mile area, covering a variety of environmental settings, including urban areas and industrialized parts of the inner city. At each site, 20 magnetic susceptibility readings were taken and discrete surface and subsurface samples were collected for subsequent laboratory analysis.</p><p> Contour maps and histograms of magnetic susceptibility values indicate a close correlation between environmental setting and the intensity of magnetic susceptibility. Magnetic susceptibly increases within urban and industrialized areas compared to rural areas within the area of investigation. Enhanced susceptibility was observed in the industrialized areas in all magnetic parameters, including susceptibility maps of field measurements, discrete samples, and isothermal remanent magnetization. The field susceptibility data display a stronger correlation compared to the discrete sample analysis because of the statistically significant amount of data collected at each site. There is no apparent correlation between magnetic susceptibility and lithology/soil type in this area. Acquisition curves of the isothermal remnant magnetization indicate the presence of both high- and low coercivity minerals, probably magnetite with a small amount of hematite or goethite as the carriers of magnetic remanence.</p>