<p> The Dolphin deposit is an intrusion-related gold deposit (IRGD) located approximately 30 km north of Fairbanks, Alaska. The deposit is in--and adjacent to--a composite mid-Cretaceous pluton intruding amphibolite facies metamorphic rocks. NI43-101 compliant gold resource estimations for the deposit utilizing a 0.3 g/t cut-off, is 61.5 Million tonnes (Mt) at 0.69 g/t indicated (1.36 million oz = Moz) and 71.5 Mt at 0.69 g/t inferred (1.58 Moz). </p><p> Due to extensive hydrothermal alteration of the intrusion, identifying lithology in hand sample and thin section, as well as by standard compositional techniques (SiO₂ vs. Na₂O + K₂O), has proven problematic. By plotting wt% TiO₂ vs. P₂O₅ obtained from XRF analysis and four-acid digest ICP-MS data, two distinct population clusters appear. By comparison with least-altered intrusive rock analyses from the Fairbanks district, the igneous units can be identified as granite and tonalite. Because there is no gradational transition through an intermediate granodiorite unit, they were most likely derived from two separate magmatic bodies rather than <i>in-situ</i> fractionation from a single parent. Tonalite is concentrated along the northern and eastern margins of the stock with granite composing the rest of the body. Tonalite xenoliths in granite and granite dikes intruding tonalite prove that tonalite is the older unit. </p><p> Investigations of hydrothermal alteration (based on chemical analyses, X-ray diffraction, and thin section examination) show albitic and advanced argillic (kaolinite-quartz) alteration are the dominant styles with sericite common throughout. Advanced argillic is a low temperature (&lt;300&deg;C) low pH alteration style that has not been previously identified in intrusion related gold deposits (IRGDs) in interior Alaska. Albitic alteration resulted from higher temperature, more neutral pH fluids. </p><p> Gold investigations show that gold occurs as coarse-grained Au&deg;, aurostibite, and maldonite in quartz + sulfide veins; fine-grained Au&deg; in the oxide zone; and in many forms in disseminated sulfide. These forms include Au&deg; inclusions in pyrite and arsenopyrite, solid-solution Au within compositionally zoned arsenopyrite, and as Au&deg; nanoparticles in pyrite and arsenopyrite. Using UAF&rsquo;s JEOL JXA-8530F microprobe, I found that solid-solution gold occurs only in arsenopyrite with strong compositional zoning. These have low As cores; gold-bearing mantles with moderate % As; and high As rims. In contrast, compositionally homogenous arsenopyrite does not contain solid-solution gold. Pyrite is commonly arsenian and carries dissolved gold (if any) near detection limits. Gold mineralization has not been tied to any lithology or alteration style; however, gold does seem to correlate with abrupt changes in alteration, especially between sericite + albite and kaolinite + sericite alteration and gold-bearing, zoned arsenopyrites are associated with advanced argillic alteration.</p><p>

The 85-m Brushy Basin Member of the Morrison Formation in western Colorado comprises a 30-m lower division mostly made of red-brown mudstone and a 55-m upper division characterized by variegated smectitic mudstones. River-channel sandstones embedded in the floodplain mudstones tend to have cut down to resistant caliche paleosols. Also present are thin beds of lacustrine micritic limestone and altered silicic ashfalls. These strata were studied at three locations, from west to east: Trail Through Time (TT), Fruita Paleontological Resource Area (FP), and Echo Canyon (EC). Morrison strata developed in a back-bulge depozone of a foreland basin system, with the debris eroded from thrust slices to the west. The Morrison strata differ from many foreland basins because the Morrison-age forebulge deposits west of the preserved basin were eroded due to plateau uplift of eastern Nevada and western Utah. Petrographic modal analyses of 87 sandstones date a major pulse of the Nevadan Orogeny at the transition from the Salt Wash Member to the Brushy Basin Member in late Kimmeridgian time. Brushy Basin sandstones show significant increases upsection in plagioclase, total lithic fragments, and especially volcanic fragments. Abundant volcanic ash accumulated on the floodplains. The source areas for the Morrison Formation were the Ellko and Mogollon Highlands with feldspathic litharenite sands characterized by relatively high proportions of lithic and volcanic fragments and plagioclase. Floodplain red-brown mudstones are highly smectitic with abundant smectite altered from silicic volcanic ash, in both the lower and the upper divisions. Depositional facies and architectural element analysis show that the rivers were low gradient, mainly anastomosing, with perennial flow and seasonal peaks in discharge. Dinosaur bone accumulations are found in some floodplain ponds. Isolated bones are present in anastomosing sandstones at the Trail Through Time. At Fruita Paleontological Resource Area, major acummulations of bones were rapidly buried in the deep pools at three bends in a meandering river.

<p> Compositional analysis of reservoir rock is a vital aspect of oil exploration and production activities. In a broad sense, knowing the mineral composition of a reservoir can help with characterization and interpretation of depositional environments. On a smaller scale, identifying mineralogy helps calibrate well logs, identify formations, design drilling and completion programs, and screen for intervals with potential problem minerals, such as swelling clays. The petroleum industry utilizes two main methods to find compositional mineralogy, x-ray diffraction (XRD) and thin section analysis. Both methods are time consuming, expensive, and destructive. An alternative method for compositional analysis that includes quantitative mineralogy is a valuable prospect, especially if it had the potential to characterize the total organic content (TOC). </p><p> The remote sensing community has been using infrared spectroscopy to analyze mineralogy for years. Within the last ten years, the advancement of infrared spectrometers and processing programs have allowed infrared spectra to be taken and analyzed faster and easier than before. The objective of this study is to apply techniques used in remote sensing for quantitatively finding mineralogy to the petroleum industry. While developing a new methodology to compositionally analyze reservoir rock, a database of infrared spectra of relevant minerals has been compiled. This database was used to unmix spectra using a constrained linear least-squares algorithm that is used in the remote sensing community. A core has been scanned using a hand-held infrared spectrometer. Results of the best method show RMS error from mineral abundance to be under five percent.</p>

<p>The Sierra Blanca metamorphic core complex (SBMCC), located 90 miles west of Tucson, is part of the southern belt of metamorphic core complexes that stretches across southern Arizona. The SBMCC exposes Jurassic age sedimentary rocks that have been metamorphosed by intruding Late Cretaceous peraluminous granites and pegmatites. Evidence of this magmatic episode includes polysythetic twinning in plagioclase, albite exsolution of alkali feldspar resulting in myrmekitic texture, and garnet, mica and feldspar assemblages. The magmatic fabric is overprinted by a Tertiary (Miocene?) tectonic fabric, associated with the exhumation of the Sierra Blanca metamorphic core along a low-angle detachment fault, forming the SBMCC. The NW-SE elongated dome of metamorphic rocks forms the footwall of the detachment shear zone, and is separated from the hanging wall, composed of Paleozoic and Mesozoic metasedimentary rocks, by a low-angle detachment shear zone. Foliation is defined by gneissic layering and aligned muscovite, and is generally sub-horizontal, defining the dome. The NNW-SSE mineral stretching lineation is expressed by plagioclase and K-feldspar porphyroclasts, and various shear sense indicators consistent with a top-to the-NNW shear sense. Lineation trends in a NNW-SSE orientation; however, plunge changes across the domiform shape of the MCC. Much of the deformation is preserved in the blastomylonitic gneiss derived from the peraluminous granite, including epidote porphyroclasts, grain boundary migration in quartz, lozenged amphiboles, mica fish, and retrograde mineral alterations. Detailed petrologic observation and microstructural analysis indicate deformation temperatures of 450-575 ? ?C presented here provide thermomechanical constraints on the evolution of the SBMCC.

Diagenesis is the sum of those processes whereby an originally sedimentary assemblage attempts to reach and maintain an equilibrium with its environment. Numerous factors influence and affect the diagenesis of sedimentary elastic assemblages - fundamentally unstable when deposited but never reaching equilibrium ith their environment. The interrelationship of these factors, however, precludes the identification of any single factor as wholly controlling the diagenesis of elastic sediments. The multifactorial nature of diagenesis is illustrated here by reference to the Middle Jurassic Dogger Formation and Ravenscar Group which outcrop on the North Yorkshire Moors and the Brent Group from Wells 3/3-1, -2, and -3 in the Ninian Field, and 210/15-2, also in the Northern North Sea.The Ravenscar Group is interpreted as being deposited in a fluvio-deltaic complex. Here, attempted equilibration of non-marine sediments with their pore waters resulted in a variety of diagenetic modifications. These are interpreted as being influenced strongly by bacterial degradation of organic matter, which lowered pH and then reduced Eh. This reduction of pH caused feldspar dissolution and muscovite neomorphosis to kandites throughout. Similarly, in the texturally and inineralogically mature sandbodies, quartz overgrowths and veriniform kandites precipitated from oxygenated pore waters, whilst chlorite and overgrowths formed in anoxic pore waters. This resulted in complete reduction of porosity in, and cementation of, finer and texturally less mature overbank sands. Conversely, channel sands were cemented into rigid but porous quartzose frameworks. In addition, soil horizons of sphaerosiderite developed as standing water on the floodplains stagnated. Bacterial ferric iron reduction throughout the water table then raised the pH and extensive siderite cements were precipitated. During burial, calcium carbonate saturated formation waters migrated into the remaining porous sandbodies and precipitated replacive ferroan calcite. In marine elastics, meanwhile, illite and potassium-feldspar overgrowths precipitated before in situ bacterial processes lowered pH here also. This resulted in dissolution of feldspars, muscovite neomorphism and precipitation of vermiform kandites. Subsequently, pH rose and ferroan calcite cementation occurred.It is suggested that "aggressive fluids" migrated into the larger connected sandbodies during burial. They dissolved the carbonate cements and precipitated dense pockets of blocky kandites. These sediments were little affected during continued burial. However, their Recent weathering may have dissolved carbonates and feldspars as well as neomorphosing chlorite to vermiculite.The reservoir rocks of the Ninian Field have formed from mature quartz-rich elastic sediments which accumulated in a transgressive sequence above Liassic mudrocks which was subsequently incised into by a fluvial system. Diagenetic modifications of the original sediments are similar to those of the Ravenscar Group, although neither chlorite nor soil horizons were observed in the wholly non-marine sediments. Porosity in marine sediments is occluded by extensive authigenic illite within a generally quartz framework. The effects of the fresh water table are also seen in the marine sediments over which the delta prograded. Then, during burial, ferroan calcite cementation and subsequent leaching and blocky kandite precipitation occurred here also. Hydrocarbon maturation and migration into the reservoir was preceded by alteration of pre-existing carbonates to ankerite, and. minor illitisation of blocky kandites. However, the only effort which can be related to oil emplacement is the widespread pyritisation around the oil-water contact.The sandstones from 210/15-2 are interpreted as formed from coarse elastic sediments which accumulated in a shallow-marine nearshore environment, possibly incised into by distributary channels. Initial marine connate water precipitated potassium-feldspar overgrowths before bacterial processes lowered pH and caused widespread kandite formation. Subsequently, these sediments were affected by ferroan calcite cementation, then leaching and blocky kandite precipitation. Although oil has migrated into these sediments, no other effects were observed.In addition to the factors which have been proposed previously as influencing diagenesis, I should like to propose that the climate of both the source area and of the depositional basin was of fundamental importance to diagenesis and many of the features observed in these rocks may be related to the original tropical climate. Moreover, as a result of the fundamental stability of the quartzose frameworks established during eogenesis, this climatic "finger print" may be recognised in all these sediments despite their subsequent diverse history.

<p> <b>Petrophysical evaluation of lithology and mineral distribution with an emphasis on feldspars and clays, middle and upper Williams Fork Formations, Piceance Basin, Colorado.</b> Understanding accessory mineralogy occurrence and distribution is critical to evaluating the reservoir quality and economic success of tight&ndash;gas reservoirs, since the occurrence of iron&ndash;rich chlorites can decrease resistivity measurements and the occurrence of potassium feldspar increases gamma&ndash;ray measurements, resulting in inaccurate water saturation and net&ndash;to&ndash;gross calculations, respectively. This study was undertaken to understand the occurrence and distribution of chlorite and potassium feldspar in the middle and upper Williams Fork Formations of the Piceance Basin at Grand Valley Field. </p><p> Eight lithofacies are identified in core based on grain&ndash;size, internal geometry, and sedimentary structures. Four architectural elements (channel fill, crevasse splay, floodplain, and coal) were determined from lithofacies relationships, and then associated with well&ndash;log responses. Logs and models were used to determine the occurrence and distribution of lithology, architectural elements, chlorite and potassium feldspar, as well as the relationships between minerals and lithology and architectural elements. Net&ndash;to&ndash;gross ratios vary stratigraphically, from 8% to 88%, with a higher average in the middle Williams Fork Formation (58.3%) than in the upper Williams Fork Formation (48.5%). Volumetric proportions vary stratigraphically for both channel fills (18&ndash; 75%) and crevasse splays (1&ndash;7%). </p><p> The average volume percent of chlorite and potassium feldspars are both &lt;1%, with P ₅₀ values of 1.3% and 7%, respectively. Chlorite is pervasive at the base of the middle Williams Fork Formation: almost 90% of the sandstones in sand&ndash;rich intervals contain chlorite. The distribution of chlorite did not vary between reservoir architectural elements, with 70% of both crevasse splays and channel fills containing chlorite. The results of this study show that, for the middle and upper Williams Fork Formations at Grand Valley Field, 1) there are eight lithofacies and four architectural&ndash;element types identified from core; 2) the occurrence and distribution of accessory minerals (&lt;10%) of chlorite and potassium feldspar can be accurately estimated from limited core and well&ndash;log data; 3) chlorite occurrence does not vary significantly between reservoir architectural elements; 4) the abundance of chlorite near completion intervals and the occurrence of potassium feldspar in calculated mudstone lithologies indicate a need to re&ndash;evaluate the utilization of saturation models and lithology calculations in reservoir&ndash;quality evaluations.</p>

The Scarborough Formation is the youngest marine horizon of formation status within the dominantly deltaic Aalenian - Bajocian Ravenscar Group, Cleveland Basin, northeast England. Sedimentary facies analysis has been performed on the three conformable lithostratigraphic units which make up the bulk of the Scarborough Formation outcrop: Blea Wyke, Byland Limestone and Crinoid Grit Members. This form of analysis was performed in an effort to determine the depositional environments of the members. The information derived from the study enables one to trace the palaeogeographic evolution of the Cleveland Basin throughout much of Scarborough Formation times.The clastic Blea Wyke Member [6 facies] is attributed to deposition in a shallow [&lt;4m], essentially microtidal,delta-destructive marine embayment. This embayment formed through non-eustatic marine transgression initiated by the compactional subsidence of an abandoned [Gristhorpe Member] delta lobe. Open to the east, the embayment covered some 2000km2 of the Cleveland Basin when fully established. A range of sand bodies evolved on the silty embayment floor in response to spatial and temporal changes in the wind-forced wave and current regime. These sand bodies included subtidal shoals, laterally extensive storm-emplaced sand blankets, and a classic delta-destructive sheet sand formed through the landward translation of a low-profile barrier bar.Under sustained rate-of-subsidence controlled marine transgression, clastic input to the Blea Wyke Member embayment eventually waned. In response, the overlying Byland Limestone Member [6 facies] was deposited in the western part of the Cleveland Basin in the form of a carbonate-dominated lagoon-barrier-inner shelf complex. The barrier component of the complex evolved through transgressive upward-shoaling under the influence of wind-forced wave and current activity. Composed of pellet lime grainstones, it protected a lagoon within which the dominant deposits were pellet lime mudstones, wackestones and packstones. Lithological and faunal similarities between the lagoon and inner shelf suggest that much of the shelf region may have comprised former back-barrier lagoon-fills exhumed during transgression.Byland Limestone Member times were terminated by an acceleration in the rate of marine transgression followed by tectonic uplift and subsequent geomorphic decay of the major landmass to the north [Mid North Sea High]. Transgression generated an east-west orientated epeiric seaway connecting the Sole Pit Trough with an areally restricted Pennine Massif. Within this seaway, clastic sediment derived chiefly from the Mid North Sea High was deposited in the form of a progradational, regional-scale composite sheet sand body: the Crinoid Grit Member [8 facies]. Deposition occurred under the combined influence of tidal currents, wind-forced currents and wave activity. Three main facies belts are recognised: paralic tidal sandwave complex, storm-dominated inner shelf and sandy middle shelf. The presence of a tidal sandwave complex is particularly interesting; it indicates that the forging of a marine connection to the west of the Cleveland Basin was necessary before tidal cyclicity could become prominent within the basin.

This thesis is an attempt to combine a number of different approaches as part of a wider attempt to re-interpret the late Quaternary history of the Vale of Pickering and Northern Wolds in Yorkshire. This involved the critical analysis of part evidence together with the collation and interpretation of data from a variety of sources, some published, some unpublished but mostly from field work.The course of the research followed a number of different lines. The first of these was to study the sedimentary data from glacial and pro-glacial deposits in the Vale of Pickering to assess their age and environment of deposition. The sediments were mapped in the field and analysed in the laboratory. A glacial outwash rather than lake-beach origin was proved for an important group of these sediments. The sedimentary data from the Vale of Pickering showed that ice had undoubtedly advanced further into the area than had been envisaged by Kendall at the turn of the century. - this was supported independently by geomorphological evidence and more sedimentary data from the northern Yorkshire Wolds escarpment. In the western end of the Vale, a thicker lobe of ice than that supposed by Kendall seems to have advanced into the area from the Vale of York, but its furthest limits cannot be shown from data available at the moment.On the Yorkshire Wolds an attempt was made to delineate the advance of the Late Quaternary ice, but unfortunately the data was so poor that no firm limits could be drawn. Glacial outwash sediments were found at several scattered sites and compared with those found in the Vale, some similarity was proved, suggesting that meltwater from late Quaternary glaciers had flowed across the Wolds and that ice from the Vale had overtopped the Wolds scarp along much of its length. The soils were analysed and found to have a higher blown sand content than suspected previously. The blown sand content increased towards the northwest, suggesting a probable glacial outwash source.The dry valleys were studied and new light shed on the processes which may have contributed to their formation. In addition evidence of periglacial evidence from the whole region was collected, described and assessed. Finally it was found that the structural lines of disturbance which traverse the chalk of the northern Wolds could easily be mapped from aerial photographs. These were mapped and included in the thesis as a small contribution to the solid geology of the area, even though they only impinge indirectly upon the main scope of this study.

The Penrith Sandstone and brockrams (breccio-conglomerates) are continental red-beds of Lower Permian and Permo-Triassic ages respectively. The brockrams are predominantly the deposits of coalescing alluvial fans which accumulated as the products of subaerial sheetflood, transitional debris flow and braided river processes at the margins of desert basins bordering the upstanding Lake District. The fans were deposited on an irregular topography which is demonstrated to have a probable minimum preburial relief of 250 to 300 metres in west Cumbria. The cross-stratified Penrith Sandstone of the Eden Valley accumulated as the foresets of large scale (up to 100 metres width) aeolian dunes orientated in response to a uniform east-south-easterly palaeowind. Dune-bedding within these deposits indicates a crescentic-downwind (barchanoid) configuration for the dune slipfaces. The stratigraphic unit termed the 'Upper Brockram' is believed to represent the deposits of ephemeral streams (arroyos) which flowed through and reworked part of the aeolian sand sea of the Penrith Sandstone. Nodular carbonate profiles occurring within sandstone/siltstone horizons intercalated with distal alluvial fan deposits in west Cumbria are interpreted as immature caliche soil horizons and represent periods of surface stability (non-deposition) of indeterminate length. Petrographic evidence indicates the most important process of formation to have been that of replacement of the detrital quartz component by microcrystalline non-ferroan calcite. Extensive post-depositional (diagenetic) modification to the mineralogy and texture of the brockrams of west Cumbria has resulted from the mechanical infiltration of clay, the dissolution of the less stable detrital components (primarily volcanic clasts), replacement by secondary clay and the precipitation of interstitial and void-filling authigenic clay, a hydrated haematite precursor mineral, ferroan and non-ferroan calcite and gypsum. Most reactions are considered to have occurred as stages within an evolving diagenetic sequence.

This study is based on palynological investigations at three sites in Java: Bandung Lake, Trinil and Bumiayu. At Bandung Lake (Holocene) three cores were studied, while surface section samples were studied from Trinil in East Java (Middle Pleistocene) and Bumiayu in Central Java (Upper Pliocene). The Trinil site is well known for its hominid fossils.The pollen flora at each site is fully described and illustrated while the pollen record at each location is used to reconstruct their vegetational, environmental and climatic histories. An attempt has also been made to determine whether palynology can be used to assist in dating these deposits. At all three sites, the character of the local vegetation is better reflected than that of the regional vegetation.One of the Bandung sites (Rancaekek) was radiocarbon dated, suggesting deposition between 11,000 and 7,000 yr BP and represents a freshwater lake deposits. The lake gradually shallowed toward 7,000 yr BP, at which time it was drained. The regional pollen component suggests climatic amelioration at about 8,000 yr BP, possibly reflecting the maximum incoming of solar radiation experienced in the Northern Hemisphere about 9,000 yr BP.Studies at Trinil revealed a mosaic of forest and open vegetation growing on a lahar. The former climate at this locality was probably markedly seasonal, not unlike that of the present day. Palynology conclusively demonstrates that this sequence is Pleistocene rather than Pliocene in age. The palynological record at Bumiayu reflects a regressive sequence with lagoonal and freshwater lacustrine environments (Kalibiuk Formation) followed by freshwater fluvial deposition (Kaliglagah Formation). The climate during the deposition of this sequence was markedly seasonal. The data support an Upper Pliocene age for the Bumiayu sequence.Three taxa are shown to have become extinct in Java during the Plio-Pleistocene. These are Stenochlaena lamrifolia and S. areolaris, which become extinct at the end of the Pliocene, and Daczydium, which is thought to have become extinct during the Holocene.