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Iron+Ti±P±HFSE enriched rocks are found in a variety of localities worldwide, including some that are temporally and spatially related to Proterozoic AMCG (Anorthosite-Mangerite-Charnokite-Granite) suites. The origin of these enriched rocks has been widely debated and petrogenetic models such as liquid-liquid immiscibility, fractional crystallization and mineral accumulation, hydrothermal fluid enrichment, and residual liquids concentrated by filter pressing have all been proposed to explain occurrences of these rocks associated with AMCG suites. This locality is particularly distinct for two reasons, 1) abundant and large (>2.5mm) zircon, which contrasts with many Fe+Ti±P±HFSE enriched rocks where apatite is the main REE carrier 2) the mineralized zones are located as thin veins (up to 3 cm wide) located at the contact between two rock-types – an equigranular olivine-clinopyroxene-monzonite and a porphyritic orthopyroxene-clinopyroxene monzonite. Field relationships down to the microscale suggest the mineralization is related to the equigranular monzonite - the mineralized zones show planar contacts with the porphyritic monzonite, while it protrudes in between mesoperthitic feldspar grains of the equigranular monzonite. The mineralized zones likely developed from the equigranular monzonite, while the porphyritic monzonite served as a boundary where the mineralization was concentrated. Mg# and Fo% in clinopyroxene and olivine, respectively, are highest in phases of the mineralization (35.0 and 6.17) compared to the equigranular monzonite (22.2 and 2.50) and are can be suggested to be early-forming. Magnetite in the mineralization also has relatively elevated V and Al, which are known to behave as fractionation indices, and indicates earlier forming magnetite compared to magnetite in the equigranular monzonite. Strontium content and Eu/Eu* of apatite in the mineralization indicate a contradicting relationship – having more evolved signature compared to apatite of both the equigranular monzonite indicating crystallization from a melt which underwent greater feldspar fractionation. Textures show that apatite in the mineralization are anhedral, and has its morphology controlled when bordering ferromagnesian phases. Compositions and textures align with apatite being an intercumulus phase, which crystallized from a liquid which underwent greater feldspar fractionation. However, field relationships, such as steeply dipping mineralization zones do not fit with gravity-driven accumulation. Alternatively, these mineralized zones can be the product of an iron-rich residual liquid. Subsolidus exchange between ferromagnesian phases and Fe-Ti-oxides can drive the compositions of ferromagnesian silicates to higher Mg/Fe ratios. Higher modal proportions of Fe-Ti-oxides in the mineralization zones could result in apparently higher Mg/Fe ratios in clinopyroxene and olivine. Apatite compositions can be used as a fractionation indicator, and the most evolved compositions in the mineralization zones, as well as field relationships, can be used to fit the origins of the mineralization zones with crystallization of a iron-rich residual liquid at the margins of the equigranular monzonite.

About one-fifth of Iceland’s surface is characterized by basaltic volcanic sand deposits. The provenance of the sands, the factors that lead to enrichments from one volcanic source or another, and whether the detritus is representative of the local or regional bedrock is not well understood. Also, basaltic sand regolith is widespread on Mars, and has the potential to provide important information about Mars’ regional volcanic geology, with a more detailed understanding of the sampling and analysis strategies that might be most effective, based on the Iceland sands results. This study investigates the provenance of ten Icelandic volcanic sand surface deposits collected from beach, dune, river levee and glacial outwash settings across the island. This is achieved by analyzing individual grains of sand, and comparing their chemical compositions to samples from the various volcanic systems on Iceland using published and unpublished data sets. The dominant grain types in each sand deposit are basaltic volcanic glass, plagioclase, clinopyroxene, olivine and siliceous volcanic glass. Some or all of these grain varieties have been analyzed from each sample for major and minor elements via electron microprobe analyses (EMPA). The majority of the grains analyzed by EMPA have been analyzed further for trace element concentrations via laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). All ten Icelandic sand samples have also been analyzed in bulk for major, minor, and trace elements via solution inductively coupled plasma optical emission spectrometry (ICP-OES), or inductively coupled plasma mass spectrometry (ICP-MS), depending on the element. The results of the study show that the individual sand grains are commonly linked to two or more relatively proximal (within ~100km) volcanic sources. The volcanic glasses appear to be particularly distinctive provenance indicators. Individual mineral grains are found to be much less distinctive, at least in terms of the major element composition, and generally cannot be linked to a specific volcanic source unambiguously. However, mineral grains that have a chemistry that is anomalous in the context of Iceland can be more reliable indicators of provenance. The composition of the Icelandic sand surface deposits appears to be influenced by several factors. The volcanic sources that have contributed to each sand deposit are almost always explosive volcanic systems, or otherwise have been the site of eruptions having a significant explosive component. Fluvial transport has also had an important effect on the composition of the Icelandic sands, such that when a direct fluvial transport route exists between a given volcanic source and a sample location, volcanic debris from that source is commonly present in the sample. At least in some cases, other factors such as large eruption volume and high eruption frequency have also had an effect on the composition of Iceland’s surface sand. Most of the sands samples under study were found to have compositions that reflect the volcanic geology of the local or regional “volcanic zone” where the sample was collected. When all ten samples are viewed collectively, they provide information about a significant portion of Icelandic regional geology. Implementation of a similar sampling and analysis strategy for the Mars regolith would likely provide a similar level of information about the regional geology of Mars, while limiting collection sites to a few specific dune fields and eliminating the need for bedrock drilling and transportation of heavy cores.

Niobium-yttrium-fluorine (NYF) pegmatites comprise a subset of the rare-element pegmatite class. Because of their composition and geochemistry, these pegmatites are commonly associated with A-type magmatism in extensional environments. NYF pegmatites exposed in the Nordland area of the Norwegian Caledonides have been proposed to be coeval, and genetically related to their 1.7 Ga A-type Tysfjord granitic-gneiss host. A geochronological study, using U-Pb Isotope Dilution Thermal Ionization Mass Spectrometry (ID-TIMS) and Electron-Probe Micro-Analysis (EPMA) total U-Th-Pb techniques applied to zircon, fergusonite and xenotime provide ages of 400 Ma. Petrographic analysis by optical and back-scattered electron (BSE) imaging shows evidence of fergusonite dissolution and growth of xenotime halos around apatite occurring in a fluorine-rich siliceous-melt, and allanite and zircon display primary growth textures attributed to pegmatite emplacement with no evidence of metamorphic overprint. Based on the textural evidence it is proposed that the geochronological data represents the age of primary pegmatite crystallization. This study concludes crystallization of NYF pegmatites through partial melting of their host during late pro-grade metamorphism associated with Caledonian nappe emplacement. Partial melting was likely aided by H2O, made available through local metamorphism, and fluorine, also released by metamorphism of the host. A Caledonian-aged emplacement and crystallization of NYF pegmatites in Nordland challenges the existing model that these pegmatites were part of the host Tysfjord Granite magmatic event. Furthermore, it suggests that the primary model for NYF-pegmatite emplacement that ties them to anorogenic tectonic environments and associated with A-type magmatism may not be appropriate for all cases.

It has been suggested that magmatic structures preserved in plutons may provide information about pluton emplacement and chamber construction; information that is critical for evaluating geochronological data, which indicate that large plutons are gradually emplaced by small magma batches rather than an individual large magma batch. Physical processes recorded in magmatic structures might provide information about the magma conditions prior to solidification, but due to the complexity of formation and petrogenesis of these structures, separating or identifying magma batches on the basis of contact relationships could be very difficult. In this study, major element and trace element variations of hornblende are used to interpret the origins of magmas that formed magmatic structures from Pothole Dome, Tuolumne Intrusive Complex (TIC) and to identify different magma batches and the magmatic processes that led to the complexity of the magmatic structures. Trace element compositions and the variable zoning patterns in hornblende from the magmatic structures cannot be related by fractional crystallization of a single magma batch, nor can they be related by simple magma mixing of two magmas. Instead, the diverse and distinct zoning patterns suggest involvement of at least three magma batches represented by: 1, Hornblende in sample 146B and hornblende 137i-hb4 (reversely zoned, high Ti, Zr, Y, Sr, low Sc, and no concave-up REE patterns); 2, Hornblende in sample 144B, and hornblende crystals 137ii-hb4, 140i-hb1 and 140-137-hb1 (normal zoning with slight to moderate concave-up REE patterns); 3, Hornblende from sample 137, 140i and 140-137 (reversely zoned, low Ti, Y, Zr, Sr, high Sc, and slight to moderate concave-up REE patterns). The compatible behavior of Zr, Sr, and Ba in most of the samples is interpreted to result from crystallization of zircon, plagioclase, potassium feldspar and biotite. The concave-up REE patterns are likely to be caused by sphene crystallization.

Mid-ocean ridges are split into two broad spreading rates: fast and slow. Slow-spreading ridges, which represent 60% of the spreading ridges on Earth, are characterized by exposures of basalt, gabbro, and peridotite. Along some sections of slow-spreading ridges, bathymetric highs characterized by a domal structure are typically bounded by a detachment shear zone/fault that exposed lower crustal and upper mantle rocks. These domal structures are called oceanic core complexes. The formation of the detachment shear zone is synchronous with the formation of the lower oceanic crust, suggesting a fundamental interplay between magmatic and tectonic processes to form the oceanic lithosphere. Therefore, this dissertation focuses on integrating new structural measurements, petrographic observations, and microstructural analysis with electron beam techniques with previously published bulk-rock and mineral compositional variation and borehole imaging to address questions concerning the formation of a discrete 300 m section of crust, the formation and localization of Fe-Ti oxides and their timing relationship with deformation, the orientation and formation of high temperature magmatic and crystal plastic foliations, and the crystallographic preferred orientation of silicate phases in samples with magmatic to crystal plastic fabrics, all from ODP Hole 735B in the Atlantis Bank oceanic core complex, which formed along the Southwest Indian Ridge. In addition, the crystallographic preferred orientation of varitextured gabbros was assessed concerning implications for the formation of two grabbroic bodies recovered from ODP Hole 1256D and a re-orientation study of cores from IODP Hole U1309D from the Atlantis Massif core complex, Mid-Atlantic Ridge. Atlantis Bank is an ideal location to answer the questions above or several reasons, including: 1) over 1.5 km of core was recovered with an average recovery rate of ~87%; 2) relatively low amounts of alteration; 3) rapid cooling preserving high temperature microstructures; 4) onboard measurement of structural features (e.g., fractures, veins, magmatic fabrics, crystal plastic fabrics) from 500-1500 mbsf; and 5) several post-cruise studies completed on rocks from ODP Hole 735B, especially mineral compositional variation. This study demonstrates the importance of utilizing previously collected data provided by the International Ocean Discovery Program (IODP) and integrating new observations to answer questions about the formation of high temperature fabrics and the lower oceanic crust. However, there are limitations in the datasets provided by IODP as most datasets are collected to overall characterize the core recovered, and not to answer the questions posed here. These results demonstrate that models of oceanic core complexes are too simple or broad and more detailed work is needed to address questions associated with the formation and evolution of oceanic core complexes.

Monazite is a light rare earth element orthophosphate with the general formula (LREE)PO4 that may incorporate Th (and U) in its crystalline structure. This had led to monazite’s application in geochronology, and more recently as a petrochronometer. Despite the wide and varied interest in monazite as a petrochronometer much work on the role of fluid composition on monazite stability has been experimental, whilst studies of natural systems have been restricted in terms of the diversity of fluid and rock compositions. The research in this study aims to apply and determine whether the experimentally derived constraints on monazite behavior as a function of fluid composition are applicable and representative geologic environments, as pertains to the monazite growth, composition and solubility, as well as mobility of the rare earth elements. In the Lamoille Canyon area much of the existing geochronology has been conducted on zircon. This proves to be problematic due to high U abundances and subsequently, metamictization of many zircon. This may be compensated for by chemical abrasion. Monazite on the other hand, is well known for its self-annealing properties and rarely shows evidence of metamictization. In the Ruby Mountains and East Humboldt Range, it allows for geochronological work to be conducted without the need for chemical abrasion and the potential pit-falls it introduces. Equi-granular gneiss samples from Lamoille Canyon in the Ruby Mountains-East Humboldt Range metamorphic core complex show three periods of thermal activity since the Cretaceous: 84-90 Ma, 65-80 Ma, and 30-40 Ma. The Ballachulish Igneous Complex and its thermal aureole are located in Western Scotland. The Ballachulish Igneous Complex and its metamorphic aureole provide a contrasting study area where a variety of contrasting metasedimentary lithologies have strikes oriented sub-perpendicular to the contact with the igneous complex. Analysis of monazite textures from this study and other suggest that there were differing fluid regimes in the thermal aureole. Trace element analysis of monazite led to the identification of four populations 467 ± 4 Ma, 450 ± 3 Ma, 431 ± 3 Ma, and 414 ± 2 Ma in samples from the thermal aureole.

Recent high-precision geochronological studies have shown that many large plutonic bodies were emplaced over a span of thousands to millions of years; however, thermal models suggest that these plutons cannot remain molten on these time scales. The shorter time spans for emplacement has led to the hypotheses that large plutonic suites are composed of smaller, distinct magma batches. One possible consequence of batch-wise magma emplacement in the upper crust is that magmatic processes such as fractional crystallization and magma mixing are less effective than they would be in deeper crustal levels. In this study, trace element compositions of hornblende and pyroxene from the stages of the English Peak pluton are used to refine the sequence of emplacement and magmatic history outlined by Schmidt (1994) and will be used to identify magmatic processes that affected the English Peak pluton and if those processes occurred at the depth of emplacement or at a deeper level. Trace element abundances and trends in hornblende from the English Peak pluton indicate that the early, border, Yellow Jacket Ridge, and Chimney Rock stages cannot be related by fractional crystallization or magma mixing at the level of emplacement. Instead, the pluton formed by successive emplacement of multiple magma batches. The diversity of hornblende compositions identified in samples from the early stage of the English Peak pluton cannot be explained by fractional crystallization of a single parental magma or by mixing of two end member magmas. Therefore, it is probable that the early stage formed by emplacement of multiple small magma batches. Trace element abundances and trends in hornblende from the border, Yellow Jacket Ridge, and Chimney Rock stages suggest that the fractional crystallization occurred within magmas of each stage at the depth of emplacement. Some workers have suggested that if intrusive suites are constructed by emplacement of small magma batches, then magmatic processes such as fractional crystallization and magma mixing should be limited to individual batches and may have limited effect at the level of emplacement. In both cores and rims, trace element zoning indicates that, at least, fractional crystallization occurred at the depth of emplacement and deeper in the crust. Fractional crystallization at the depth of emplacement suggests that whatever the size of individual magma batches, fractional crystallization did occur. Likewise, evidence for fractional crystallization at deeper levels indicates that English Peak magmas were derived from middle and/or lower crustal reservoirs in which fractional crystallization +/- magma mixing could occur.

A comparative analysis of xenolith size and shape versus frequency was conducted on datasets collected from four granodioritic plutons: 1) Jackass Lakes pluton, CA (n=104 metavolcanic/metasedimentary xenoliths, 0.001-1.0 km2); 2) Andalshatten batholith, Norway (n=103 meta-calcareous xenoliths, 0.001-1.0 km2); 3) Vega intrusive complex, Norway (n=1069 metasedimentary xenoliths, 0.001-1.0 m2); and 4) English Peak pluton, CA (n=31 metasedimentary xenoliths, 0.01-50 m2). The initial hypothesis is that host rock xenolith size-populations follow a predicted fractal size-distribution relating host rock xenolith size-populations to the fragmentation mechanism of stoping while non-fractal distributions are the result of diking. This hypothesis assumes that stoping, like many other fragmentation processes of Earth materials, yields size-frequency populations related by a power-law function, following the theory of fractal fragmentation. Results of size-frequency distributions from the four locations display a general non-fractal trend over the entire population, with tails defined by a change in slope in the smallest and sometimes largest size categories. Assuming the theory of fractal fragmentation holds true for xenoliths fragmented by stoping and that temperature conditions in the early stages of pluton emplacement will favor stoping, there is an obvious size problem in measured xenolith suites. A size problem is a product of a lack of certain sizes, particularly small sizes, which prohibit a linear trend from defining a population within a log-log plot of cumulative frequency versus size. We postulate this size problem may be due to: 1) observational bias, 2) assimilation, 3) size effect, 4) a change in the mechanism of fragmentation, 5) a change in the physical property of the host rock, 6) composite fragmentation episodes calculated as a single population, or any combination of the above. Results of shape-frequency analysis revealed the most common and average axial ratio was ~0.50 across all four populations, which corresponds to an elongate shape. Since axial ratio measurements are generally consistent across locations, shape characteristics are shown to be independent of size and potentially independent of fragmentation history. Defining these size and shape-population trends through correlation with specific processes of xenolith fragmentation and incorporation may add a quantifiable parameter further illuminating the physical and chemical affects host rock xenoliths may have on the physical and chemical evolution of magma chambers in the crust.

The Jurassic Chetco complex, Josephine ophiolite, and Grayback pluton, all located in the Klamath Mountains, Oregon were interpreted as an arc-backarc-remnant arc assemblage (Harper & Wright, 1984). The Klamath Mountain province is a well-exposed and well-preserved region in which to study subduction-related crust-forming processes, an important mechanism by which new continental crust is generated (Snoke and Barnes, 2006; Condie, 1989; Gill, 1981). Ages of the Chetco complex (155-160Ma; Yule, 1996), Josephine ophiolite (162-165Ma; Harper et al. 1994), and Grayback pluton (157 to 160Ma; Hotz, 1971; Barnes, et al., 1992; Allen and Barnes, 2006) indicate that these magmatic units were coeval and were separated by the intra-arc or back-arc Josephine ophiolite above a single west-facing subducting plate (Harper & Wright, 1984). Many of the rocks from the two complexes are cumulates, making it difficult to determine whether the distinct chemical trends are due to accumulation or to differences in parental magma compositions (e.g., McBirney and Hunter, 1995). Petrographic observations and geochemistry indicate that augite is an early crystallizing phase in all three units. Because augite can incorporate a number of trace elements into its crystal lattice (Blundy & Wood, 2003; Claeson et. al 2007; Cherniak and Liang, 2012; Coint, 2012), it is possible to characterize melt compositions using published partition coefficients and major and trace element data. Rare earth element patterns of calculated melts in equilibrium with augite show three distinct patterns. The Chetco complex has low-K tholeiitic to MORB patterns, the Josephine ophiolite has MORB to E-MORB patterns, and the Grayback pluton has calc-alkaline patterns. These patterns are similar to magma compositions erupted in the volcanic arc, back arc basin, and remnant arc of the modern Tonga-Kermadec Ridge-Lau Basin-Lau-Colville Ridge suprasubduction zone complex. The bulk rock geochemistry of the Chetco-Josephine-Grayback samples in terms of Hf:Th:Ta, Ba/La, La/Nb and Ba and Ta ratios are consistent with emplacement in a suprasubduction zone setting and show similarities to the Tonga-Kermadec Ridge-Lau Basin-Lau-Colville Ridge. Zoning of compatible and incompatible trace elements in augite indicates that the Chetco complex melts evolved by fractional crystallization. The Rogue Formation, previously thought to be the volcanic equivalent of the plutonic Chetco complex, is not related to the Chetco complex based on the differences in compatible element contents in augite; however incompatible element concentrations suggest a common mantle source for these two units. Zoning in some high-Mg# augite from the Grayback pluton suggests possible recharge and mixing of primitive magma during fractional crystallization.

Monazite abundances and textures, and whole-rock compositions are documented and interpreted as a function of temperature and fluid availability in two transects of the Creran Succession and one transect in the Appin Quartzite-Ballachulish Slate transition series in the aureole of the Ballachulish Igneous Complex, Scotland. In a transect sub-perpendicular to the regional foliation of the Creran Succession, FeO and MgO increase with increasing SiO2, while Al2O3 decreases. There are no systematic changes in major element abundances with temperature, although REE abundances show a slight decrease with increasing temperature. In a transect parallel to foliation, FeO and MgO increase while Al2O3 and SiO2 decrease with increasing temperature. REE abundances increase from regionally to thermally metamorphosed samples, reaching a maximum at 615°C and remaining nearly constant thereafter. The third transect, collected foliation parallel in the Appin Quartzite-Ballachulish Slate transition series, has increasing FeO and MgO and decreasing Al2O3 with increasing SiO2 content, but no systematic variations in bulk rock compositions or REE abundances with temperature are observed. Monazite abundances are relatively low in the lowest grade rocks (0.00042-0.00118% Vol.), variably increase from 550-600 ˚C, and are generally ≤0.00217% Vol. at ~600°C. In samples metamorphosed at >600°C, an increase in monazite abundances occurs in all transects (≤0.013% Vol.). From regional grade through ~610°C in rocks of the Creran Succession transect collected foliation-parallel, monazite occurs as individual grains or inclusions. In equivalent rocks of the other transects, monazite occurs as elongate clusters and commonly in association with biotite. Monazite above 610°C in all transects shows no systematic variation in grain size or distribution. Monazite occurrence and abundance correlate with temperatures through 600-620°C, but not necessarily with whole-rock major or rare earth element abundances. In the Creran Succession, the transect parallel to foliation shows increased monazite abundances with higher REE abundances. However, in the transect sub-perpendicular to foliation the pattern is non-systematic. This suggests that there is a second-order process or REE-mineral controlling the local distribution and abundance of monazite.

The 475 Ma Vega intrusive complex is part of the Bindal Batholith in north-central Norway. The complex compositionally zoned from east to west and is composed of the Ylvingen biotite granite, Vega granodiorite, and Fugleværet granodiorite units. Intrusive migmatite and quartz diorite are present along the northern contact of the complex where they intrude host rocks to the complex. Granodiorite and granite are peraluminous to strongly peraluminous, calcic-alkali–calcic, and magnesian, contain sillimanite, garnet, and cordierite, and metasedimentary, meta-igneous, mafic magmatic and ultramafic enclaves. Initial 87Sr/86Sr ratios for plutonic and intrusive migmatites range from 0.708 to 0.742 and εNd values range from -7.0 to -11.0. Granitic rock compositions, phases, and isotopic ratios are those of a classic “S-type” intrusion. Disrupted mafic dikes, mafic magmatic enclaves, and amphibolite enclaves are alkali–calcic, magnesian, metaluminous, and have isotopic and trace element abundances indicating a depleted mantle origin. Isotopic mixing models indicate that peraluminous and mafic rocks did not mix although enclave textures suggest that these magmas mingled. Metasedimentary host rocks to the complex are part of the Helgeland Nappe Complex in the Uppermost Allochthon of the Norwegian Caledonides. The polydeformed (D1–D3) rocks contain folded intrusive migmatitic dikes, suggesting that the complex was syntectonically emplaced during regional D3 deformation. Contact migmatitic rocks contain the assemblage muscovite + biotite + quartz + plagioclase+ K-feldspar + kyanite + staurolite + garnet which indicate that the host rocks followed a Barrovian prograde P–T path associated with crustal thickening that began prior to emplacement of the complex. Garnet-aluminosilicate-silica-plagioclase barometry resulted in estimates of emplacement pressures of 750 MPa on the eastern side the complex, whereas cordierite and muscovite on the western side of the complex formed at pressures between 500 MPa and 350 MPa. The range of pressures across the entire complex is interpreted as due to westward tilting of the crustal section (~20 degrees) exposing ~9.6 km of structural relief through the complex. Vega granodiorite was emplaced across a regional structural boundary. Magmatic layering east of the boundary strikes ~N40E and dips moderately to the east, whereas magmatic layering on the west side of the boundary broadly strikes E–W. Layering orientations on either side of the boundary are similar to corresponding regional host rock gneissic banding and foliation. Magmatic layering is primarily defined by a variation in the modal abundance of biotite. Accumulation of biotite and restitic or early crystallizing phases was induced by shearing between magma and host rocks that caused crystal-melt separation as magmas were emplaced as sheets into the pre-existing host rock structures. Metasedimentary enclaves with equivalent host rocks that are elongate parallel to layering and have foliation and banding aligned with regional host rock structure are interpreted as screens or xenoliths that are probably in situ. The maximum abundance of enclaves in the complex is ~12% and an even smaller proportion of enclaves have equivalent host rocks which implies that a significant proportion of host rocks have been removed to make space for the complex. Limited host rock deformation in the contact aureole, concordant and discordant pluton-host rock contacts, and the orientation of layering and screens indicate that magma emplacement was accommodated by sheeting and stoping with a small amount of host rock flow. Most (99%) of the enclaves in the Vega intrusive complex are metasedimentary types and have either come from the Paleozoic part of the Horta nappe or from the host rocks to the complex. Some enclaves, such as quartzofeldspathic gneiss (blue-gray gneiss), biotite-rich schist, biotite quartz plagioclase gneiss, and migmatite are also present in the anatectic granites in the Paleozoic part of the Horta nappe. These enclaves lack host rock equivalents, are interpreted to be residual in character, and to have a source in the Paleozoic part of the Horta nappe. Calc-silicate and quartzite xenoliths have host rock equivalents, occur in swarms, and are absent or are a minor component of the Horta nappe. Biotite-rich enclaves lack muscovite and plagioclase, suggesting that they formed by muscovite or biotite dehydration melting reactions and are “restitic” whereas residual gneiss and migmatite enclave compositions are similar to those of Vega and Fugleværet granodiorite rocks. Mafic magmatic enclaves mingled with anatectic granite in the Paleozoic gneisses of the Horta nappe and equivalent enclaves are present in the Vega intrusive complex. Formation of enclave trains, emplacement of magma in sheets, elongate enclaves, the distribution magmatic structures, the E–W elongate shape of the complex, and the emplacement of biotite granite to the east and Fugleværet granodiorite to the west of the Vega granodiorite are consistent with emplacement of the complex during regional extension and suggest that crustal thickening ceased prior to emplacement of the complex. Bimodal magmatism and emplacement of the complex during regional extension occurred in a volcanic arc environment in which slab-roll back associated with west-directed subduction collapsed the arc or back-arc against or near the Laurentia margin, resulting in crustal thickening, poly-phase deformation of ocean basin sediments, and the imbrication of slivers of ophiolite and ultramafite prior to emplacement of the Vega intrusive complex. Under- or intraplating of mafic magmas along with muscovite- and biotite-decompression melting aided in anatexis of the source rocks and formed residual biotite schist, migmatite, and gneissic enclaves that ascended with anatectic magmas. Magma was emplaced by splitting pre-existing host rock structures. Incorporation of host rock xenoliths and screens created a “ghost structure” and “ghost stratigraphy” within the complex. S-type magmatism in the region was followed by emplacement of subsequently younger pulses of calc-alkaline magmas in the Bindal Batholith that are principally located on the eastern side of the batholith.

The Ruby Mountain–East Humboldt Range metamorphic core complex is one of a series of cordilleran complexes that span the western half of North America. At least four generations of peraluminous granites have been identified in the Ruby Mountains, three of which are geochronologically well constrained. One unit, a pegmatitic granitic gneiss, has yielded a more complex U-Pb dataset that presents challenges for interpretation of its age and origin. A ~50 M.y. span of dates have been reported from this pegmatitic granitic gneiss unit suggesting that there has been a prolonged period of thermal activity as well as the production of multiple low temperature granitic melts within the same geographic region. Textural complexity in zircon from the pegmatitic granite reveals a wealth of geochemical information that has been used to interpret how this granitic system evolved through time. A significant factor in understanding complex igneous systems is the application of high precision geochronological techniques that enable the time scales of magma emplacement and crystallization to be measured. Accurate measurements of elements such as U, Th, Pb, Hf and REE provide a mechanism for interpreting conditions of zircon crystallization (Hoskin and Schaltegger, 2003) giving insight into the ongoing debate on the origins of granitic melts and magmas. The application of chemical abrasion techniques is shown in this study to improve the accuracy of in situ micro-analysis, eliminating some of the difficulties associated with zircon analysis and the interpretation of the data. U-Pb analysis for pegmatitic granites displaying discrete crystallization periods at 75-71 Ma and 40-36 Ma and observable migmatitic textures in the field, coupled with evidence for dissolution-reprecipitation, suggest that the coarse more leucocratic units from Lamoille Canyon represent in situ partial melts (leucosome) of the preexisting finer banded Cretaceous granite gneiss (paleosome).

A carbonatite-hosted rare earth element (REE) deposit is located in the Bear Lodge Mountains of northeast Wyoming. The carbonatite is emplaced as subvertical, northwest-trending dikes primarily situated within three diatreme structures. The carbonatite dikes of interest are located outside the northern boundary of the Bull Hill diatreme: northwest Bull Hill. These dikes trend north-south and have lower ore grades than dikes within the Bull Hill diatreme. Alkaline silicate rock units, which are the predominant igneous rock type in the Bear Lodge complex, are temporally and spatially related to carbonatite dike intrusions. This type of association is common for carbonatite intrusions worldwide and may indicate a genetic relationship exists between carbonatite and alkaline silicate magmas. The northwest Bull Hill carbonatite is composed primarily of fine-grained, anhedral calcite, coarse-grained, consertal calcite, coarse-grained, subhedral to euhedral calcite and from

Modalities of batholith assembly within the crust are still debated. Numerous studies conducted over the past 60 years suggest that processes such as fractional crystallization, assimilation, or mixing can account for a lot of the chemical variations associated with intrusive suites. Recent U-Pb geochronology data obtained on zircon show however that some of the cordilleran batholith can b emplaced over several millions of years. Emplacement of large intrusion is now thought to be an incremental process, based on the thermal models which indicate that even large batches of magma cannot remain above their solidus more than a couple million of years. In these models, small magma batches are emplaced in the crust through a long period of time, limiting the possible interactions between these batches and prohibiting the development of large magma tic reservoirs capable of feeding large eruptions. This goal of this study was to reconstruct the assembly of one of these cordilleran batholith, the Wooley Creek batholith and the Slinkard pluton, which are part of the same magmatic system, in order to characterize and map the size of the magma batches that were once capable of chemically and physically interacting. Two main approaches were taken. The first one, pretty common in the literature, is to use TIMS U-Pb geochronology on zircon to date the various part of the intrusion. Preliminary results indicate that the main part of the Wooley Creek batholith and Slinkard pluton system crystallized over less than 3 m.y. These results do not prohibit the development of a sustainable magma chamber. The second approach consisted on using trace element in rock forming minerals (augite and hornblende in this case) to characterize different magma batches and track their evolution through time. While the lower part of the system is constituted of small magma batches that evolved individually, the upper zone was more homogeneous and the consistency in the hornblende composition throughout the whole unit indicate that it was once a single large batch of magma. Upward zoning with more felsic rocks cropping out at the top of the system can be accounted for by percolation of the differentiated melt through the mush. The presence of roof dikes associated with the upper zone indicates that this part of the system was once eruptible. This study introduce a new technique to study magmatic evolution and characterize the size of the magma batches in the system, which combined with U-Pb geochronology, give a powerful tool to understand pluton assembly and the development of magmatic reservoirs. In the case of the Wooley Creek batholith and the Slinkard pluton it shows that modalities of assembly can differ from one part of the intrusion to another, despite a similar timescale of magma input. Results associated with assimilation processes indicate that the preserved record depends on the size of the magma batch interacting with the assimilated material. In the upper zone, the effect of assimilation is diluted within the large volume of magma, whereas in the central part, where batches are much smaller, it can be easily characterized.

The Wooley Creek batholith is a late Jurassic mid-crustal pluton exposed in the Klamath Mountains of northern California and southwestern Oregon. Metamorphic assemblages in the aureole of the pluton indicate it has been tilted to the southwest, exposing approximately 9 km of structural relief [Barnes et al., 1986b]. Structural mapping in the interior of the pluton combined with previous geochemical and geochronology studies has shown that the Wooley Creek batholith was emplaced in two stages between 158 – 156 Ma. Diapirs of basaltic and andesitic magma began intruding into the accreted terranes of the western Paleozoic and Triassic belt around 158 Ma. Prolonged magmatism allowed these intrusions to amalgamate into a large plutonic body, forming the lower Wooley Creek batholith. The intrusion of these magma batches compressed first the surrounding host rock, forming a narrow structural aureole, then older batches, forming a steeply dipping magmatic foliation. The resulting plutonic mass was both texturally and compositionally highly variable. In the waning stages of emplacement, magmatism reinitiated with an influx of dacitic magma. The dacitic magma intruded through the lower Wooley Creek batholith, pooling at the rheological interface between the partially molten lower Wooley Creek batholith and overlying host rocks. As magma continued to feed into the chamber, it began convecting and stoped upwards. Repeated injection of basaltic magmas throughout this time collected at the floor of the expanding chamber, adding heat and facilitating localized mixing and mingling between the upper and lower Wooley Creek batholith. Chamber-wide convection within the upper Wooley Creek batholith formed margin parallel magmatic fabrics and caused the intrusion to rapidly cool. Subsequent foundering of the upper Wooley Creek batholith deformed the underlying lower Wooley Creek batholith immediately adjacent at hypersolidus conditions. Field relationships suggest that the Wooley Creek batholith is decoupled from host rock structures, and internal fabrics are entirely emplacement-related.

The Chetco complex is a late Jurassic mafic-ultramafic batholith in the northwest Klamath Mountain province of south eastern Oregon. It has previously only been mapped at large scale north of the Illinois River. Mapping of the York Butte quadrangle at 1:24,000 scale indicates that there are two mineralogically and compositionally distinct units: a quartz hornblende gabbro (the Red Dog Creek gabbro) and a two-pyroxene gabbro and troctolite unit (the York Butte gabbro). Both units are intruded by tonalite. Field and textural evidence suggests that a substantial portion of the York Butte gabbro is a cumulate. Smooth compositional trends in major and trace elements as well as inverse rare earth element patterns suggest that both gabbros are related via fractional crystallization from a high-alumina basaltic parent. Trace element patterns are consistent with an island arc setting for the pluton. The two-pyroxene and troctolitic York Butte gabbro forms the core of the pluton and the quartz-hornblende Red Dog Creek gabbro forms the rim. This relationship, with a mafic core and more felsic rim, has been described as a reversely zoned pluton. Characteristics similar to those seen in sheeted plutons such as steep sub-parallel internal contacts and foliations indicate that re-assessment of the pluton’s emplacement history may be necessary. Overlap in most major elements and similarly shaped rare earth element patterns between the Chetco complex and Rogue Formation are consistent with the hypothesis that these units are the plutonic and volcanic portions, respectively, of the same magmatic system.

The 36 Ma Harrison Pass pluton is composed of four units defined by previous studies: the Toyn Creek hornblende biotite granodiorite interpreted as a hybrid, the Corral Creek biotite monzogranite interpreted as the felsic end member of mixing for the Toyn Creek unit, sheets of leucocratic two‐mica monzogranite and the Green Mountain Creek two‐mica monzogranite. Field and petrogenetic evidence for mixing of intermediate magmas and fractionation has been presented. Quartz and titanite provide a record of these processes through trace element encorporation during growth. Using LA‐ICP‐MS, trace elements in quartz and titanite were measured. The TitaniQ thermometer for Ti in quartz and the Zr in titanite thermobarometer were used to estimate temperatures of crystallization. Quartz from the Toyn Creek unit are reversely zoned in calculated temperature, but trace element variation in quartz is insignificant suggesting mixing of thermally distinct, but compositionally similar magmas. Titanite calculated temperature and REE variation is reversely zoned suggesting mixing of thermally and compositionally distinct magmas. Quartz from the Corral Creek and Green Mountain Creek units are normally zoned in calculated temperature and trace elements suggesting the magma was cooling during growth. Trace elements in quartz from the Toyn Creek and Corral Creek units do not overlap, suggesting the Corral Creek unit may not be the felsic end member of mixing for the Toyn Creek unit. Trace elements in quartz from a porphyritic roof dike overlap with quartz compositions from the Corral Creek unit, but the dike is interpreted to originate from the Toyn Creek unit based on bulk‐rock geochemistry and mineral assemblage, suggesting quartz grains from the felsic end member were incorporated by mixing into the hybrid Toyn Creek magma. Trace elements in a phenocryst of quartz from a mafic magmatic enclave overlap with quartz compositions from the Toyn Creek unit suggesting the quartz phenocryst in the enclave oringinated in the Toyn Creek magma. This study shows chemical variation in individual crystals, which is easily overlooked at the whole rock scale, can be used to interpret and constrain magma processes. The calculated temperature and REE variations in titanite suggest magma mixing occurred in the Toyn Creek unit. The calculated temperature and trace element variation in quartz suggests the Toyn Creek unit was assembled in batches. Temperature and trece element zoning in quartz from the Corral Creek and Green Mountain Creek units are consistent with fractional crystallization.

The Upper Pennsylvanian Stark Shale is the core shale of the Dennis cyclothem. Bottom-water oxygenation is an important control on the preservation and quality of sedimentary organic matter and may influence the enrichments of trace elements (TEs). Detailed sample intervals were collected from four cores of the Stark Shale from Nemaha Uplift in Kansas (uplift cores) to the Forest City Basin in Missouri (basin cores). The samples were analyzed for major and trace elements, organic carbon and clay mineralogy. X-ray diffraction showed that illite, quartz and pyrite are the predominant minerals. Detrital elements (Si, Al, Zr and Ti) showed higher abundances of clay in the basin compared to the uplift. The weathering index and chemical index of alteration both indicate that source minerals of the shale were highly weathered. The basin core showed a more mature source compared to the uplift cores. Core shales were deposited during maximum transgression and may have high or low TOC depending on bottom-water oxygen levels. In high TOC cores (TOC > 10 %), abundances of V, Zn, Cr, Ni and Mo showed a moderate to strong correlation with TOC in the basin cores. The Heinen core (uplift) showed no significant correlation with the above elements at high TOCs. Low TOC shale (Emery core) showed no significant correlation with all trace elements (TEs). TEs enrichments were classified into TEs of euxinic affinity (V, Mo) and TEs associated with organic matter (Cu, Ni, Zn). Covariation of TEs of strong euxinic affinity with TOC were observed to be stronger in the basin core. Redox geochemical ratios V/Cr, TEs, V/ (V+Ni) and V-Mo covariation indicate euxinic conditions in the basin. Anoxic ¡V oxic conditions seem dominant in the uplift cores. Rock eval data showed a mixture of type I and II kerogen indicating terrestrial and marine organic matter. These data suggest that the controlling factors in the distribution of elements regionally and stratigraphically within the Stark Shale are: -Degree of weathering before deposition -Paleoredox conditions in the depositional environment -The composition of the organic -Settling time of detrital influx -Paleoclimate and paleogeographic conditions during deposition.

The Hortavær Igneous Complex, off the coast of north-central Norway, is a zoned pluton that exhibits evidence of upward growth as a series of stacked layers or sheets. What crops out now is a pluton with, from west to east, heterogeneous zones of syenite, intense sheeting, diorite, monzonite, and alkali granite. Sheets dip steeply west and strike N-S in the south and N30E in the north, defining the limbs of a regional fold. The pluton intruded calc-silicate, carbonate, and migmatitic gneissic host rocks about 466 Ma. Assimilation and fractional crystallization of dioritic magmas produced syenitic and monzonitic magmas, which are interpreted to have migrated laterally due to outward flow of successive injections of magma. Continued injection of dioritic magma produced more syenite and monzonite. New pulses of diorite spread laterally over variably crystal-rich syenitic magmas. The density contrast between syenitic and dioritic magmas caused syenite to escape upward, producing tubes and flames of syenite that intruded into the overlying sheets. Flame structures in the sheets point to the east, the original top of the pluton. At their bases, dioritic sheets quenched against the syenite and were penetrated by the escape structures. Along their upper surfaces, the dioritic sheets mingled with overlying syenitic magmas to produce enclaves. Magmatic foliation is oriented parallel to the sheets and is defined by alignment of elongate minerals and flattened enclaves. This foliation is interpreted to result from overburden pressure. Folding of the pluton produced parasitic folds of the sheets in the limbs of the regional fold. Subsequent block rotation about 90 degrees east resulted in the current orientation of sheets with a steep westward dip.

Metamorphosed strata of the Sing Peak pendant, central Sierra Nevada, CA, record structures formed during the contemporaneous emplacement of adjacent plutons and regional deformation in the mid-Cretaceous. Host rocks in the Sing Peak pendant consist of deformed metavolcanic rocks of the mid-Cretaceous Minarets Caldera sequence and less common Jurassic metasedimentary rocks. Structures in the Sing Peak pendant include: a) a penetrative, subvertical, NNW-striking foliation defined by stretched phenocrysts and recrystallized biotite, epidote and amphibole; and b) a dextral sense ductile shear zone with a shallow/moderate plunging (~40º) NNW-trending lineation. The shear zone can be traced into the Jackass Lakes pluton along the northeastern and northern margins of the pendant. The Jurassic metasedimentary rocks are locally folded with NNW-striking axial planes and the folds are commonly truncated by the Jackass Lakes pluton. Structures within the Jackass Lakes pluton include a well-developed NNW-striking, steeply west dipping magmatic foliation and a moderately north plunging (~40º) lineation defined by elongated biotite and hornblende phenocrysts. The magmatic structures are continuous across compositional zones within the Jackass Lakes pluton and parallel to the elongated axis of mafic enclaves observed within the pluton. Abundant xenoliths (up to 300 m long) of metavolcanic rocks appear to be concentrated near the roof pendant but are also found throughout the pluton. Metamorphic foliations observed within the xenoliths are sub-parallel with those in the host rocks and the magmatic foliation of the pluton. Some xenoliths contain dikes of the Jackass Lakes pluton, up to 1 m in width, that have been folded with axial planes striking sub-parallel to the metamorphic foliation in the xenoliths, host rocks and magmatic foliations in the pluton. These observations suggest that the magmatic and metamorphic foliation as well as the folded dikes were formed during chamber construction and most likely due to regional deformation. Based on the lineation data, the deformation in the ductile shear zone and the ~ 98 Ma Jackass Lakes pluton is the result of regional transpression. Previous work has suggested that regional dextral transpression was not initiated until ~ 90 Ma in the central Sierra Nevada. Therefore, the Jackass Lakes pluton – host rock system represents the earliest documented regional dextral transpression in the central Sierra Nevada.

Recent studies have shown that stable carbon and oxygen isotope analyses of soil carbonate (caliche) are useful in paleoenvironmental reconstructions. The Ogallala Formation of the Southern High Plains contains widespread caliche profiles, making it an ideal target for such studies. The "caprock caliche" (early Pliocene) is an erosion-resistant soil carbonate layer that marks the top of the Ogallala Formation. Three sections of the "caprock" were chosen for this study. Samples were taken from outcrops near Crosbyton in Crosby County, Texas, near Lamesa in Dawson County, Texas, and near Ragland in Quay County, New Mexico. The Crosby County profile was the primary section used in this study. Samples were taken in 10 em intervals along vertical transects through the nodular, massive, and laminated zones. The o13C values from this profile range from -4.3 to -7.2o/oo for the carbonate and -21.7 to -26.1%o for the organic matter. These values suggests that C3 flora was favored in this region at the time of formation of the "caprock" caliche, with a slight trend towards increased c4 flora. Similar results are seen at Lamesa and Ragland. Oxygen isotope analyses of the Crosby County section yield 0180 values ranging from -4.4 to -5.6%o, with a standard deviation of 0.3%o. This suggests that either relatively uniform climatic conditions existed in the region when the "caprock" formed, or that the oxygen isotopes are not sensitive enough to show the temperature change necessary to cause the slight variation in vegetation.

Stable carbon and oxygen isotopic ratios were measured for caliche horizons in the Blackwater Draw Formation, at Blanco Canyon, in order to determine the paleoclimatic history of the Southern High Plains for approximately the past 1.6 Ma Carbon isotopes were analyzed to determine the proportion of C4 to C3 vegetation, and possible soil conditions at the time of carbonate formation. It was found to be quantitatively difficult to determine the fraction of c4 to c3 vegetation once supported by the Blackwater Draw Formation paleosols, however it has likely varied from less than 50% C4 prior to 1.6 Ma up to as much as 80% C4 in more recent times. Modeling of paleosol conditions suggested that the caliches formed under low soil C02 concentrations, which resulted from sparse surface vegetation giving rise to low soil respiration rates and allowing for a higher influence of atmospheric C02 • Oxygen isotopes were analyzed in order to calculate paleometeoric water compositions and to determine primary sources for precipitation on the Southern High Plains. Measured ~180 compositions suggest that the oxygen isotopic composition of precipitation has not changed drastically over the past 1.6 Ma and modem precipitation for the Southern High Plains is more depleted in 180 relative to values calculated in this study. It is suggested that pre-Holocene atmospheric circulation patterns, over the Southern High Plains, were similar as today but allowed for a higher influence of precipitation from Gulf moisture.