The Deccan Trap basalts are the remnants of a massive series of lava flows that erupted at the K/T boundary and covered 1-2 million km2 of west-central India. This eruptive event is of global interest because of its possible link to the major mass extinction event, and there is much debate about the duration of this massive volcanic event. In contrast to isotopic or paleomagnetic dating methods, I explore an alternative approach to determine the lifecycle of the magma chambers that supplied the lavas, and extend the concept to obtain a tighter constraint on Deccan’s duration. My method relies on extracting time information from elemental and isotopic diffusion across zone boundary in an individual crystal. I determined elemental and Sr-isotopic variations across abnormally large (2-5 cm) plagioclase crystals from the Thalghat and Kashele “Giant Plagioclase Basalts” from the lowermost Jawhar and Igatpuri Formations respectively in the thickest Western Ghats section near Mumbai. I also obtained bulk rock major, trace and rare earth element chemistry of each lava flow from the two formations. Thalghat flows contain only 12% zoned crystals, with 87Sr/86Sr ratios of 0.7096 in the core and 0.7106 in the rim, separated by a sharp boundary. In contrast, all Kashele crystals have a wider range of 87Sr/86Sr values, with multiple zones. Geochemical modeling of the data suggests that the two types of crystals grew in distinct magmatic environments. Modeling intracrystalline diffusive equilibration between the core and rim of Thalghat crystals led me to obtain a crystal growth rate of 2.03x10-10 cm/s and a residence time of 780 years for the crystals in the magma chamber(s). Employing some assumptions based on field and geochronologic evidence, I extrapolated this residence time to the entire Western Ghats and obtained an estimate of 25,000 – 35,000 years for the duration of Western Ghats volcanism. This gave an eruptive rate of 30 – 40 km3/yr, which is much higher than any presently erupting volcano. This result will remain speculative until a similarly detailed analytical-modeling study is performed for the rest of the Western Ghats formations.

The aim of thesis was to establish a methodology for 210Pb measurements by Accelerator Mass Spectrometry (AMS). The potential application is to measure 210Pb in people who have been exposed to radon. This will better our understanding of radon toxicity, which is not possible now with current radiometric and mass spectrometry techniques. The determination of 210Pb by AMS was done in two major studies 1) Studying Pb chemistry in a Cs+ sputter source used in AMS and 2) Evaluating 204,205 & 208Pb spikes for the quantification of 210Pb by isotope dilution. Pb chemistry was investigated using an 834 SIMS-type and a SO-110 Cs+ sputter source at the IsoTrace Laboratory and A.E Lalonde AMS facility, respectively. Different molecular anions of Pb were studied with the 834 SIMS-type Cs+ sputter source and the strongest molecular anion current of Pb and thus greatest ionization efficiency was achieved form the superhalogen PbF3-. The average 208PbF3- current was unaffected by varying the ratio of the fluorinating compounds (AgF2 and CsF) packed into a target. The average current of 208PbF3- was reproducibly increased by chemically mixing the targets of AgF2, CsF and PbF2 in concentrated HF rather than mechanically mixing them the powders with a stir rod. The count rate of 210Pb reproducibly increased by a factor of 20 when μg quantities of PbF2 were present in mg AMS targets compared to AMS targets that had pg quantities of PbF2. The average current of 208PbF3- for pure PbF2 targets in an SO-100 Cs+ sputter source was reproducibly increased when the Cs+ flux was decreased by a factor of 10. This phase of my work maximized the overall efficiency of PbF3-, to a value of 1.8x10-10 ±8x10-11s-, which was a key first step in the measurement by AMS. Then isotope dilution was tested to quantify 210Pb and the next stage of my work evaluated the use of 204,205 & 208Pb spikes. 210Pb was measured in the +3 charge state by isotope dilution assays using 204,205 & 208Pb spikes. 204Pb+3 reproducibly suffered from the molecular interference from 68Zn3+3, which could not be easily removed without negatively impacting the detection limit for 210Pb. 205Pb+3 continually suffered from 205Tl+3 interference which could be readily be removed but not without negatively affecting the II detection limit for 210Pb. 208Pb+3 suffers from no molecular interferences but if a large amount of 208Pb is needed to swamp the Pb in a sample, this could limit the detection limit for 210Pb as the abundance sensitivity is 210Pb/208Pb=1.3×10-12. A calibration curve is required when 208Pb is used as a spike due to a difference in collection efficiency of a Faraday cup, where 208Pb+3 is detected and the gas ionization chamber, where 210Pb+3 is detected. The quantification of 210Pb with 208Pb as a spike yielded a detection limit of 4.4mBq at the IsoTrace facility. A theoretical detection limit of ≤0.11mBq is expected at the A.E Lalonde AMS facility. The expected detection limit at the A.E Lalonde AMS facility is on par with α-spectroscopy but AMS samples can be counted in less than 1 hour whereas alpha spectrometry samples must be counted for about 1 day.

The tuff of Elevenmile Canyon (TEC) is a 25.1 Ma trachydacite to rhyolite intracaldera tuff produced by the largest of 6 Oligocene overlapping calderas that, along with related plutons, constitute the Stillwater Caldera Complex, one of the largest eruptions of the Western Nevada Volcanic Field during the mid-Tertiary ignimbrite flare-up. Typically crystal-rich with a mineral assemblage of plagioclase > quartz  sanidine > biotite ± hornblende and clinopyroxene, there are two discernable pumice types throughout the tuff: a lighter crystal-rich pumice and a darker, commonly aphyric pumice type. Rb-Sr and Sm-Nd isotopic compositions of pumice fragments and whole rock samples indicate an enriched mantle component (87Sr/86Srin = 0.70495 – 0.70535, Nd[t=25.1Ma] = -1.13 to -0.39) similar to that of coeval Cenozoic mafic lavas. Pb isotopes (206Pb/204Pbin = 19.042 – 19.168, 207Pb/204Pbin = 15.557 – 15.664) fall along a tight trend between the Northern Hemisphere Reference Line (Hart 1984) and an endmember similar to local granitic units. Major and trace element modelling support a source for the TEC derived from the mixing of anatectic melts of crustal rocks with intruded mantle-derived magmas similar to a local basaltic-andesite.

High precision measurements of Ti isotopes within terrestrial and extra-terrestrial materials were made in order to investigate the processes at work within the early solar system. Variations of Ti isotopes also enabled the investigation of the specific stellar sources that created the material that formed the solar system. Titanium was chosen as it is a refractory element, relatively resistant to secondary processes and found abundantly in all solar system materials. Measurements were performed using a Thermo Fischer Neptune MC-ICPMS at the Open University, Milton Keynes. Various samples of carbonaceous chondrites, ordinary chondrites, enstatite chondrites, achondrites, lunar, terrestrial and early solar system components were analysed. Mass independent measurements of various solar system materials revealed a correlation between ε50/47Ti49/47 and ε46/47Ti49/47 defining a best line with a slope of 5.34 ± 0.34. The correlation indicates that solar system materials contain nucleosynthetic components that match a SNII stellar source. Utilising aliquots previously analysed for Zr isotopes for Ti isotope analyses revealed a correlation between ε50/47Ti49/47 and ε96/90Zr94/90 for the carbonaceous chondrites that is controlled by the CAI content of the particular carbonaceous chondrite group. Step wise dissolution of ordinary chondrites and carbonaceous chondrites revealed multiple nucleosynthetic Ti components contributing to the solar system. Stepwise leachate dissolutions were conducted on the carbonaceous chondrites Allende, Murchison and Orgueil to compliment the study of the same samples for Zr by Schönbächler et al. (2005). In addition, sample aliquots of QUE 97008 and Murchison from the work of Qin et al. (2011) were also investigated for Ti. The two investigations allow the comparison of Ti in different phases to be compared with other isotope systems such as Zr (Schönbächler et al. 2005) and Cr, Sr, Ba, Sm, Nd and Hf (Qin et al. 2011).Mass dependent fractionation and absolute nucleosynthetic anomalies of Ti within solar system materials was determined by utilising the double spike procedure. Mass dependent analysis enabled the Stable isotope composition of terrestrial materials to be investigated, revealing mass dependent fractionation between terrestrial basalts and andesite’s. Utilising the double spike procedure also enabled the calculation of absolute nucleosynthetic anomalies for Ti within solar system materials. The absolute nucleosynthetic anomalies data revealed that CAI’s contain two different compositions with one representing an exotic stellar source and the other representing the mainstream solar system composition.

Among-individual variation in resource use is pervasive and may have ecosystem-wide effects. This variation between individuals can affect population niche breadth. My study determined if niche breadth was best explained by dispersal of individuals from locations with different prey resources driven by ecosystem level disturbance regimes or competition among individuals inhabiting a site, resulting in dietary partitioning. I used structural equation modeling to examine the direct and indirect effects of several environmental variables spanning gradients of disturbance, competition strength, and food availability on niche breadth of the Eastern Mosquitofish (Gambusia holbrooki). I evaluated two complementary models 1) allowing for only direct effects of disturbance on niche breadth and 2) limiting effects of disturbance on niche breadth to indirect effects via food availability and competitor densities. The partitioning hypothesis excluding direct effects of disturbance on niche breadth was best supported by my data.

Cotton is the most abundant natural fiber in the world. Many countries are involved in the growing, importation, exportation and production of this commodity. Paper documentation claiming geographic origin is the current method employed at U.S. ports for identifying cotton sources and enforcing tariffs. Because customs documentation can be easily falsified, it is necessary to develop a robust method for authenticating or refuting the source of the cotton commodities. This work presents, for the first time, a comprehensive approach to the chemical characterization of unprocessed cotton in order to provide an independent tool to establish geographic origin. Elemental and stable isotope ratio analysis of unprocessed cotton provides a means to increase the ability to distinguish cotton in addition to any physical and morphological examinations that could be, and are currently performed. Elemental analysis has been conducted using LA-ICP-MS, LA-ICP-OES and LIBS in order to offer a direct comparison of the analytical performance of each technique and determine the utility of each technique for this purpose. Multivariate predictive modeling approaches are used to determine the potential of elemental and stable isotopic information to aide in the geographic provenancing of unprocessed cotton of both domestic and foreign origin. These approaches assess the stability of the profiles to temporal and spatial variation to determine the feasibility of this application. This dissertation also evaluates plasma conditions and ablation processes so as to improve the quality of analytical measurements made using atomic emission spectroscopy techniques. These interactions, in LIBS particularly, are assessed to determine any potential simplification of the instrumental design and method development phases. This is accomplished through the analysis of several matrices representing different physical substrates to determine the potential of adopting universal LIBS parameters for 532 nm and 1064 nm LIBS for some important operating parameters. A novel approach to evaluate both ablation processes and plasma conditions using a single measurement was developed and utilized to determine the “useful ablation efficiency” for different materials. The work presented here demonstrates the potential for an a priori prediction of some probable laser parameters important in analytical LIBS measurement.

abstract: Meteorites and their components can be used to unravel the history of the early Solar System. Carbonaceous chondrites are meteorites that originated from undifferentiated parent bodies that formed within a few million years of the beginning of the Solar System. These meteorites contain calcium-aluminum-rich inclusions (CAIs), which are the oldest dated solids in the Solar System at ~4.567 billion years old and thus preserve a record of the earliest stage of Solar System formation. The isotopic compositions of CAIs and bulk carbonaceous chondrites can be used to identify the sources of material inherited by the protoplanetary disk, assess the degree of mixing in the disk, and evaluate sample origins and potential genetic relationships between parent bodies. In particular, mass-independent Cr and Ti isotopic compositions have proven to be especially useful for these purposes. In this work, I first developed new methods for the chemical separation of Cr and Ti, improving the reliability of existing methods to ensure consistent yields and accurate isotopic measurements. I then measured the Cr and Ti isotopic compositions of CAIs from CV and CK chondrites to determine the extent of isotopic heterogeneity in the CAI-forming region and assess the role of CAIs in the preservation of planetary-scale isotopic anomalies. My results show that all measured CAIs originated from a common isotopic reservoir that incorporated material from at least three distinct nucleosynthetic sources and preserved limited isotopic heterogeneity. These results also suggest that planetary-scale isotopic anomalies cannot be attributed solely to the transport of CAIs from one part of the solar nebula to another. I finally measured the Cr and Ti isotopic compositions of bulk CM, CO, and ungrouped chondrites to evaluate the relationship between CM and CO chondrites, which have been suggested to originate from either distinct but related parent bodies or a common compositionally heterogeneous parent body. My results suggest that CM, CO, and related ungrouped chondrites originated from distinct parent bodies that formed from similar precursor materials in nearby formation regions. These results may have implications for asteroid samples returned by the OSIRIS-REx and Hayabusa2 missions. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2020

京都大学 / 新制・課程博士 / 博士(地球環境学) / 甲第23351号 / 地環博第209号 / 新制||地環||40(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 德地 直子, 教授 柴田 昌三, 准教授 西川 完途 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DGAM

The Saglek-Hebron Complex (SHC) in Northern Labrador represents one of the oldest terrains on Earth and it is closely related to the Archean Itsaq Gneiss Complex (IGC) in Greenland. The SHC is a typical granite-greenstone terrain that recorded over one billion years of magmatic history between ~3900 Ma and ~2700 Ma. Our geochronological and geochemical study shows that the SHC includes five generations of trondhjemite-tonalite-granodiorite suites (TTG): the ~3870 Ma Iqaluk gneiss, the ~3750 Ma Uivak I gneiss, the ~3600 Ma Uivak II gneiss, the newly described ~3300 Ma Iluilik gneiss, and the ~3220 Ma Lister gneiss. These granitoid units are mostly consist of trondhjemite and tonalite with only rare granodiorites that appear to define a distinct unit formed at ~3330 Ma and newly defined as the Iluilik gneiss. The Iluilik granodiorite appears to be derived from a Hadean mafic crust as supported by its combined whole-rock geochemical composition, its positive µ142Nd value of +6, and its low εHf= -6 and εNd= -3, at 3300 Ma. SHC granites were emplaced throughout the Archean, from 3800 to 2700 Ma, but are predominant in the Neoarchean. They appear to have been mainly formed from the reworking of the SHC TTG, as supported by their low εHf and εNd initial values of respectively -16 and -11 at 2700 Ma. The granitoids include numerous enclaves of supracrustal rocks from various size, up to a few kilometers in scale, consisting of metavolcanic metasedimentary rocks. Previous work has suggested that they were formed at two different ages, with the younger Upernavik supracrustal unit deposited around 3400 Ma and the older Nulliak supracrustal assemblage deposited at around 3750 Ma. We show that both units are comparatively geochemically homogeneous with no distinction between the mafic and ultramafic rocks from both supracrustal assemblages. They mainly consist of mafic metavolcanic amphibolites with tholeiitic affinities, consistent with more depleted mafic and more enriched compositions produced by magmatic differentiation. Their complementary Eu anomaly and whole-rock geochemistry suggest that they formed from fractional crystallization of gabbroic assemblage that derived from similar if not the same parental magma. The mafic metavolcanic rocks are also often associated with ultramafic rocks that we divided into two distinct units, respectively referred as the high-Fe and the low-Fe ultramafic rocks, characterized by different FeO contents and Al/Ti ratio. They both represent olivine-rich cumulative rocks derived from distinct parental komatiitic basalt magmas. Our interpretation contrasts with previous work suggesting that the SHC ultramafic rocks were komatiites and slivers of residual lithospheric mantle. Most SHC TTG exhibit a positive 142Nd anomaly, as high as µ142Nd = +15, suggesting a source formed by differentiation in the Hadean. This 142Nd isotopic composition is similar to the Nulliak supracrustal rocks that exhibit on average a µ142Nd of +10. TTG is generally considered to derive from a mafic precursor. This study therefore shows that mafic crustal source of the SHC Eoarchean TTG, potentially the Nulliak metabasalts, derives from an ancient highly depleted mantle, described as the Saglek mantle, sharing a similar early history as the mantle reservoir involved in the formation of the ancient Itsaq terrane of southwest Greenland. The Saglek depleted mantle is interpreted to have formed at ~4400 Ma, exhibit highly depleted signature with a 147Sm/144Nd ratio of 0.221-0.240.

Herbivorous coral reef fishes play an important role in helping to structure their environment directly by consuming algae and indirectly by promoting coral health and growth. These fishes are generally separated into three broad groups: browsers, grazers, and excavators/scrapers, with these groupings often thought to have a fixed general function and all fishes within a group thought to have similar ecological roles. This categorization assumes a high level of functional redundancy within herbivorous fishes. However, recent evidence questions the use of this broad classification scheme, and posits that there may actually be more resource partitioning within these functional groupings. Here, I use a compound-specific stable isotope approach (CSIA) to show there appears to be a greater diversity of functional roles than previously assumed within broad functional groups. The δ13C signatures from essential amino acids of reef end-members (coral, macroalgae, detritus, and phytoplankton) and fish muscle were analyzed to investigate differences in resource use between fishes. Most end-members displayed clear isotopic differences, and most fishes within functional groups were dissimilar in their isotopic signature, implying differences in the resources they target. No grazers closely resembled each other isotopically, implying a much lower level of functional redundancy within this group; scraping parrotfish were also distinct from excavating parrotfish and to a lesser degree distinct between scrapers. This study highlights the potential of CSIA to help distinguish fine-scale ecological differences within other groups of reef organisms as well. These results question the utility of lumping nominally herbivorous fishes into broad groups with assumed similar roles. Given the apparent functional differences between nominally herbivorous reef fishes, it is important for managers to incorporate the diversity of functional roles these fish play.