京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第20460号 / 人博第810号 / 新制||人||194(附属図書館) / 28||人博||810(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 田部 勢津久, 教授 加藤 立久, 教授 吉田 寿雄 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

No description available.

The Cardigan pluton, located in the southern half of New Hampshire, is a strongly peraluminous, S-type granite which is granodioritic in composition. It is inferred to have been emplaced rapidly, thrust up along west-verging nappes during the Acadian orogeny. Distinctive pods, consisting of 50 to 70 percent modal garnet, are found throughout the pluton in assemblages of garnet + sillimanite + biotite + plagioclase + quartz. These garnetite rocks present an intriguing case for restite. Textural features of the garnetite rocks, such as fibrolitic sillimanite mats and flat, unzoned major and trace-element garnet grain profiles, provide evidence for biotite dehydration melting with single-stage garnet growth from the reaction: bio + plag + qtz + kspar = gar + sill + liq. Temperatures calculated using garnet-biotite (GB) thermometry and garnet-aluminum silicate-quartz-plagioclase (GASP) barometry yield estimates between 662-714ºC and 3.8 kbars. These low calculated temperatures are most likely the result of biotite compositions which have been altered by retrograde exchange reactions. The dominant source rock for the Cardigan magmas was likely calc-pelitic to greywacke in composition. Major element modeling suggests that ~70% melting of a calc-pelitic metasediment from the Central Maine trough could have generated a granodioritic melt similar to the average granodiorite of the Cardigan pluton. However, most of the Cardigan garnetite rocks appear to have been derived from pelites, as they are too poor in CaO and Na2O. Hence, though the majority of garnetite rocks cannot represent the dominant restite of the source rocks that produced the Cardigan pluton, they do appear to be the melt-depleted residue of an unidentified pelitic source. Comparison of Nd and Sr isotopic data from garnetite and Central Maine trough metasediments permit an interpretation that the Lower Rangeley Formation, from the Central Maine trough, could be the source rock of the Cardigan magmas. However, one feldspar Pb isotopic analysis in the literature (Moench and Allienikoff, 2002) and rare monazite chemical ages near 600 Ma suggest that the Cardigan pluton does not have a Laurentian source (i.e. Lower Rangeley Formation or other Central Maine trough metasediments), whereas an inferred peri-Gondwanan basement source is permissible.

Thesis advisor: Ethan Baxter / Thesis advisor: Mark Behn / Subduction zones are areas of significant mass transfer between Earth’s crust and mantle. The dehydration of water-rich minerals such as serpentinite and lawsonite introduces water and volatiles into the subduction interface, that then travel to the mantle wedge above. The chemical composition, speciation, and redox effect of these fluids carry important implications for arc volcanism and the mobility of economically significant elements. This study uses Fe and Zn isotopic variation in eclogite-breccias from the Monviso ophiolite, combined with Sm-Nd garnet geochronology, to study the composition and redox effects of fluids that were produced during eclogite and blueschist facies metamorphism, and the timescales over which the brecciation and fluid flux events happened. Fe and Zn isotopic measurements were made on a series of four breccia matrix generations (M1-M4), generated during the progressive brecciation of the original Fe-Ti gabbros and the influx of both internally and externally derived fluids. The ∂56Fe and ∂66Zn data display a bi-modal distribution, with early matrix crystallization (M1-3) imparting progressively lighter ∂66Zn values while the ∂56Fe remains relatively unchanged. The last stage of metasomatic rind formation (M4) is associated with a decrease in both Fe and Zn isotopic values and a particularly significant shift in the Fe isotopes. This distribution suggests that early brecciation (M1-3) resulted from small-scale internal fluid flow that did not have a measurable effect on the isotopic composition and redox state of the system. By contrast, late metasomatic rind formation (M4) was facilitated by the flow of large amounts of external fluids with a strongly negative Fe and Zn isotope signature that affected the redox state of the mafic slab and may be responsible for transferring oxidized material into the mantle wedge. Dating of the M4 matrix generation yielded an age of 41.31± 0.60 Ma. A compilation of age data from Monviso suggests peak metamorphism and initial brecciation (M1 formation) likely occurred at ~45 Ma, the formation of the M4 matrix representing the end of eclogite-facies retrogression and brecciation at ~41 Ma, and final blueschist and greenschist retrogression at ~38-35Ma, yielding timescale of ~4Ma for the entire history of brecciation and fluid flux associated with the Monviso eclogite breccias. / Thesis (MS) — Boston College, 2022. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

A petrographic study has been made of the contact relations between metagabbro and nepheline gneiss underlain by marble, in Monmouth township, Haliburton County, Ontario. A bad of hornblende nepheline-garnet gneiss about 80 feetwide trending north-south is underlain at a shear contact by marble. Round inclusion up to 18 inches across of red pyroxene with some spinel and rimmed by olivine occur in the marble a few feet below the contact. For a few inches above the contact the nepheline gneiss sometimes is biotite-bearing. To the east the nepheline gneiss grades into a band of hybrid nepheline metagabbro (containing pink augite) about 50 feet wide. This in turn is followed by a zone of garnetiferous clinozoisite metagabbro about 220 feet wide. Clinozoisite persists in the metagabbro for 100 feet beyond this zone and is followed by hornblende-(pyroxene)-plagioclase metagabbro. Pyroxene-garnet-(nepheline) skarn is interlayered with nepheline gneiss at one outcrop ear the fault contact with marble. It appears that gabbroic magma has intruded limestone and developed a skarn at the contact. Assimilation of lime by the magma has developed pink augite (titanaugite ?) , clinozoisite and grossularite in the gabbro. Subsequent injection of a highly fluid nepheline magma, or of solutions containing soda, alumina and iron and not saturated with silica, formed nepheline-bearing rock between marble and gabbro. Soda metasomatism produced a hybrid nepheline gabbro adjacent to the nepheline-bearirg rock. Regional metamorphism later imparted a foliation to the marble and nepheline rock, and produced a metamorphic texture the gabbro. Faulting of a unknown age brought nepheline gneiss and marble into sharp contact and probably trapped the skarn as horses only one of which is now exposed. / Thesis / Doctor of Philosophy (PhD)

A short history of micrometric analyses of rocks; the use of the point counter to determine the effect of orientation on the bulk composition of metamorphic rocks, the variations and limitations of the method with comparison of calculated analyses from the modes with an ordinary chemical analysis. The discrepancies lie within the range of experimental error. A quantitative interpretation by the use of statistics is offered. / Thesis / Master of Science (MSc)

This article belongs to the Proceedings of The 37th International Symposium on Dynamical Properties of Solids.

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No description available.

Travel times from a refraction and wide-angle reflection seismic survey across the Coast Plutonic Complex and Stikine terrane of British Columbia were inverted to derive two dimensional P and S-wave seismic velocity models of the crust and uppermost mantle. A felsic upper crust and a felsic to intermediate middle crust are observed in both the batholith complex and the accreted Stikine island arc terrane. The P and S wave models demonstrate a high-velocity (P 7.0 km/s, S 3.8 km/s) layer in the lower crust beneath the youngest (late Cretaceous to Eocene) portion of the continental arc complex. In contrast, the lower crust under the Stikine terrane has lower velocities consistent with amphibolite or other hydrated mafic rocks. The Moho is at ~35 km depth under the Stikine terrane, deepens to ~38 km beneath the youngest portion of the arc, then shallows towards the coast. The high velocity zone under the younger portion of the Coast Plutonic Complex has a 1.81 Vp/Vs ratio and is interpreted to have a bulk composition of mafic garnet granulite. This garnet granulite and large volumes of granodiorite-dominated melt were created by arc dehydration melting of amphibolite (or hydrated gabbro) in the pre-existing lower crust Reverse time migration method was applied to image aftershocks recorded by a dense array deployed after the 2011 Virginia earthquake. Events as tiny as magnitude -2 were successfully imaged as point sources. The propagation of energy release as a function of time and space was observed for events larger than magnitude 2.5. Spatial resolution of the images was ~200 m, which synthetic data tests show was primarily limited by the temporal sampling rate. Improved temporal and spatial sampling could produce images with sharper resolution. / Ph. D.