Metamorphic Pressure Temperature Time Paths

Fiordland, New Zealand offers an opportunity to study exposures of mid- to- lower crust that contain evidence for high temperature and pressure processes occurring beneath magmatic arcs. This thesis presents pressure, temperature, and time paths for rocks along Milford Sound to better understand the tectonic history and timing of metamorphism within and adjacent to the Anita Shear Zone. Samples analyzed are from St. Anne Point to near Milford Village here named the Milford Sound Transect. Rocks from the Thurso Gneiss (18MSNZ510a), Milford Geiss (15NZ51), Pembroke Granulite (05NZ12), and Camp Oven Creek Paragneiss (15NZ63), from west to east along the Milford Transect yielded garnet Sm-Nd ages of 99℗ł7, 93℗ł5, 122℗ł2, and 119℗ł8 Ma. Mineral assemblage diagrams and thermobarometry indicate somewhat higher pressures and temperatures in the central and eastern parts of the Milford Transect. Rocks in the Anita Shear Zone (18MSNZ511b; 18MSNZ510a) equilibrated at 9.5 to 11 kbar at temperatures of 650-700 ℗ʻC and 525 0́3 625 ℗ʻC, respectively. East of the Anita Shear Zone (15NZ51) peak metamorphism reached 10.5 to 11 kbar at 625-675 ℗ʻC. These new P-T-t data, with P-T data from Czertowicz and others (2016) and Klepeis and others (1999) provide a direct temporal link between garnet growth, high pressure metamorphism, and shear zone fabrics. Further east, samples 05NZ12, and 15NZ63 equilibrated at; 11-16 kbar at 640 0́3 725 ℗ʻC; and 8.5-13.5 kbar at 525- 625 ℗ʻC, respectively. Our new data delineates a ~ 7 km wide zone of 100 Ma 9.5 to 11 kbar metamorphism along the western, and a ~8 km wide zone of 11 kbar >100 Ma metamorphism along the eastern part of the Milford Transect. Garnet age differences between 15NZ51 and 05NZ12 of ca. 30 m.y., higher pressures of 11-16 kbar for 05NZ12, and the ~ 4 km distance between them is compatible with possible fault separation. I infer a fault or shear zone separating the young (100 Ma) medium pressure (9.5 to 11 kbar) metamorphism along the eastern Milford Transect and the considerably older (122 to 126 Ma) Pembroke Granulite metamorphism at higher pressure (11 kbar).

Petrochronology is a rapidly emerging branch of Earth science that links time (ages or rates) with specific rock-forming processes and their physical conditions. It is founded in petrology and geochemistry, which define a petrogenetic context or delimit a specific process, to which chronometric data are then linked. This combination informs Earth’s petrogenetic processes better than petrology or geochronology alone. This volume and the accompanying short courses address three broad categories of inquiry. Conceptual approaches chapters include petrologic modeling of multi-component chemical and mineralogic systems, and development of methods that include diffusive alteration of mineral chemistry. Methods chapters address four main analytical techniques, specifically EPMA, LA-ICP-MS, SIMS and TIMS. Mineral-specific chapters explore applications to a wide range of minerals, including zircon (metamorphic, igneous, and detrital/Hadean), baddeleyite, REE minerals (monazite, allanite, xenotime and apatite), titanite, rutile, garnet, and major igneous minerals (olivine, plagioclase and pyroxenes). These applications mainly focus on metamorphic, igneous, or tectonic processes, but additionally elucidate fundamental transdisciplinary progress in addressing mechanisms of crystal growth, the chemical consequences of mineral growth kinetics, and how chemical transport and deformation affect chemically complex mineral composites. Most chapters further recommend areas of future research.

Although it is known that what ultimately drives metamorphism is heat, what is less certain is the distribution of heat within the crust and the rates of heat flux through crustal rocks. This text explores the factors that control metamorphism and the rates of metamorphic processes.

Metamorphic rocks are one of the three classes of rocks. Seen on a global scale they constitute the dominant material of the Earth. The understanding of the petrogenesis and significance of metamorphic of geological education. rocks is, therefore, a fundamental topic There are, of course, many different possible ways to lecture on this theme. This book addresses rock metamorphism from a relatively pragmatic view point. It has been written for the senior undergrad uate or graduate student who needs practical knowledge of how to interpret various groups of minerals found in metamorphic rocks. The book is also of interest for the non-specialist and non-petrolo gist professional who is interested in learning more about the geolo gical messages that metamorphic mineral assemblages are sending, as well as pressure and temperature conditions of formation. The book is organized into two parts. The first part introduces the different types of metamorphism, defines some names, terms and graphs used to describe metamorphic rocks, and discusses principal aspects of metamorphic processes. Part I introduces the causes of metamorphism on various scales in time and space, and some principles of chemical reactions in rocks that accompany metamorphism, but without treating these principles in detail, and presenting the thermodynamic basis for quantitative analysis of reactions and their equilibria in metamorphism. Part I also presents concepts of metamorphic grade or intensity of metamorphism, such as the metamorphic-facies concept.

This user-friendly reference for students and researchers presents the basic mathematical theory, before introducing modelling of key geodynamic processes.