Evolution of microstructures and fluid inclusions of naturally deformed peridotites: Implications for physico-chemical heterogeneity in the upper mantle
자연 상에서 변형된 감람암의 미세구조와 유체포유물의 진화사: 상부맨틀의 물리화학적 불균질성에 관한 의의

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dc.description학위논문 (박사)-- 서울대학교 대학원 : 지구환경과학부, 2017. 2. 정해명.-
dc.description.abstractThe Earths uppermost layer, the lithosphere, consists of the crust and upper mantle, in particular, the lithospheric mantle is the space that physically and chemically forms the roots of crust. Mantle-derived peridotites can provide important information about the physico-chemical properties of the upper mantle (i.e., mantle metasomatisms and deformation processes), thus, it plays an important role in understanding Earth's geochemical and rheological evolutionary processes.

In this dissertation, naturally deformed peridotites (xenolith and massif type) were studied using various analytical instruments (SEM-EBSD, EPMA, FTIR-Raman spectroscopy, FIB, Heating-Cooling stage, etc.) in order to understand how deformation microstructures and fluid inclusions were evolved from Rio Grande Rift (New Mexico, USA) and Yugu area (Gyeonggi Massif, Korea).

Five spinel peridotite xenoliths, hosted in alkali basalts, were collected from Adams Diggings in the western margin of the Rio Grande Rift (RGR), New Mexico, USA. Based on fluid inclusion petrography, two distinct generations of fluid inclusion assemblages, both hosted by orthopyroxenes, namely Type-1 (earlier) and Type-2 (later) FIs, were identified. Results from fluid inclusion petrography together with various analytical results indicated that the timing of the entrapment and the composition of the trapped fluid were different between the Type-1 and Type-2 FIs. All of these results indicate that there were at least two fluid invasions with different fluid compositions at different pressures (depth) beneath the RGR mantle. The earlier fluid invasion (C–O–N–S) happened before or during formation of exsolution lamellae and was trapped as Type-1 FI in the cores of orthopyroxenes whereas the later fluid invasion (C–O–H–S) was trapped as Type-2 FI after the formation of the orthopyroxene porphyroclasts with exsolution lamellae. The two fluid invasions in the Adams Diggings peridotites indicate the complexity of mantle fluids around the RGR.

Transitional characteristics of microstructures and olivine fabrics developed in a mantle shear zone from the Yugu peridotite body (Gyeonggi Massif, Korea) were studied. The Yugu peridotite body predominantly comprises spinel harzburgite together with minor lherzolite, dunite, and clinopyroxenite. Based on microstructural characteristics of highly deformed peridotites, we classified into proto-mylonite, proto-mylonite to mylonite transition, mylonite, and ultra-mylonite. Olivine fabrics changed from A-type (proto-mylonite) via D-type (mylonite) to E-type (ultra- mylonite). Olivine fabric transition is interpreted as occurring under hydrous conditions at low temperature and high strain, because of characteristics such as Ti- clinohumite defects (and serpentine) and fluid inclusion trails in olivine, and a hydrous mineral (pargasite) in the matrix, especially in the ultra-mylonitic peridotites.
dc.description.tableofcontentsCHAPTER I. Introduction 1
CHAPTER II. Fluid invasions in the lithospheric upper mantle based on fluid inclusion study in spinel peridotites from Adams Diggings, Rio Grande Rift, U.S.A. 5
Abstract 5
2.1. Introduction 7
2.2. Geology and sampling 9
2.3. Analytical techniques 16
2.4. Fluid inclusion petrography 18
2.5. Microthermometry 20
2.6. Raman microspectrometry 21
2.6.1. Type-1 FIs 21
2.6.2. Type-2 FIs 22
2.7. Focused ion beamscanning electron microscopy 28
2.8. Discussion 32
2.8.1. Entrapment of fluid inclusions 32
2.8.2. Temperature estimate for fluid inclusion entrapment 33
2.8.3. Type-1 FIs 38
2.8.4. Type-2 FIs 39
2.8.5. Possible source of the fluids related to metasomatic evolution in the Adams Diggings 40
2.8.6. Post-entrapment reaction processes within inclusions 45
2.9. Conclusions 49
CHAPTER III. Microstructural evolution of the Yugu peridotites in the Gyeonggi Massif, Korea: Implications for olivine fabric transition in mantle shear zones
Abstract 50
3.1. Introduction 52
3.2. Geologic setting 54
3.3. Field observations and sampling 57
3.4. Microstructures 60
3.5. Dislocation microstructures 66
3.6. Lattice preferred orientation and fabric strength of olivine 69
3.7. Olivine grain size and paleopiezometry 73
3.8. Fourier transform infrared spectroscopy 74
3.9. Mineral chemistry 78
3.10. Thermometry 82
3.11. Discussion 83
3.11.1 Olivine fabric transition in the mantle shear zone 83
3.11.2 Mechanism of olivine deformation in the mantle shear zone 87
3.12. Conclusions 89
CHAPTER IV. Conclusions 91
dc.format.extent8541871 bytes-
dc.publisher서울대학교 대학원-
dc.subjectfluid inclusion-
dc.subjectmantle metasomatism-
dc.subjectmantle evolution-
dc.subjectmantle heterogeneity-
dc.titleEvolution of microstructures and fluid inclusions of naturally deformed peridotites: Implications for physico-chemical heterogeneity in the upper mantle-
dc.title.alternative자연 상에서 변형된 감람암의 미세구조와 유체포유물의 진화사: 상부맨틀의 물리화학적 불균질성에 관한 의의-
dc.contributor.AlternativeAuthorPark, Munjae-
dc.citation.pagesiv, 120-
dc.contributor.affiliation자연과학대학 지구환경과학부-
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College of Natural Sciences (자연과학대학)Dept. of Earth and Environmental Sciences (지구환경과학부)Theses (Ph.D. / Sc.D._지구환경과학부)
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