petrology of ultramafic and related rocks along iraqi zagros thrust zone

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more rarely Zn, Mn, and Li; and Y represents ion of smaller size such as Cr, Al, Fe 3+ , Mg, Mn, Ti, V and even Fe 2+ ]. 1-1-1 Mode of occurrence of ultramafic rocks In the crust, ultramafic rocks are presented mainly in six major kinds. These are (1) layered igneous bodies, (2) zoned to irregularly shaped intrusion, (3) ultramafic lava flows (komatiites) and their differentiates, (4) kimberlite pipes and related intrusives, (5) Alpine type ultramafic rock bodies, and (6) nodules (including xenolith) in volcanic rocks. The major ultramafic bodies assigned to the one of two major groups, the layered and zoned to irregular bodies. Layered bodies include ophiolites. Zoned to irregularly shaped bodies include Alaska-type zoned complex and appinite-type ultramafic bodies. Each of these types has distinctive chemical, structural, and petrographic characteristics. These characteristics distinguish the individual type of ultramafic body, one from the other, as well as igneous bodies from metamorphic ultramafic rock bodies. The common metamorphic bodies of the crust are signed to the category of alpine-type ultramafic bodies, which are found commonly as irregular to elliptical bodies in mountain belts. The rocks in these bodies may have been formed initially as magmatic crystal cumulates, crystallized or recrystallized from mantle diapirs, and mantle tectonite. They are emplaced as mantle slab into the crust by faulting. Alpine-type ultramafic rocks in general have tectonic fabrics, and are characterized by olivines and orthopyroxenes with moderate to high Mg number. The rock bodies lack chilled margin and do not give circumference contact metamorphism. Perhaps more than other ultramafic bodies, alpine-type ultramafic rocks have severly undergone serpentinization. Alpine-type ultramafic rocks of crustal heritage may reveal the early histories of intrusion and crystallization, metamorphism, and deformation in the mountain belts as well as a synorogenic history, which also portrayed by the texture, structure, and minerals of the more common 3
ocks of the belt. These attributes provide an ample incentive for the study of alpine-type ultramafic rocks. 1-1-2 Genetic classification of ultramafic rocks 1-1-2-1 Cumulate ultramafics Cumulate ultramafics, typically dunites or pyroxenites, can form in layered intrusions as the bottommost “strata” of a fractionally crystallized melt (Winter, 2001). In a slowly cooling magma chamber, heavy crystallized minerals settle at the bottom of the chamber and accumulate much like sediment settling out of the water column in a pond. Because olivine is heavier and tends to crystallize at higher temperatures, it is more likely to fractionally crystallize out of a magma in the early stages of cooling, forming a layer of cumulate olivine crystals on the magma chamber floor (Winter, 2001). Some of the best examples of cumulate ultramafics in layered intrusions can be found in the ultramafic series of the Stillwater Complex in southwestern Montana. In these series, layers of olivine and chromian spinel are overlain by layers of olivine mixed with orthopyroxene, grading upward into orthoproxenite, and eventually into orthopyroxene and plagioclase (Winter, 2001). This succession of compositionally distinct layers grading upward from silica-poor minerals to silica-rich minerals represents a pattern in the cooling of mafic magmas which forms ostensibly stratified igneous plutons when exposed (Wyllie 1967, Winter, 2001, Buming et. al., 1997). 1-1-2-2 Tectonite ultramafics Mantle tectonite is a type of non-cumulate ultramafic rock often interpreted as an exposed fragment of primary or depleted mantle, which has been tectonically emplaced on the surface of the earth. These rocks are often associated with the basal layer of ophiolite; rocks interpreted as exposed sequence of oceanic plate emplaced on the surface of the Earth as a result of tectonic collision and thrust faulting (Winter, 2001). 4
Page 1 and 2: PETROLOGY OF ULTRAMAFIC AND RELATED
Page 3 and 4: We certify that we read this thesis
Page 5 and 6: ABSTRACT Four main ultramafic rock
Page 7 and 8: CONTENTS Chapter 1: Background, Aim
Page 9 and 10: Chapter 7: Conclusions and Recommen
Page 11 and 12: Figure 3 - 10: Field photograph of
Page 13 and 14: albite - tremolite zone, E = albite
Page 15 and 16: Figure 6 - 19: Time-paragenesis, al
Page 17 and 18: Table 6 - 2: Representative microna
Page 19: 1 BACKGROUND 1-1 Ultramafic rocks U
Page 23 and 24: 1-1-3 Metamorphism of ultramafics M
Page 25 and 26: Reaction 1: Isochemical serpentiniz
Page 27 and 28: 1-2-2 Jadeitites Jadeitite is compo
Page 29 and 30: In combining the new data on the se
Page 31 and 32: 2-1 Regional geology The Iraq Zagro
Page 33 and 34: 2-1-1 Geology of Penjwin area 2-1-1
Page 35 and 36: of Luta-Rash. Volcanic rocks are ex
Page 37 and 38: and a sandstone unit of the Paleoce
Page 39: Fig. 2-1: Tectonic subdivision of I
Page 42 and 43: Fig. 2-4: Field photograph of Gimo
Page 45 and 46: Chapter 3 Petrology of ultramafic r
Page 47 and 48: 3-1-2 Harzburgite Harzburgite is th
Page 49 and 50: 3-1-6 Serpentinite Two types of ser
Page 51 and 52: small amount of ilmenite. Hornblend
Page 53: In places, it is surrounded by fine
Page 62 and 63: 4 Mineralogy and mineral chemistry
Page 64 and 65: compositions with Mg-number ranging
Page 66 and 67: 4-3-4 Hydrous phases Hydrous phases
Page 68 and 69: Fig 4 -3: Compositions of chromian
Page 70 and 71:
Fig 4 -6: Compositions of chromian
Page 72 and 73:
Chapter 5 Discussions 55
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the tectonite region of the graph (
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involves loss and gain of CaO, SiO
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Fig. 5 - 1: Chromian spinel composi
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Fig. 5-3: Cr-number in spinel vs. F
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Chapter 6 Related rock 65
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plagioclase (Figs. 6 - 2 G,H) and z
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Plagioclase and ilmenite are the or
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2 CaAl 2 Si 2 O 8 (anorthite) + Na
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apatite grains, characterized by bl
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the rim. Estimated pressure - tempe
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16 clinozoisite + H 2 O. (16) From
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metamorphism. It was also formed du
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Fig. 6 - 2: Photomicrographs and im
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Fig. 6 - 4: Backscattered electron
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Fig. 6 - 7: Line scan profile acros
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Fig. 6 - 9: Line scan profile of pa
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Fig. 6 - 11: (A) Backscatter electr
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Fig. 6 - 13: Field of the approxima
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Fig. 6 - 15: Whole rock chemical co
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Fig. 6 - 17: Whole rock chemical co
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Fig. 6 - 19: Time-paragenesis, albi
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1 Conclusions 1. The Iraqi Zagros T
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2 Recommendations for further works
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Arai, S., 1987. An estimation of th
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Chakhmouradian, A.R., Reguir, E.P.,
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Evans, B.W., Frost, B.R., 1975. Chr
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Kamenetsky, V., Crawford, A. J., an
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Morand, V.J., 1990. High chromium a
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Watson, E.B., Wark, D. A. and Thoma
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Table 4 - 1: Representative microna
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Table 4 -11: Representative microna
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Table 4 -13: Representative microna
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Research public activity Peer-revie
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petrology of ultramafic and related rocks along iraqi zagros thrust zone

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