Metamorphic Structures and Textures 2020 M.Sc
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Open Geosci. 2015; 7:53–64 Research Article Open Access László Molnár*, Balázs Vásárhelyi, Tivadar M. Tóth, and Félix Schubert Integrated petrographic – rock mechanic borecore study from the metamorphic basement of the Pannonian Basin, Hungary Abstract: The integrated evaluation of borecores from the 1 Introduction Mezősas-Furta fractured metamorphic hydrocarbon reser- voir suggests significantly distinct microstructural and Brittle fault zones of crystalline rock masses can serve as rock mechanical features within the analysed fault rock migration pathways or also as sealing surfaces for fluid samples. The statistical evaluation of the clast geometries flow in the Earth’s crust, so the understanding of their in- revealed the dominantly cataclastic nature of the sam- ternal structure is crucial for interpreting hydraulic sys- ples. Damage zone of the fault can be characterised by tems. Earlier studies [1, 2] on the architecture of fault an extremely brittle nature and low uniaxial compressive zones defined two main structural elements: first, a weakly strength, coupled with a predominately coarse fault brec- disaggregated, densely fractured “damage zone” and a cia composition. In contrast, the microstructural manner strongly deformed and fragmented “fault core”, where of the increasing deformation coupled with higher uni- the pre-existing rock fabrics were erased by fault devel- axial compressive strength, strain-hardening nature and opment. These elements can be characterised by the for- low brittleness indicate a transitional interval between mation of diverse tectonite types (fault breccias, catacla- the weakly fragmented damage zone and strongly grinded sites, fault gouges), which often also possess quite hetero- fault core. Moreover, these attributes suggest this unit is geneous rheological features. -
Metamorphic Rocks.Pdf
Metamorphism & Metamorphic Rocks (((adapted from Brunkel, 2012) Metamorphic Rocks . Changed rocks- with heat and pressure . But not melted . Change in the solid state . Textural changes (always) . Mineralogy changes (usually) Metamorphism . The mineral changes that transform a parent rock to into a new metamorphic rock by exposure to heat, stress, and fluids unlike those in which the parent rock formed. granite gneiss Geothermal gradient Types of Metamorphism . Contact metamorphism – – Happens in wall rock next to intrusions – HEAT is main metamorphic agent . Contact metamorphism Contact Metamorphism . Local- Usually a zone only a few meters wide . Heat from plutons intruded into “cooler” country rock . Usually forms nonfoliated rocks Types of Metamorphism . Hydrothermal metamorphism – – Happens along fracture conduits – HOT FLUIDS are main metamorphic agent Types of Metamorphism . Regional metamorphism – – Happens during mountain building – Most significant type – STRESS associated with plate convergence & – HEAT associated with burial (geothermal gradient) are main metamorphic agents . Contact metamorphism . Hydrothermal metamorphism . Regional metamorphism . Wide range of pressure and temperature conditions across a large area regional hot springs hydrothermal contact . Regional metamorphism Other types of Metamorphism . Burial . Fault zones . Impact metamorphism Tektites Metamorphism and Plate Tectonics . Fault zone metamorphism . Mélange- chaotic mixture of materials that have been crumpled together Stress (pressure) . From burial -
The Initiation and Development of Metamorphic Foliation in the Otago Schist, Part 2: Evidence from Quartz Grain-Shape Data
The initiation and development of metamorphic foliation in the Otago Schist, Part 2: Evidence from quartz grain-shape data AARON STALLARD,1 DAVID SHELLEY1 AND STEVE REDDY2 1Department of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand ([email protected]) 2Tectonics Special Research Centre, Dept. of Applied Geology, Curtin University of Technology, Perth, WA 6845, Australia ABSTRACT Shape, size and orientation measurements of quartz grains sampled along two transects that cross zones of increasing metamorphic grade in the Otago Schist, New Zealand, reveal the role of quartz in the progressive development of metamorphic foliation. Sedimentary compaction and diagenesis contributed little to forming a shape preferred orientation (SPO) within the analysed samples. Metamorphic foliation was initiated at sub-greenschist facies conditions as part of a composite S1- bedding structure parallel to the axial planes of tight to isoclinal F1 folds. An important component of this foliation is a pronounced quartz SPO that formed dominantly by the effect of dissolution- precipitation creep on detrital grains in association with F1 strain. With increasing grade, the following trends are evident from the SPO data: (i) a progressive increase in the aspect ratio of grains in sections parallel to lineation, and the development of blade-shaped grains; (ii) the early development of a strong shape preferred orientation so that blade lengths define the linear aspect of the foliation (lineation) and the intermediate axes of the blades define a partial girdle about the lineation; (iii) a slight thinning and reduction in volume of grains in the one transect; (iv) an actual increase in thickness and volume in the survivor grains of the second transect. -
Metamorphic Fabrics
11/30/2015 Geol341 J. Toro Topics • Fabrics • Foliation, cleavage, lineation Metamorphic Rocks and – Cleavage and Folds –Geometry Cleavage Development – Strain significance • Origin of Cleavage – Pressure solution – Passive rotation – Recrystallization • Shear zones Many diagrams are from Earth Structure, van der Pluijm and Marshak, 2004 2013 Geothermal Gradient and Metamorphism Naming of Metamorphic Rocks Slatey cleavage Gneiss Segregation of mafic and felsic components Where does it come from? 1 11/30/2015 Looks like bedding, but is it? Metamorphic layering Brooks Range, AK Quartz-mica schist Isoclinal Fold Transposition of Layering Fabric “Arrangement of component features in a rock” van der Pluijm & Marshak •Includes: •Texture •Composition •Microstructure •Preferred Orientation Horizontal fabric => Vertical fabric 2 11/30/2015 Quartz-mica schist Fabric Elements •Bedding (S0) •Compositional layering •Crystallographic orientation •Fold Hinges •Cleavage planes (S1) •Mineral elongation lineation Passchier and Trouw (1996) Metamorphic Fabrics Metamorphic Fabrics • Foliation : Cleavage, Schistosity • Foliation • Lineation: Mineral Lineation, Intersection Lineation – Cleavage – Schistosity • Lineation Random fabric S-tectonite L-tectonite L/S-tectonite Foliation Lineation S-Tectonites L-Tectonites Schists Columbia Pluton, VA Lineated Gneiss USGS photo U. Western Ontario photo 3 11/30/2015 L-S Tectonites 3D Strain - Flinn diagram No strain along 3rd dimension Cigars S =S >S S1/S2 1 2 3 S1>S2=S3 Lineated and foliated gneiss, Himalayas Prolate -
Fabric Foliation
2/14/15 Fabric • The characteristics of the geometry and spacing of the elements that make up a rock. – Linear – Planar – Random Foliation • Any fabric-forming planar or curvi-planar structure. • May be primary or tectonic • Many rocks have more than one foliation • Approximate as planes and/or surfaces 1 2/14/15 Cleavage • Describes the tendency of a rock to split along foliation planes • Not the same as cleavage of a single crystal/mineral ! Where well-developed, synonym for foliation. Lineation • Linear elements in a rock • One axis >> other two • Penetrative, surface or geometric Image from your friend Wikipedia 2 2/14/15 Keep thinking about strain ellipse • Foliations form perpendicular to shortening (e3 axis is pole to foliation plane) • Lineations – Elongation – mineral stretching = e1 – Shear lineations – oblique to strain ellipse axes, gives asymmetry/rotation 3 2/14/15 Tectonites • Fabrics in deformed metamorphic rocks are referred to as tectonites L-tectonite 4 2/14/15 S-tectonite Gneissic banding • Gneiss – Early layering is folded – Flattened limbs are parallel • Transposed foliation 5 2/14/15 Mylonites • Contain a “mylonitic foliation” formed by crystal plastic deformation in a shear zone (pure or simple) • Transposed layering • Shear zone fault rocks Describing cleavage 6 2/14/15 Metamorphosis of a pelite • Slaty cleavage – Preferential dissolution of some minerals – Perpendicular to shortening • Minerals line up • Becomes more continuous as it 1mm develops Crenulation = 2nd foliation folds first 7 2/14/15 Crenulation Cleavage -
Magmatic and Tectonic Continuous Casting in the Circum-Pacific Region Jon E
Arizona Geological Society Digest 22 2008 Magmatic and tectonic continuous casting in the circum-Pacific region Jon E. Spencer Arizona Geological Survey, 416 W. Congress St., #100, Tucson, Arizona, 85701, USA Yasuhiko Ohara Hydrographic and Oceanographic Department of Japan, Tokyo, 104-0045, Japan, and Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Kanagawa 237-0061, Japan ABSTRACT Continuous casting is an industrial process for producing metal in continuous linear form. Cooling of the cast medium occurs across a slip surface in this process. The same process was active in geologic settings in which lava extrusion was accompanied by formation of striations on the surface of the extrusion. Such grooves resulted from irregularities on colder and harder rock that formed the confining orifice from which the grooved lava was extruded. In a variant of this process, lavas that emerged from beneath deep-sea lava-lake crusts were striated on their upper surfaces as they emerged. In the case of the grooved extrusion at Sacsayhuamán, Perú, lateral displacement of rock overlying a very shallow intrusion may have caused striations to form on the underlying intrusion as it was exhumed. Deep-sea metamorphic core complexes are known primarily by their corrugated upper sur- faces as identified with multibeam sonar. Recovered samples, including from drilling, typically include gabbro and basalt, indicating that magmatism was a major process in construction of the corrugated normal-fault footwall. The 125-km-long Godzilla Mullion in the Parece Vela Basin of the Philippine Sea, which is the largest known metamorphic core complex on Earth, includes a single antiformal groove 60 km long and 5 km wide. -
Kinematic and Tectonic Significance of Microstructures And
Transactions of the Royal Society of Edinburgh: Earth Sciences, 77, 99-125. 1986 Kinematic and tectonic significance of microstructures and crystallographic fabrics within quartz mylonites from the Assynt and Eriboll regions of the Moine thrust zone, NW Scotland R. D. Law, M. Casey and R. J. Knipe ABSTRACT: Using a combination of optical microscopy and X-ray texture goniometry, an integrated microstructural and crystallographic fabric study has been made of quartz mylonites from thrust sheets located beneath, but immediately adjacent to, the Moine thrust in the Assynt and Eriboll regions of NW Scotland. A correlation is established between shape fabric symmetry and pattern of crystallographic preferred orientation, a particularly clear relationship being observed between shape fabric variation and quartz a-axis fabrics. Coaxial strain paths dominate the internal parts of the thrust sheets and are indicated by quartz c- and a-axis fabrics which are symmetrical with respect to foliation and lineation. Non-coaxial strain paths are indicated within the more intensely deformed quartzites located near the boundaries of the sheets by asymmetrical c- and c-axis fabrics. These kinematic interpretations are supported by microstructural studies. At the Stack of Glencoul in the northern part of the Assynt region, the transition zone between these kinematic (strain path) domains is located at approximately 20 cm beneath the Moine thrust and is marked by a progression from symmetrical cross-girdle c-axis fabrics (30cm beneath the thrust), through asymmetrical cross-girdle c-axis fabrics to asymmetrical single girdle c-axis fabrics (0-5 cm beneath the thrust). Tectonic models (incorporating processes such as extensional flow, gravity spreading and tectonic loading) which may account for the presence of strain path domains within the thrust sheets are considered, and their compatibility with local thrust sheet geometries assessed. -
Lab 5: Textures and Identification of Metamorphic Rocks
LAB 5: TEXTURES AND IDENTIFICATION OF METAMORPHIC ROCKS OBJECTIVES: 1) to become familiar with textures characteristic of metamorphic rocks; 2) to become familiar with properties important in recognizing and classifying metamorphic rocks; 3) to become familiar with the mineralogy of common metamorphic rocks. INTRODUCTION: Metamorphic rocks are formed from pre-existing rocks by recrystallization in the solid state under the effects of heat, pressure, shearing (grinding), or replacement by materials (ions) dissolved in water. They are classified on the basis of texture (foliated vs. non-foliated), grain-size, and mineral composition. Texture: Metamorphic rocks may have either foliated (layered) or non-foliated texture. Foliated texture is a pervasive layering caused by compositional layering or by the parallel orientation of platy (e.g, mica) or elongate (e.g., amphibole) mineral grains. Foliation is caused by recrystallization under directed (compressional) stress. However, if the rock lacks platy or elongate minerals, it will not develop foliation even though it recrystallized under very great pressure (examples are marble and quartzite). Grain size: Grain size reflects pressure and temperature conditions of metamorphism. Generally, higher temperatures and pressures (higher grades of metamorphism) favor larger grains, and lower temperatures and pressures favor smaller grains. Mineral composition: Mineral composition reflects the composition of the parent rock and the pressure and temperature conditions under which the metamorphism occurred. See Marshak p. 241-244 for discussion of metamorphic grades and for the index minerals used to identify them. Classification: Foliated metamorphic rocks: Grain size is the main basis for classification of foliated metamorphic rocks. Slates are very fine-grained, well-foliated (very well-layered) rocks. -
Mineralogical Evidence for Partial Melting and Melt-Rock Interaction Processes in the Mantle Peridotites of Edessa Ophiolite (North Greece)
minerals Article Mineralogical Evidence for Partial Melting and Melt-Rock Interaction Processes in the Mantle Peridotites of Edessa Ophiolite (North Greece) Aikaterini Rogkala 1,* , Petros Petrounias 1 , Basilios Tsikouras 2 , Panagiota P. Giannakopoulou 1 and Konstantin Hatzipanagiotou 1 1 Section of Earth Materials, Department of Geology, University of Patras, 265 04 Patras, Greece; [email protected] (P.P.); [email protected] (P.P.G.); [email protected] (K.H.) 2 Physical and Geological Sciences, Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong BE1410, Bandar Seri Begawan, Brunei Darussalam; [email protected] * Correspondence: [email protected]; Tel.: +30-2610996288 Received: 10 December 2018; Accepted: 14 February 2019; Published: 17 February 2019 Abstract: The Edessa ophiolite complex of northern Greece consists of remnants of oceanic lithosphere emplaced during the Upper Jurassic-Lower Cretaceous onto the Palaeozoic-Mesozoic continental margin of Eurasia. This study presents new data on mineral compositions of mantle peridotites from this ophiolite, especially serpentinised harzburgite and minor lherzolite. Lherzolite formed by low to moderate degrees of partial melting and subsequent melt-rock reaction in an oceanic spreading setting. On the other hand, refractory harzburgite formed by high degrees of partial melting in a supra-subduction zone (SSZ) setting. These SSZ mantle peridotites contain Cr-rich spinel residual after partial melting of more fertile (abyssal) lherzolite with Al-rich spinel. Chromite with Cr# > 60 in harzburgite resulted from chemical modification of residual Cr-spinel and, along with the presence of euhedral chromite, is indicative of late melt-peridotite interaction in the mantle wedge. Mineral compositions suggest that the Edessa oceanic mantle evolved from a typical mid-ocean ridge (MOR) oceanic basin to the mantle wedge of a SSZ. -
Review Our Ni 43-101 Technical Report Here
Titan Gold Property Form 43-101F1 Technical Report June 2020 TECHNICAL REPORT On the Titan Gold Property Klotz Lake Area, NTS Map 42F Thunder Bay Mining District Northwestern Ontario, Canada Prepared for: SOLDERA MINING CORP. 6th Floor 905 West Pender Street Vancouver, BC V6C 1L6 Prepared by: Martin Ethier, P.Geo. Consulting Geologist Hinterland Geoscience and Geomatics 620 Brewster Street. Haileybury, Ontario P0J 1K0 June 12, 2020 (Effective Date: June 12, 2020) 1 | P a g e Titan Gold Property Form 43-101F1 Technical Report June 2020 TABLE OF CONTENTS 1.0 SUMMARY ............................................................................................................... 6 2.0 INTRODUCTION ..................................................................................................... 10 2.1 Purpose of Report ............................................................................................. 10 2.2 Sources of Information ..................................................................................... 10 3.0 RELIANCE ON OTHER EXPERTS .............................................................................. 10 4.0 PROPERTY DESCRIPTION AND LOCATION ............................................................. 11 5.0 ACCESS, CLIMATE, PHYSIOGRAPHY, LOCAL RESOURCES, AND INFRASTRUCTURE 17 5.1 Access ................................................................................................................ 17 5.2 Climate ............................................................................................................. -
Squeezing Blood from a Stone: Inferences Into the Life and Depositional Environments of the Early Archaean
Squeezing Blood From A Stone: Inferences Into The Life and Depositional Environments Of The Early Archaean Jelte Harnmeijer A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Washington MMX Programs Authorized to Offer Degree: Center for Astrobiology & Early Earth Evolution and Department of Earth & Space Sciences Abstract A limited, fragmentary and altered sedimentary rock record has allowed few constraints to be placed on a possible Early Archaean biosphere, likewise on attendant environmental conditions. This study reports discoveries from three Early Archaean terrains that, taken together, suggest that a diverse biosphere was already well- established by at least ~3.5 Ga, with autotrophic carbon fixation posing the most likely explanation for slightly older 3.7 - 3.8 Ga graphite. Chapter 2 aims to give a brief overview of Early Archaean geology, with special reference to the Pilbara’s Pilgangoora Belt, and biogeochemical cycling, with special reference to banded-iron formation. Chapter 3 reports on the modelled behaviour of abiotic carbon in geological systems, where it is concluded that fractionations incurred through autotrophic biosynthesis are generally out of the reach of equilibrium processes in the crust. In Chapter 4, geological and geochemical arguments are used to identify a mixed provenance for a recently discovered 3.7 - 3.8 Ga graphite-bearing meta-turbidite succession from the Isua Supracrustal Belt in southwest Greenland. In Chapter 5 and 6, similar tools are used to examine a newly discovered 3.52 Ga kerogenous and variably dolomitized magnetite-calcite meta- sediment from the Coonterunah Subgroup at the base of the Pilbara Supergroup in northwest Australia. -
Geometry and Deformation History of Mylonitic Rocks and Silicified Zones Along the Mesozoic Connecticut Valley Border Fault, Western Massachusetts
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