Announcements Draft #1 of fault paper due next Wed.! Late papers: lose 5% of grade per day.

Slides:



Advertisements
Similar presentations
Announcements Field trip to Tanque Verde this Saturday
Advertisements

Cleavage, foliation and lineation (Chapter 8 in Davis and Reynolds) Closely spaced planar to linear features that tend to be associated with folds, especially.
Metamorphic Rocks.
Structural Geology (Geol 305) Semester (071)
Chapter 17 Cleavage and Foliations. Cleavage ► Cleavage – A prominent planar structure that may differ in orientation from the bedding and indicate subsequent.
Metamorphic Rocks.
Metamorphic Rocks.
H.W. #3 + Read Solar Nebula Theory Study Guide for exam 2 Study Area for lab has practice exam All missed labs must be made up before lab exam All missed.
Metamorphism The transformation of rock by temperature and pressure Metamorphic rocks are produced by transformation of: Igneous, sedimentary and igneous.
Metamorphism: New Rocks from Old
Metamorphic Rocks. Metamorphic rocks Subjected to heat (and stress) Results in changes in the appearance –Mineralogical –Textural Any rock can be metamorphosed.
Chapter 9 – FOLDS, FAULTS & GEOLOGIC MAPS
Ductile Shear Zones!. ductile shear zone “zone”: area with higher strain than surrounding rock This is heterogeneous strain. “shear”: simple shear dominates.
Lineation. Lineation (Fig. 4.2, Passchier and Trouw, 1996) Any linear feature, –primary or secondary, that occurs –penetratively (at the outcrop and/or.
Lecture FIVE Metamorphic Textures
Chapter 10: Metamorphism: New Rocks from Old La Pietra by Michelangelo, carved from Carrera marble © 2012 John Wiley & Sons, Inc. All rights reserved.
Foliation and lineation Goal: To interpret some common types of foliation and lineation in deformed rocks.
Society of Earth Science Students A student-run club for all students interested in Earth Science, regardless of major. Activities: field trips, weekly.
Chapter 8 Metamorphism and Metamorphic Rocks. Metamorphism The transition of one rock into another by temperatures and/or pressures unlike those in which.
Shear zones and shear sense indicators Please read (D&R, pp )
What is it? What is it? (Quiz)
Metamorphic Rocks Change in mineralogy, texture or both of a pre-existing rock by application of heat and pressure Pre-existing rock can be either igneous,
Introduction to Folds (p ) 1)Nomenclature 2)Geometric analysis 3)More nomenclature 4)Fold mechanisms - flexural-slip folding - buckling - kink.
Dynamic Earth Class February 2005.
Structural Geology (Geol 305) Semester (071)
Announcements - Field trip in lab this week.
Structural Geology (Geol 305) Semester (071)
Metamorphic Rocks. Standards  Classify matter in a variety of ways  Describe the composition and structure of Earth’s materials, including: the major.
METAMORPHIC ROCKS. METAMORPHISM Alteration of any previously existing rocks by high pressures, high temperatures, and/or chemically active fluids.
CHAPTER 4 DEFORMATION AND STRAIN. Deformation describes the complete transformation from the initial to the final geometry (shape, position and orientation)
Metamorphic Rocks Foliations, and Lineations Topics Fabrics Foliation, cleavage, lineation –Cleavage and Folds –Geometry –Strain significance Origin.
Metamorphic Fabric Chapter 13A. Solid-state Crystal Growth Nucleation –Crystallization of new phases Crystal growth –Modification of existing grain boundaries.
Chapter 8: Metamorphism & Metamorphic Rocks
Determining strike and dip from geologic maps (revisited) 75 m.
Metamorphic Textures 2 - Regional T This part contains several color reproductions of Figures and Tables in your text. I will pass over them with a quick.
Metamorphic Rocks. What is a metamorphic rock? Rocks in which minerals, texture and/or structures have been changed by heat and/or pressure.
common to rocks affected by regional metamorphic compression typical of orogenic belts. characteristic of metamorphosed rocks in which minerals are aligned.
Lab 7 Metamorphic Rocks. Metamorphic rocks: –rocks changed by T, P, or action of watery hot fluids Protolith: –parent rock –can be ign, sed, mm.
Metamorphic Rocks. How do rocks change? Metamorphism causes changes in: Texture Mineralogy.
MECHANICS OF PLASTIC DEFORMATION > PLASTIC DEFORMATION IS BY FLOW; THE PROCESSES MAY BE: 1.INTERGRANULAR MOVEMENT A) DISPLACEMENT TAKES PLACE BETWEEN INDIVIDUAL.
Geology Rock Fabric. Objectives Attitudes of Fabric Attitudes of Fabric Cleavage Cleavage Lineations Lineations Foliations Foliations.
THE LANGUAGE OF THE EARTH – PART III
GLG310 Structural Geology. Announcements Reminder: Application exercise on Tuesday, Sept. 17 in class How do videos look and work? Homework questions?
Lecture 2: Deformation, reference frame,
Cleavage, foliation and lineation (Chapter 8 in Davis and Reynolds)
Today: Back to stress stress in the earth Strain Measuring Strain Strain Examples Today: Back to stress stress in the earth Strain Measuring Strain Strain.
Fold Folds form from curving, buckling, and bending of originally planar rock layers (e.g., beds, foliation) through ductile deformation Practically, folds.
Folds Field and Lab Measurements. Data Acquired for Folds Detailed structural analysis requires sampling of: – Bedding in sedimentary rock – Compositional.
Foliation.
Field work and Numerical modeling Summary Changcheng Sept.6,2008.
G EOL 2312 I GNEOUS AND M ETAMORPHIC P ETROLOGY Lecture 20 Introduction to Metamorphic Petrology March 23, 2009.
... the textural and mineralogical change rocks undergo when put under great heat and/or pressure. Metamorphism.
Room: 407 Tel: Patrice Rey.
GEOTECHNICS AND APPLIED GEOLOGY
METAMORPHISM: NEW ROCKS FROM OLD
STRUCTURE of METAMORPHIC ROCKS
Metamorphic Rocks Learning Goal: Understand how metamorphic rocks are formed and classified.
Metamorphic Rocks Metamorphic Rocks Definitions Definitions
METAMORPHIC ROCKS Rocks that form from other pre-existing rock (sedimentary, igneous, or metamorphic) that have been changed from high temperature and/or.
Metamorphic Rocks.
Metamorphic Rocks Chapter 7
Metamorphic Rocks Metamorphic Rocks Definitions Definitions
DEFINITION MECHANICAL PRINCIPLE: deals with the physical properties of rocks and the significance of these properties in rock deformation.
Origin of Cleavage and Schistosity
Metamorphic Rocks.
Deformed pebbles, Oolites and Mineral grains
Structural Geology Structural geology is the study of rocks deformed by stress and strain This involves trying to understand stress and strain forces to.
Metamorphic Rocks.
Lab 10: Strain Analysis.
Metamorphic Rocks & The Rock Cycle
Presentation transcript:

Announcements Draft #1 of fault paper due next Wed.! Late papers: lose 5% of grade per day.

Today: Cleavages and Passive Folding (Davis and Reynolds, pp )

Cleavage: closely spaced, aligned, planar surfaces; associated with folds- impart a splitting property to the rock- often cuts bedding

Cleavages: commonly parallel to axial planes of folds. They cut bedding! "Axial planar cleavage"

Cleavages: may fan slightly, but still close approximation for axial surface

Sometimes cleavages interact with fissility (tendency for rock to split along bedding plane) to form "pencil" structures

Cleavage can be very closely spaced- this is called a continuous cleavage (vs. a spaced cleavage)

Cleavage is an expression of variations in mineralogy and fabric (grain shape, size, and configuration)- these variations formed during deformation (secondary) "domainal" nature of cleavage

continuous cleavage under a microscope, showing domainal nature

Types of continuous cleavage: Purely based on grain size (which increases with higher T) (1) Slaty cleavage (fine-grained) (2) Phyllitic cleavage (med. grained- shiny) (3) Schistosity (coarse grained- can see micas)

Slaty cleavage

microfolds in mica layers "sheen" appearance phyllitic structure

Schistosity: coarser grained fabric

older layering can be folded + cut by younger cleavage to form Crenulation Cleavage

more... Crenulation Cleavage

Crenulation Cleavage at the microscopic scale

Strain Significance of Cleavage Relationship with folding: suggests cleavages form as a response to shortening and flattening Form perpendicular to  1 and S3 Confirmed in field and laboratory

How does cleavage form?? (1) Mechanical rotation of minerals (contributes a bit) (3) Pressure solution (dominant!!) 2) Directional Recrystallization (contributes a bit)

pressure solution "dimples" in conglomerate clasts

Formation of crenulation cleavage

stylolites- results of pressure solution in limestones

Passive Folds: wavelength shortened by pressure dissolution along cleavage planes

Passive Folds: generally similar folds- thickening in hinge zone. Intersection line between cleavage and bedding yields trend and plunge of hinge line!

Origin of Passive folds

TRANSPOSITION Lithologic layering is often mistaken for coherent bedding- it's not! It's layering due to major deformation cleavage/foliation is parallel to lithologic layering; lensoidal layers

How bedding gets transposed:

the beginning of limb destruction

destroy those limbs!

A lost limb due to transposition

transposition to the max!

Cleavage is a "flattening" fabric Pure shear (coaxial) vs. Simple shear (noncoaxial)? What about loss of volume?

What is it? What is the closely spaced fabric? Are these similar or parallel folds? Free folds, forced folds, or passive folds? What is direction of S1 (maximum stretch)? axial planar cleavage similar folds passive folds S1 is horizontal

Next Lecture: Foliations, lineations, and tectonites Please read (D&R, pp ; )

Important terminology/concepts cleavage axial planar cleavage continuous cleavage slaty cleavage phyllitic cleavage schistosity crenulation cleavage strain significance of cleavage pressure solution stylolites passive folds transposition flattening (pure shear) fabric volume loss (dilational strain)