EES UNIT 3

metamorphism

• when a rock’s minerals and textures change

• due to prolonged temperatures and pressure

load pressure

• uniform pressure which acts equally in all directions

directed pressure

• when pressure is applied in a particular direction

contact metamorphism

• when a rock is subjected to high temperature

• occurs in upper levels of the earth’s crust

aureole

• a zone of metamorphism surrounding an igneous intrusion

• typically characterized by changes in mineralogy and texture

regional metamorphism

• metamorphism that occurs over large distances

• typically associated with tectonic forces

dynamic metamorphism

• metamorphism that occurs due to intense pressure and deformation

• caused by tectonic activity, usually in fault zones

metamorphic grade

• the intensity of metamorphic conditions affecting a rock

protolith

• the parent rock from which a metamorphic rock forms

prograde

• the process of increasing metamorphic grade due to rising temperature and pressure

retrograde

• the process of decreasing metamorphic grade due to lowering temperature and pressure

foliation

• alignment of mineral grains along parallel planes

• due to directional pressure

slaty cleavage

• in low grade

• sheet silicate minerals (mica and chlorite) recrystallise in a preferred orientation

• found in fine-grained rocks

schistosity

• in intermediate grade

• found in medium to coarse grained

• visible layering, often including biotite and mica

gnessic texture

• high grade

• coarse grained

• distinct banding of light and dark minerals

dehydration

• when a rock is heated, water is expelled to recrystallise

• occurs in minerals formed at low temps (which contain more water)

decarbonation

• when carbon dioxide is expelled

• occurs in minerals formed at high temps

metasomatism

• process of chemical alteration of a rock by hot fluids

• results in changes to its mineral composition and often involving the addition or removal of elements

recrystallisation

• where minerals in a rock change in size and shape

• without changing their chemical composition

• often due to heat and pressure

realignment

• process where mineral grains in a rock are reoriented due to stress and pressure

• often results in foliation or banding of the rock

acronym for index minerals

• Silly Kangaroos Stalk Grass Before Christmas

• this is high to low grade

index minerals (from high to low grade)

• sillimanite

• kyanite

• staurolite

• garnet

• biotite

• chlorite

syncline

where sediments dip towards each other

anticline

when sediments dip away from each other

dykes

• vertical intrusions of magma which has been cooled down

extrusive igneous rocks on a cross section

• sit on top of the other rocks

• but do not extend below the surface significantly

intrusive igneous rocks

• extend to a significant depth below the surface

unconformity

• represent a break in deposition of sediments over time

angular unconformity

• when an unconformity has early beds folded

• over time, the tilted beds are covered up by horizontal layers

nonconformity

• where sedimentary layers overlie older igneous rocks

slate

• low grade

• very fine grained

• slaty cleavage

• dark grey rock

• dull lustre

• protolith: shale

• associated minerals: chlorite, muscovite

phyllite

• low-medium grade (between slate and schist)

• fine grained (larger than slate)

• parallel platy texture

• protolith: shale/mudstone

• associated minerals: chlorite, muscovite

schist

• intermediate grade

• medium-coarse grained

• schistosity

• visible grains of mica

• shiny lustre

• protolith: shale

• associated minerals: biotite, feldspar, silimanite

gneiss

• high grade

• coarse grained

• mineral banding of alternating layers of light and dark minerals

• associated minerals: garnet, staurolite, kyanite, silimanite

amphibolite

• intermediate grade

• medium-coarse grained

• protolith: basalt/gabbro

• composed of dark rock (hornblende)

• not foliated

quartzite

• intermediate-high grade

• protolith: sandstone

• sugary granular texture

• not foliated

marble

• low-intermediate grade

• associated mineral: calcite

• calcite crystals recrystallise

• protolith: limestone

ecosystem

a community of living organisms interacting with their environment, providing essential services

renewable resource

• a natural resource that replenishes at a rate faster or equal to the rate of its consumption

• is considered sustainable

main categories of renewable resources

• managed resources

• ecosystem services

• renewable energy resources

managed resource

• a resource which is actively overseen and protected to ensure sustainable use

• it is harvested at a rate which enables them to renew

ecosystem service

• renewable processes that play a vital role in human survival and quality of life

• consist of supporting, provisioning, and regulating

geothermal energy

• thermal energy generated and stored within the earth

• partly derived from the ongoing decay of radioactive isotopes

how is GE harnessed from direct use systems?

• utilise heat from sources, like geothermal reservoirs or hot springs

• which provides heating directly

how is GE harnessed from EGS’s?

• cold water is pumped down into an injection of hot dry rock

• water travels through fractures in the rock, captures heat along the way

• this is then converted to electricity via a steam turbine or power plant

factors when evaluating a location for GE

• proximity to cities

• availability of land

• legal permissions

• permeability of high heat source rock

• availability of water

supporting service

• the foundational natural processes and structures that allow all other ecosystem benefits to exist

examples of supporting services

• nutrient cycling

• soil formation

• cycling of gases

provisioning services

• the tangible, material goods that are obtained from nature

examples of provisioning services

• timber

• water

• food

• fuel

regulating service

• is the benefits provided through the moderation and stability of the environment

• acts as the earth’s life-support system by managing nature

• operates on a local and global scale

examples of regulating services

• carbon storage

• flood regulation

• water purification

• climate regulation

• disease regulation

non renewable resource

• a natural resource which cannot be replenished at a pace to keep up its consumption

• exists in finite amounts

ore mineral

• a mineral from which metals/compounds can be extracted

gangue mineral

• a mineral of little to no worth

• is removed when extracting a desired mineral

why might a mineral be considered gangue initially?

• it may become useful later on in time due finding new applications for the mineral's properties

• it may not appear to have a valuable mineral

ore body

• sum of ore minerals

• gangue minerals

• surrounding material which requires extraction of desired metal

ore grade

• measurement of concentration of metal in an ore

deposit

• a known quantity of ore minerals

resource

• a deposit that can be economically mined

magmatic ore

• ore deposits formed from the crystallization of magma

vms deposits

• formed from hot, saline, metal rich fluids exhaled from sea-floor vents

• major sources of zinc, copper, lead

intrusive ore deposits

• formed from the cooling and solidification of magma within the earth

magmatic differentiation

• The process by which different minerals crystallize from cooling magma at different temperatures

• results in various rock types and compositions

magmatic segregation during differentiation

• The process in which minerals separate from magma due to differences in density, size, or solubility during cooling.

• leads to the formation of concentrated ore deposits

gravitational settling (chromite)

• where denser, early formed minerals settle out of molten rock as it cools and solidifies under the influence of gravity

• these sink to the base and form a cumulate layer

volatile transport (pegmatite)

• as magma crystallises, lower solubility minerals crystallise

• magma becomes felsic and is water rich

• water is highly mobile and has dissolved ions

• thus can enter fractures to form pegmatite dykes

immiscible separation

• when magma can physically separate into silicate and sulfur rich

• sulfur rich is heavier and sinks to base

hydrothermal alteration

• when hydrothermal fluids circulate through rocks and react

• this changes mineralogy of the rock

• forms an alteration halo

placer deposits

• concentrations of valuable minerals formed by the gravitational settling of materials in water

how is a mineral in a placer deposit concentrated?

• resistant to weathering/erosion

• relatively high specific gravity

regional metamorphism and metamorphic ores

• metamorphism can form economic concentrations

• this enlarges the grain size of the ore minerals

• generates hydrothermal fluids which can collect and transport economic minerals

how are fossil fuels formed

• plant/animal remains combined with a large supply of organic matter to accumulate

• anaerobic environment (oxygen poor) so that decomposition occurs slowly

coalification

• process by which plant material transforms into coal over millions of years

how is coal formed

• forms from buried tissues of plants like trees

• form largely in swampy environments

• mud prevents air to interact → anaerobic environment

• plant material accumulates and compressed → peat

• peat is buried deeper due to mass

• increased temperature and pressure reduce moisture

• increases carbon content

list all coal types

• peat (most impure)

• lignite

• sub-bituminous

• bituminous

• anthracite (very pure)

how is coal quality determined

• moisture (lower the better)

• ash content (lower the better)

• volatiles (lower the better)

• amount of carbon (higher the better)

how was oil and natural gas formed

• oceans consisted of plankton

• plankton and organic material accumulated on the ocean floor

• these formed muds

• progressive burial led to increased temp and pressure, converting matter into kerogen

• further temp increase causes kerogen to release droplets of liquid hydrocarbon

outline the prior steps required when mining for a resource

• decide what deposit is being explored

• decide the location and research the area

• assess environmental impacts

• application for a license

remote sensing

• the acquisition of information about an area from a distance

• typically uses satellite or aerial imagery to gather data without physical contact

satellite imagery

• used in remote sensing to capture detailed images

• is used commonly due to its low cost

electromagnetic induction

• measures the electroconductivity of a subsurface

• highly conductive minerals will show a higher response to electromagnetic fields

• used for nickel, copper, oil exploration

gravity surveys

• used to measure variations in the Earth's gravitational field.

• helpful in identifying subsurface structures and mineral deposits

• used in geological mapping and iron/gold exploration

magnetic surveys

• utilize magnetic field measurements to detect subsurface anomalies

• contrast magnetic susceptibilities of the mineral against the earth’s magnetic field

• used for geological mapping

radiometric surveys

• detects natural gamma radiation from earths elements

• used for geological mapping

stream sampling

• involves collecting samples from natural water bodies to assess mineral content and contamination

• samples are analysed for trace amounts of ore minerals

rock chip sampling

• involves small rock fragments, across a grid like pattern of the area

• used to map the subsurface zones of mineralisation

soil sampling

• analyzing soil from specific depths to detect trace elements and ore-body mineralization beneath the surface

• sample is sent to a lab for chemical analysis

reverse circulation

• uses high-pressure air to bring rock cuttings to the surface

• is faster than diamond drilling and is cheap

diamond drilling

• uses a diamond-encrusted bit to extract cores from the ground

• is the common method

• is quite slow

why are both geophyiscal and geochemical techniques used?

• geophysical provides a large scale information

• geochemical provides finer information which is relevant to discovery

• geochemical also assesses the grade and distribution of mineral

• economic potential also cannot be established without grade

open cut mining

• used when the deposit lies closely to the surface

• dug downwards in successive intervals

• minerals typically extracted are iron, coal, gold, copper

underground mining

• used when the ore is situated deep

• cost of removing overburden to expose ore > potential of ore

environmental impact assessment

• an assessment of the possible impacts that a proposed project may have on the environment

why are cultural heritage assessments important?

• they identify and evaluate the potential effects of a project on historically or culturally significant sites

• ensuring its preservation while aligning with ethical and legal standards

environmental impacts of mining

• acid mine drainage

• tailings dam risks

• pollution

how is acid mine drainage treated?

• covered with clay

• followed by neutralisation, through limestone

eutrophication

• is the process of nutrient enrichment in water bodies

• leading to excessive growth of algae

• deterioration of water quality.

how does eutrophication work?

• excess nutrients (nitrogen and phosphorus) are added

• causes algae blooms

• eventually algae dies and produces organic matter which sinks to bottom

• decomposition happens and O2 levels are depleted

• depletion of oxygen results in the death of species

impacts of eutrophication

• loss of biodiversity

• toxic algal blooms

• disruption of aquatic ecosystems

• poor water quality