Earth resources main geology

Question 1

What are the four types of hydrothermal or deposit

Answer 1

Porphyry deposits, VMS ( Volcanic hosted massive sulphide deposits. Epithermal deposits, Geothermal sites and hot springs.

Question 2

Explain porphyry deposits

Answer 2

Hydrothermal systems associated with magma chambers often form porphyry copper deposits.
These are large, low grade ore bodies. Contain gold and Molybdenum.
Copper commonly found as copper sulphites that precipitate from cooling hydrothermal fluids.

Question 3

Explain VMS deposits

Answer 3

Usually occur at mid ocean ridges, or other volcanic environments.
Created deposits the are rich in metals like zinc, coper and led, often accompanied by precious metals like gold and silver.
The deposits form when mineral rich fluids react with sea water.

Question 4

Explain Epithermal deposits

Answer 4

Form at shallower depths and are associated with high temperature hydrothermal systems.
Rich in gold, silver, and copper and are often found I geological regions.

Question 5

Explain geothermal systems and hot springs.

Answer 5

In geothermal fields, hot water or steam is extracted from underground reservoirs to generate energy.The mineral deposited in these systems can form silica sinters or travertine deposits at the surface.

Question 6

What are silica sinters

Answer 6

Silica sinters also known as silica deposits are are chemical precipitates primarily composed of amorphous silica, that from as hot, mineral rich fluids cool and deposit their dissolved silica content.

Question 7

What are travertine deposits

Answer 7

travertine is a a type of sedimentary rock that forms from the precipitation of calcium carbonate in geothermal or cave environments, often associated with hot springs, limestone caves and tufa formations.

Question 8

What is goldschmidts classification

Answer 8

Is a geochemical classification of the elements that group them into four categories based on their preferred host phase.

Question 9

Lithophile

Answer 9

Elements that are attracted to rock. These elements are concentrated in the silicate protein of the earth, such as crust and mantle.

Question 10

Siderophile

Answer 10

Elements that are attracted to the iron metal. These elements partition into the FE rich metal of planetary cores.

Question 11

Chalcophile

Answer 11

These are elements that are attracted to sulphur or said to be chalcogen loving.

Question 12

Atmophile

Answer 12

Elements that are attached to the atmosphere. Are either gases or form volatile hydrides.

Question 13

Explain layered Mafic intrusions

Answer 13

Layers mafic intrusions are large, often tabular bodies of mafic igneous rock (rich in magnesium and iron).
They exhibit distinct layers or stratification.
associated with magmatic differentiation processes.
Are also important on an economical perspective as they often contain important mineral deposits such as PGE (Platinum group elements), and nickel copper sulphides.

Question 14

What are Komatiites

Answer 14

Komatiites are a type of ultramafic igneous rock that are rich in magnesium and iron, with very low silica content.
High temperature of forming and unique mineralogy.
High olivine and pyroxene content.

Question 15

What are the different PGMs

Answer 15

Platinum (Pt)
Palladium (Pd)
Ruthenium (Ru)
Rhodium (Rh)
Iridium (Ir)
Osmium (Os)

Question 16

Where are PGMs typically found

Answer 16

They are typically found In mafic and ultramafic igneous rocks, where they are associated with other minerals such as chromite and Nickel.
Can be based off of their mineralogical and chemical properties.

Question 17

What is chromite and sulphide

Answer 17

Chromite, is an iron-chromium oxide mineral that is the primary ore of chromium a, critical mineral used in the production of stainless steel, alloys and in various industrial applications.
Sulphides are another major group of metals commonly found in mafic and ultramafic intrusions. These mineral often crystallise in cumulative layers.

Question 18

Why do some minerals form in cumulative layer and others don’t.

Answer 18

Some key factors that influence layered accumulation of minerals includes
Crystallisation order and Bowens reaction series, density differences (gravitational settling), magmatic differentiation and fractional crystallisation, viscosity of the magma, magma stratification and cooling rate, and magma composition.

Other minerals do not form as minerals with similar densities to the surrounding melt do not settle out to form distinct layers.
Minerals that crystallise later in the cooling process like felspar and quartz do not form layers because they are typically the last to crystallise and remain suspended in the remaining magma.
Minerals that are soluble in the magma of form solid solutions with the met tend to crystallise more uniformly throughout the rock, such as alkali feldspar or muscovite.

In summary
Minerals that form accumulative layers (such as chromite, olivine, pyroxene, sulfides) are typically early-crystallizing, dense, and less soluble in the remaining melt. They tend to settle under gravity as the magma cools and crystallizes, forming layered deposits in the lower portions of a magma chamber.

Minerals that do not form accumulative layers (like feldspar, quartz) tend to crystallize later, are less dense, and crystallize more uniformly throughout the magma without forming distinct layers.

Question 19

Bowens reaction series

Answer 19

Describes the sequence in which minerals crystallise from cooing magma.
Split into two main branches, one being the Discontinuous series and the other being the continues series.

The discontinuous series refers to the minerals that crystallise at distinct temperatures, and as one minerals forms it reacts with the surrounding melt to produce a different mineral. These minerals form in a specific order based on temperature and mineral composition.

The continuous series include minerals that gradually evolve. Describes the crystallisation of feldspars and the gradual changes in their chemical composition as the temperature decreases. Th primary change here is the substitution of Calcium with Sodium in the Feldspar crystals.

The final stage of it is low temperature minerals.
At even lower temperatures, typically below 700 degrees, minerals like quartz and potassium feldspar, (orthoclase) begin to crystallise. Quartz crystallises at the lowest temperature, (600 - 800 degrees celsius) as the magma becomes silica rich and relatively depleted in minerals like iron magnesium and calcium.
Pottasium feldspar crystallises after quartz at temperatures around, 650 to 750. It typically contains potassium along with aluminium and silica.
At even lower temperatures, 500 - 700 degrees. Muscovite a type of mica, can form in some magmas, particularly in those rich in aluminium and potassium.

Question 20

Sate the discontinuous series minerals in order of first mineral to crystallise to the last.

Answer 20

Olivine
pyroxene
Amphibole
Biotite

Question 21

What is gravitational settling

Answer 21

Gravitational settling in geology refers to the process by which minerals or crystals that form from cooling magma sink to the bottom of a body of liquid due to their higher density compared to the surrounding material. This process plays an important role in the formation of a variety of igneous and sedimentary rocks, particularly in the formation of layering systems.

Question 22

Explain magmatic differentiation and fractional crystallisation

Answer 22

Magmatic differentiation is a geological process that occurs when a single body of magma evolves into chemically distinct types of rocks through the selective crystallisation and movement.

Types of magma differentiation

Primary Differentiation (from a single magma). This occurs when a single body of magma undergoes fractional crystallisation and crystal settling

Question 23

What is an I type granite

Answer 23

A mantle dominated system, created through the factional crystallisation of basaltic melt.

Question 24

What is an S type granite

Answer 24

A crust dominated system, with partial melting of crustal rocks.