The Geology of Metallic Mineral Deposits (L20)

Question 1

what form was the metals first used by humans in?

Answer 1

pure elemental or native form

Question 2

what was smelting methods developed to do?

Answer 2

seperate metal from impure forms

Question 3

what are all metals united by having?

Answer 3

high electrical conductivity, lustre, and malleability, and the ability of their atoms to lose electrons to form positive ions

Question 4

what does the term “metal” generally refer to in our culture?

Answer 4

refers to “fusible metals” - metals of moderate hardness that can be fused with other metals to form alloys (metal mixtures)

Question 5

what are the 2 main categories we classify fusible metals in?

Answer 5

Precious metals and Base metals

Question 6

What are precious metals and why are they desireable?

Answer 6

metals of high intrinsic value (silver, gold, platinum)

desireable for the manufacture of electrical components due to their resistance to corrosion and oxidation

Question 7

what are base metals?

Answer 7

metals of low intrinsic value (iron, lead, copper, zinc, tin)

most base metals oxidize in air

Question 8

what was the term “base metals” derived from and what is it referred to now?

Answer 8

derived from the practice of alchemists to attempt to make gold from less valuable metals

the “base” part of the term now refers to base metals being common and inexpensive

Question 9

the metals that we think of as exceedingly common, are ____

Answer 9

actually scarce

Question 10

what is essential to the discovery of metal-rich deposits?

Answer 10

knowledge of the geological processes that lead to enrichment of metals, and of the geological environments in which the processes operate

Question 11

what is an important aspect in determining the feasibility of extracting any given metal?

Answer 11

cost of extraction

Question 12

a mineral body mined at a profit is called ___

Answer 12

an Ore

Question 13

What are some economic factors that qualify a mineral body to be called an Ore?

Answer 13

the concentration of the metals of interest and the size of it
the cost associated with mining and transportation
market value of the metal

Question 14

some metals, such as iron and chromium can be concentrated by _____

Answer 14

gravitational setting

Question 15

what is an example of gravitational setting?

Answer 15

heavy oxide minerals are formed during the earliest stages of cool and sink to the bottom of the magma champer

the rest of the minerals fill the remaining spaces, and the least dense minerals can actually float to the top of the magma chamber

Question 16

What is immiscibility?

Answer 16

an “unmixing” or seperation of metal-rich liquid from silicate-rich liquid

Question 17

how does immiscibility work?

Answer 17

as the molten material rise to the surface, metal-rich liquid seperate from the silicate liquid by settling to the bottom while the silicate material floats to the top

Question 18

what is one of the best-known and most important ore deposits? How is it created?

Answer 18

ore deposits formed from hydrothermal (hot-water) solutions

these solutions may be left over fluids of cooled magma, or generated by the warming of groundwater or seawater that seep into rock below the surface by heat

Question 19

what is a critical factor in the ability of hot water to dissolve metals?

Answer 19

its “saltiness”

Question 20

higher the water temp, _____?

Answer 20

greater the amount of material the water can dissolve and hold in solution

Question 21

what can be generated from the pressure from the intrusion of an igneous body?

Answer 21

it can generate lots of microscopic cracks into which residual fluid from the intrusion can penetrate and cool

these dissemenated ore deposits low in grade but mined at a profit

Question 22

how are mineral-filled veins created?

Answer 22

fluids super-concentrated in metals penetrate larger fractures

Question 23

what is another word for Vein Deposits?

Answer 23

Lode Deposits - comes from “Mother Lode”

Question 24

what can be found in these mineral-filled veins?

Answer 24

native gold and silver can be found in the spaces between quartz crystals within these veins

Question 25

how are the gold-bearing quartz veins made of?

Answer 25

made of minerals that percipated in large cracks in the rock when it was still deep undergound

Question 26

why is gold found in close association with quartz?

Answer 26

quartz crystallizes at low temps. the fluids containing dissolved gold are left over after the main rock-forming minerals have crystalized into plutonic igneous rocks

Question 27

what is Pegmatite?

Answer 27

rock type associated with late crystalization that crystalizes from water-rich residual magma that tends to occur on the borders of large intrusions and can also be injected into smaller scale fractures

Question 28

how are the huge crystals found in pegmatites?

Answer 28

the huge crystals are due to the very fluid-rich nature of the magma

b/c ions are able to move around easily and react with each other, crystals grow to huge sizes