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Flashcards in Economic Geology Deck (25):
1

What are Cu and Al used for?

wire, construction (aluminum)

2

What is Ge used for?

Semiconductors, transistors, and optics

3

Where does gold occur?

hydrothermal deposits, placers

4

Where are lead and magnesium found?

hydrothermal deposits

5

Where do most valuable metals occur?

most occur as atomic substitutions in more abundant rock-forming minerals

6

Where are most ore minerals found as?

Sulphides

7

ore minerals such as iron, tin, and tungsten occur as...

oxides

8

Define gangue

non-valuable minerals that metals occur in

9

Define hydrothermal mineral deposits?

minerals are concentrated by hot aqueous solutions flowing through fractures and pores in the substrate

10

Define magmatic mineral deposits

Formed by concentration of magmatic processes within a body of igneous

11

Define sedimentary mineral depostis

formed by precipitation from concetrated, modified sea water

12

How are placers formed?

Concentration by flowing surface water in streams
or along the shore

13

How residual minerals deposits are formed

Concentration by weathering processes

14

What three rules govern the formation of concentrated minerals

1. Source
rocks or magma
enriched in metals
that can be supplied
to the “
ore-forming”
system
2. Transport
melt or fluid
that can carry
metals from a
source to a site
of deposition
3. Trap
physical or
chemical process
that concentrates
the metals into
an ore deposit

15

Where are mineral deposits found?

Mineral deposits are found in a variety of plate
tectonic settings depending on where these
processes operate

16

Describe magmatic deposits from gravitational setting

heavy minerals that crystallize early, settle
and concentrate on the bottom of the magma
chamber

17

Some of the most important accumulations of
metals?

Associated with magma that forms igneous rocks

18

Describe magmatic deposits from immiscibility

• segregation of metal-rich (sulphide) liquid from the
crystallizing magma
• dense, metal-sulfide melt settles to the bottom of
the crystallizing magma chamber

19

Describe magmatic deposits in pegmatites

Made from melt remaining in last stages of crystalization of granitic magma which is rich in minerals. This liquid flows into cracks and creates large crystals

20

What are especially reactive carbonate-rich rocks which act as a chemical trap for metals

skarns

21

How are skarns made?

magma flows to marble like rocks, and the minerals are extracted out of the magma into the marble

22

Describe hydrothermal ore deposits

1. generated from hot water
2. originate from hot, metal-rich fluids
expelled from crystallizing intrusions
3. Fluids move along fractures, cool, and
precipitate the metallic ions to produce vein
deposits

23

Where are vein deposits concentrated?

areas of intense faulting

24

What are the two most common vein minerals?

quartz and calcite

25

Three places hydrothermal fluids come from?

Some originate when water dissolved in magma is
released as the magma crystallizes
• Some are formed from rainwater that circulates deep
in the crust, close to hot intrusions
• In the oceans, such as near midocean ridges, hot
seawater is circulated into the ocean crust