IGNEOUS PETROLOGY (MINERALOGY OF IGNEOUS ROCKS)

Question 1

Minerals which crystallize directly from magma?

Answer 1

Primary minerals

Question 2

Minerals which crytsalize in response to chemcal changes that affect an existing rock and sometimes act as replacement of primary minerals or infill of voids

Answer 2

Secondary Minerals

Question 3

These are mineral constiutents occuring in abundances of >5%

Answer 3

Major or Essential minerals

Question 4

less common minerals in concentrations of less than 5%?

Answer 4

Accessory minerals

Question 5

This is the proportion of mafic minerals in the total population of felsic and mafic minerals

Answer 5

Mafic index or color index (CI)

Question 6

<40%DCM

Answer 6

Felsic

Question 7

40-70%DCM

Answer 7

Intermediate

Question 8

70-90%DCM

Answer 8

Mafic

Question 9

> 90% dcM

Answer 9

Ultramafic

Question 10

<30

Answer 10

Leucocratic

Question 11

30-60

Answer 11

Mesocractic

Question 12

60-90

Answer 12

Melanocratic

Question 13

> 90

Answer 13

Hypermelanic

Question 14

IUGS 0-35% DCM

Answer 14

Leuco Cratic

Question 15

IUGS 35-65% DCM

Answer 15

Meso Cratic

Question 16

IUGS 65-100% DCM

Answer 16

Melano Cractic

Question 17

A direct type of Determination of rock composition by actual mineral id or Mineral Distribution

Answer 17

Modal composition or mode

Question 18

What types of ign rocks are suitable for modal composition?

Answer 18

Crystalline rocks

Question 19

Requires moving a thin section incrementally on a grid system such that at least 2000 mineral points are tabulated (300 for sandstone)

Answer 19

Point Counting Analysis

Question 20

An indirect scheme using data derived from chemical analysis of a rock sample
“Petrochemical Calculations”

Answer 20

Normatve Mineralogy

Question 21

This the first norm classification

Answer 21

CIPW (Cross, Iddings, Pearson, and Washington, 1902)

Question 22

What types of ign rocks are most suitable for normative classfiicaton?

Answer 22

Aphanitic and glassy

Question 23

a process that takes a rock bulk chemical composition and create a hypothetical set of minerals using that bulk chemical dataset

Answer 23

Norm

Question 24

what is the assupmtion in terms of Press and temp using normative classification?

Answer 24

(Surface Conditions)
Surficial temp,
low press and
anhydrous conditions

Question 25

what is the basis of acidity of rocks?

Answer 25

SiO2 content

Question 26

>45% SiO2

Answer 26

Ultrabasic

Question 27

45%-52% SiO2

Answer 27

Basic

Question 28

52-66% SiO2

Answer 28

Intermediate

Question 29

>66% SiO2

Answer 29

Felsic (Silicic)

Question 30

this implies that all avaialble cation oxides have been used to make normative minerals and additional SiO2 remains to generate normative qtz or free qtz

Answer 30

Silica Oversaturation

Question 31

rocks which contain normative fedlds and/or Opx (enstatite or hypersthene) minerals but lack either qtz or forsterite or feldspathoids

Answer 31

Silica Saturation

Question 32

This occurs when SiO2 is depleted before all oxides have been used to form normative minerals which normally are feldspathoids, forsterite

Answer 32

Silica undersaturation

Question 33

Rocks with unsually high Al2O3 content

Answer 33

Per Aluminous

Question 34

Rocks containing mafic minerals with ave aluminum cont

Answer 34

Met Aluminous

Question 35

Rocks containing mafic mienrals with low aluminum cont

Answer 35

Sub Aluminous

Question 36

Rocks contain normative or modal mineral with usually high K2O and/or Na2O

Answer 36

Per Alkaline