IGNEOUS PETROLOGY (INTRUSIVES)

Question 1

Plutons oriented parallel to the pre-exitsing layering (or if no visible layering to the earth’s surface) are said to be

Answer 1

Concordant

Question 2

Plutons that cuts across the country rocks or if it is inclined at an angle to the surface of the Earth

Answer 2

Discordant

Question 3

Stocks are plutons with surface exposure of

Answer 3

less than 100 sq.km

Question 4

Batholiths are irregularly shaped plutons with surface exposure of

Answer 4

more than 100 sq. km

Question 5

will the total size of the pluton matter?

Answer 5

No, only the exposed parts

Question 6

Divergent margin and hotpot Batholits and Stocks are composed of

Answer 6

Gabbroic

Question 7

Convergent Margin batholits are generally

Answer 7

Intermediate to silicic
Diorite
Granodiorite
Qtx Diorite
or Granite

Question 8

A batholith pattern with alternating mafic and felsic mineral layers which may involve multiple dike like intrusion and/or fractionation

Answer 8

Pinstripe Pattern

Question 9

A tabular concordant pluton that parallels the country rocks and have a mutually perpendicular long and hort dimension caused by injection of magma along a plane of weakness parallel to the layering in thre country rocks

Answer 9

Sill

Question 10

A blister like (Pimple like) concordant plutin with a flat floor and domed roof which is foemed due to intrusion of additional magma creating a convex roof structure

Answer 10

Laccolith

Question 11

Dishshaped or funnel shaped concodrant plutons resembleing a chamnagle class whih can develop either due to meteorite impact, Normal Faulting and crustal melting assodicated with rifting or sill like structures which received upwelling of magma from a conical feeder tube

Answer 11

Loppolith

Question 12

Famous Loppolith formation

Answer 12

Sudbury, Canada
Skaergaard, Greenland
Bushveld, South Africa
Koillismaa, Finlands
Muskox, Canada

Question 13

Forms as hot fluids flow though fractures then cool and crystallize which may be concordant or discordant to the surrounding country rock

Answer 13

Veins

Question 14

Great abundance of veins

Answer 14

Vein Swarms

Question 15

Veins that are perpendicular

Answer 15

Orthogonal

Question 16

Veins that are parallel

Answer 16

En Echelon

Question 17

Veins that are S shaped and parallel

Answer 17

Sigmoidal

Question 18

Cylindrical plutonic bodies exposed at the surface by subsequent erosion which represent ancient conduit pipes which funneled magma upward to a volcano that has long since been removed by erosion

Answer 18

Necks

Question 19

Carrot shaped cylindrical pipes that can extend to depths of 200km and develop via EXPLOSIVE INTRUSIONS that origniate deep within the mantle

Answer 19

Diatreme

Question 20

Why are these carrot shaped cylindrical pipes intrude explosively?

Answer 20

Because of High Volatile Content

Question 21

What type of volcanoes may form on top of diatremes?

Answer 21

Tuff Cones

Question 22

Intrusions that cross-cut country rock layers and are typically more resistant to weathering and eorion than surroounding country rock and exposed commonly from topographically elevated ridges

Answer 22

Dikes

Question 23

Where is the Great Dike situated?

Answer 23

Zimbabwe and Southe Africa

Question 24

What deposits are found in the great dike

Answer 24

PGE and Chromites

Question 25

Consists of multiple dikes that can occur either parallel, sub-parallel, radiating, concentric or random

Answer 25

Dike Swarms

Question 26

forme when vertical forces related to rising magma produce fracture that radiate outward from the central vent and is injected with magma

Answer 26

Radial dikes

Question 27

Formed when a cocentric fractures are nearly vertical and circular in Map View and is intruded by the magma

Answer 27

Ring Dikes

Question 28

Dike tha form when a a converging circular fracture is injected by Magma

Answer 28

Cone Sheet Dikes

Question 29

Consists of parallel, offset dikes that form in response to shear

Answer 29

En Enchelon Dikes

Question 30

Form perpendicular extension and are common in rift environment

Answer 30

Parallel Dikes

Question 31

Steeply inclined dikes composed of grabbro, diabase and basalt that forms a certain layer of the ocean floo and form by the cooling and contraction of magma as it is repeteadly injected into the extensional fractures in oceanic rift valleys. Repeated injections is the one responsible for the formation of parallel dikes

Answer 31

Sheeted Dikes

Question 32

what layer of the ophiolite sequence corresponds to such dikes?

Answer 32

2B (2A-Pillow Basalt and overly plutonic gabbroic rocks)

Question 33

Cylindrical plutonic bodies due to highly viscous magma no erosion

Answer 33

Bysmalith

Question 34

When magma occupies spaces along folded crests and troughs of a thick sed sequence

Answer 34

Phacolith