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Ore deposits > Lec 8 - Orthomagmatic deposits > Flashcards

Lec 8 - Orthomagmatic deposits Flashcards

1
Q

Deposits that ofrmfrom coolinga fn crystallization of magma

A

Magmatic deposit

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2
Q

Characteristics of magmatic deposits

A
  1. Occurs near the magma or intrusives
  2. Simple mineralogy and products yield are not numerous
  3. May occur as strata-like segregationss, as dissemination and as vein-like injection
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3
Q

True or False: magmatix textures are mostly the same with parent igneous rock

A

Trueness

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4
Q

The gradationbetween magmatic segregation and hydrothermal activity is manifested by _____________

A

Wall-rock alteration effect

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5
Q
  • Igneous rocks defined by mineralogical composition consisting of more than 50% carbonate
  • associated with continental rift-related settings
  • occurs as small plugs, dikes, sills, veins
A

Carbonatites

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6
Q

Metal concentration in magma

A

Low degrees of partial melting

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7
Q

Most recent carbonatites are found in the _____________

A

East African Rift

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8
Q

Separation of crystallizing minerals based on gravitative differentiation

A

Magmatic segregation

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9
Q

Formed by accumulation of crystals either by floating or settling

A

Cumulate rocks

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10
Q

Titanium deposits

A

Anorthosite

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11
Q

__________ is a lithophile element compatible in both spinel and clinopyroxene relative to ultramafic and mafic melts

A

Chromite

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12
Q

Proterozoic anorthosite massifs: more shallowly derived by partial melting or contaminated by lower continental crust meterials

A

Ilmenite-rich andesine-typr

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13
Q

Proterozoic anorthosite massifs: differentiates of an anorthosite-gabbro magma

A

Magnetite-ilmenite-rich labradorite-type

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14
Q
  • Chromite is hosted in ultramafic layered intrusions composed of cumulus crystals
  • consists of thin but laterally continuous layers of chromite
A

Stratiform Chromite Deposit

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15
Q
  • Pipe-like to pod-like masses of chromite in dunite-harzburgite sequences
  • related to ophiolites
  • a.k.a. Orogenic-type chromite or alpine-type chromite
A

Podiform chromite

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16
Q

When liquids do not mix

A

Liquid immiscibility

17
Q

3 kind of liquid immiscibility

A
  • silicate-carbonate
  • silicate-oxide
  • silicate-sulfide
18
Q

Massive Ni-Cu broadly oayered from mafic to less mafic going upwards

A

Host intrusions

19
Q

Sudbury Igneous Complex

A

Ni-Cu magmatic deposit

20
Q

Bvshveld Complex

A

Stratiform Chromite Deposit

21
Q

A high MgO volcanic flow

A

Komatiite

22
Q

A texture produced by intergrowth and interpenetration of long, skeletal quench crystals of olivine and pyroxene

A

Spinifex

23
Q

Repititious oscillation from rock type upward within tye complex. Presumably the repititions represent periodic depletions of critical cations in magma chamber

A

Rhythmic layering

24
Q

Systematic variation in certain elements within a complex. Indicates differentiation from a single parent magma, as periodic reinjections of new magma would not allow cryptic layering

A

Cryptic Layering

25
Q

Removal and segregation of mineral precipitates from a melt

A

Crystal fractionation

26
Q

Formed from the last crystallizing magma enriched in vapor and water pressure

  • 250-750 degrees celcius
  • associated with plutonic or regional metamorphism
A

Pegmatites

27
Q

Formed from one period crystallization: after injection of hydrous siliceous late-stage melt

A

Zone or Heterogenous Pegmatite

28
Q

Peralkaline igenous complex

A

Pegmatites

29
Q
  • Alkaline, volatile-rich potassic, low density ultrabasic magmas
  • formed as small degree partial melts of carbonate-bearing and hydrous mantle peridotite
  • occurs as diatremes
A

Kimberlites

30
Q

As hot kimberlite magmas >900 C is heated near-surface ground waters, water flashes to steam and results in explosive activity

A

Diatreme formation

31
Q

Forms in a thick, old, relatively cool “keel” of archean crust

A

Diamonds

32
Q

1 carat is equal to?

A

200 mg or 0.2 g

33
Q

Diamonds do not originate in the kimberlite/lamproite, they only provide the transport

A

Remeber

34
Q

2 TYPE OF DIAMONDS

A
  • P-type derived from peridotite

* E-type derived from eclogite

35
Q

Significant diamondiferous kimberlites occur only in ancient shield regions, including archean cratons and paleoproterozoic mobile belts that border archean cratons, and were themselve underformed since the end of paleoproterozoic era

A

Clifford’s rule

36
Q

Types of Kimberlites

A
  • Group 1 - recognized world wide, forsterite in serpentinite-carbonate matrix
  • Group 2- S. Africa, phlogopite in olvine-mica ground mass
  • Lamproite - australia and India, Ti-phlogopite, Ti-K richterite, olivine, diopside, sanidine

Ore deposits (8 decks)

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