MINERAL DEPOSITS FINALS REVIEWER

Weathering

is a process of physical disintegration of rocks at the surface of the Earth and chemical changes of their minerals.

-Mechanical/Physical weathering

-Chemical weathering

-Organic/Biological Weathering

Weathering processes can be divided into:

Physical and Chemical

______ and ____weathering can be driven by inorganic or biochemical reactions

Placer Deposit

Form by weathering and decomposition of rocks which contain a mineral of economic interest.

Bauxite

is formed by the thorough weathering of many different rocks. Clay minerals commonly represent intermediate stages

Nickel Laterite

deposits derived from the weathering of underlying ultramafic rocks found along the ophiolite belts of the country form the bulk of nickel deposits.

Supergene Enrichment

_____ where leaching of materials occurs and precipitation at depth produces higher concentrations. An existing mineral deposit can be turned into a more highly concentrated mineral deposit by weathering in a process

EVAPORITES

•Mineral deposits resulting from the concentration and crystallization by evaporation from aqueous solutions 

•Can be considered as sedimentary rock formed by chemical sediments

•Can be found in both marine and non-marine environments

Deposition of minerals by evaporation depends on supersaturation, which in turn depends upon other factors, chief of which are:

a)    temperature

b)   pressure

c)    depositional environment, and

d)   seasonal & climatic changes

e)   Solubility contents

BURIED DEPOSITS

▪Evaporite deposits that formed during various warming Seasonal and climatic change periods of geologic times.

Messinian Salinity Crisis

▪The most significant known evaporite depositions happened during the _____ in the basin of the Mediterranean

BRINE DEPOSITS

▪Evaporite deposits that formed from evaporation:

Ocean water

the prime source of minerals formed by evaporation)

Hypersaline

solutions derived from normal sea water by evaporation are said to be

Glaciers

_____ are powerful enough to carry tiny and huge rock debris, and when they drop it, the ice drops it indiscriminantly

TILL

Thus, material deposited by ice is unsorted or mixed in size. This non-sorted material is called ___

retreat

refers to the front or outer edge of the ice,

MELTWATER

Water running off of the ice is

BEACH PLACER

Result of the action of shore currents and waves which tend to sort and distribute the materials broken down from the sea cliffs or washed into the sea by streams.

BAJADA PLACER

A name applied to a certain peculiar type of ‘desert’ or ‘dry’ placer. Similar to alluvial placer except as it is conditioned by the climate and topography of the arid region in which the placer occurs.

AEOLIAN

Local concentrations caused by the removal of lighter materials by the wind, which blows the lighter rock particles or sand away from a body of low-value material, leaving behind surface veneer containing heavy minerals

PALEO-PLACER

ancient placers which have subsequently been buried and metamorphosed into a solid rock.

GLACIAL PLACERS

Since it is the habit of a glacier to scrape off loose debris and soil but not to sort it at all, ice is wholly ineffective as agency of concentration for metals. Gold derived from the outcrops of small veins is thus mixed with large masses of barren earth

ELUVIAL OR RESIDUAL PLACER

Derived by in situ weathering or weathering plus gravitational movement or accumulation.

They are found in the form of irregular sheets of surface detritus and soil mantling a hillside below a vein or other source of valuable mineral.

ALLUVIAL PLACER

One of the most common types of placer deposits

Placers consist of sands and gravels sorted by the action of running water.

If they have undergone two or more periods of erosion, and have been resorted, the result will in all probability be  a comparatively high degree of concentration of the heavier mineral grains.

PLACER DEPOSIT

Accumulations of valuable minerals concentrated in overburden, in stream sediments or in beach materials by natural processes.Concentration of heavy minerals by streams, waves - Gold, tin, garnet, ilmenite

DIAGENESIS

“All changes to sediment/sedimentary rocks from the time of deposition to the onset of metamorphism ”

MVT Pb-Zn

are a varied family of epigenetic ore deposits that form predominantly in dolostone and in which lead and zinc are the major commodities. Most are found in rocks of Cambrian and Ordovician, Devonian and Carboniferous, and Triassic ages.

SEDIMENTARY EXHALTIVES (SEDEX)
DEPOSITS

deposits are stratiform, massive sulphide lenses formed in local basins on the seafloor. This is usually as a result of hydrothermal activity in areas of continental rifting.

Stratiform

Concordant with bedding; usually in sheets but may be ribbon-like

BOG IRON DEPOSITS

typically small and thin, and comprise concentrations of goethite and limonite (Fe–oxyhydroxides) associated with organic-rich shale

IRONSTONE DEPOSITS

form in shallow marine and deltaic environments and typically consist of goethite and hematite that has been rolled into oolites or pellets, suggesting the action of mechanical abrasion

BANDED IRON FORMATION (BIF)

•Represent the most important global source of iron ore and far outweigh the ironstone and bog iron ores in terms of reserves and total production

•Thinly bedded or laminated chemical sediments containing 15% or more Fe (typically 25 – 35%) of sedimentary origin, commonly but not necessarily containing layers of chert.

ALGOMA TYPE

▪consist mainly of oxide(magnetite and hematite content) and carbonate lithofacies that contain 20 to 40 % Fe as alternating layers and beds of micro- to macro-banded chert or quartz, magnetite, hematite, pyrite, pyrrhotite, iron carbonates, iron silicates and manganese oxide and carbonate minerals

LAKE SUPERIOR

▪Thinly banded; oxide, carbonate and silicate facies

▪located on stable continental platforms and were mainly deposited in Paleoproterozoic times and formed on continental-margins, without direct relationships with volcanic rocks

RAPITAN

▪represent a rather unusual occurrence of iron ores associated with glaciogenic sediments formed during the major Neoproterozoic ice ages

MANGANESE
DEPOSITS

considered to have formed as a result of submarine volcanism form in shallow, near-shore environments and are oolitic shallow-marine (non-volcanogenic) deposits formed around the rims of anoxic basins during high sea-level stands at locales starved of clastic sediment

PHOSPHORITES

generally form in much the same environmental niches as do banded iron formations, ironstones, and bedded manganese ores, namely along continental shelves and in shallow marginal marine settings such as lagoons and deltas Occur in extensive layers covering tens of thousands of square kilometers