7/21/2019 AbstractStratiform Deposits (Sulphide, Oxide Deposits) of Sedimentary and Volcanic Environment

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Stratiform Deposits (Sulphide, Oxide Deposits) of Sedimentary and

Volcanic Environment

By

MUBS!"# $!%

U&"# S'"

#MUS! ME!BOOB

!UM #SOO

BS EOO* V""

Department of Earth and Environmental Sciences

Bahria University, "slama+ad

-./

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7/21/2019 AbstractStratiform Deposits (Sulphide, Oxide Deposits) of Sedimentary and Volcanic Environment

http://slidepdf.com/reader/full/abstractstratiform-deposits-sulphide-oxide-deposits-of-sedimentary-and-volcanic 2/4

ABSTRACT

  In stratiform deposits, there is a predominance of stratied bodies

that are conformable with the enclosing rocks. The ores in these bodies have

simplemineral compositions determined by the dissemination of copper, zinc,

and lead suldes and the accompanying minerals in one or more strata of

the orebearing rocks. Stratiform deposits are generally of large size, cover a

broad area, and form vast ore regions or provinces for e!ample, the

"ississippi#alley lead and zinc deposits$.

Several hypotheses have been advanced on the origin of stratiform deposits.

In the view of such geologists as %. &akharov and '. Satpaev of the (SS),*.

+ehre of the (S, and *. -avidson of reat +ritain, stratiform deposits are of 

hydrothermal origin. This hypothesis, however, is contradicted by

theabsence of magmatic rocks in the areas where the stratiform deposits are

found. nother hypothesis, whose adherents include #. /opov and #.-omarev

of the (SS) and 0. ruszczyk of /oland, regards stratiform deposits as

sedimentary formations that arose from marine sediments on thebottoms of

ancient seas together with the enclosing rock strata. This view is

contradicted by the presence of crosscutting ore veins along with thebedded

ore bodies.

0ydrothermal mineral deposits are the products of crustal geochemical

processes that e!tract metals from source regions and concentrate them at

depositional sites. These processes and the regions in which they occur

constitute 2mineral systems2. /rocesses that occur within source regions

dene the characteristics e.g. temperature, pressure, p0, salinity, redo!,

sulphur content$ of hydrothermal 3uid s, which, in turn, determine the metal

carrying capacity of the 3uid. "ineral deposits that contain *u, &n, /b, g

and4or u can be classied into three general groupings based on metal

assemblages5 I$ &n/bg6u , 7$ *u6u , and 8$ u6g. In terms of zinc,

lead, and silver lnetal endowment, the /roterozoic sedimentary basins of

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7/21/2019 AbstractStratiform Deposits (Sulphide, Oxide Deposits) of Sedimentary and Volcanic Environment

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northern ustralia rank number one in the world. The "t. Isa"crthur basin

system hosts ve supergiant, stratiform, sedimentary rockhosted &n/bg

deposits "crthur )iver, *entury, "t. Isa, 0ilton, and eorge 9isher$ and

one supergiant stratabound g/b&n deposit *annington$. These

superbasins consist of units deposited during tlwee nested cycles of

deposition and occurred in the period from 1:;; to 1<:; "a. The cycles took

place in response to fareld e!tension and subsidence associated with a

ma=or northward dipping subduction zone in central ustralia. ll ma=or

stratiform zincdominant deposits occur within rocks of the sag phase of the

youngest Isa superbasin, which was deposited between 1>?; and 1<:; "a.

#olcanicassociated massive sulde #"S$ deposits range from lensshaped to sheetlike bodies of suldemineralrich rock spatially associated

with volcanic rocks ranging in composition from basalt to rhyolite. #"S

deposits can be divided into three general categories. Cyprus-type deposits

tend to be small, mediumgrade deposits rich in copper and zinc. They are

generally lens or mound shaped accumulations of massive pyrite developed

in ophioliterelated, e!trusive basalt se@uences. They are typically underlain

by copperrich AstringerzonesA composed of anastomosing @uartzsulde

mineral veins in e!tensively chloritized basalt. Kuroko deposits are

typically developed in intermediate to felsic volcanic rock and are generally

interpreted to have formed in e!tensional environments associated with arc

volcanism. They are commonly high grade and can be very large. )elative to

*yprustype deposits, they generally have much higher contents of zinc,

lead, silver, and antimony, which re3ect the composition of their felsic

volcanic host rocks. They also have moundlike morphology and the

abundance of coarse clastic sulde minerals within many of these deposits

attests to a moderately high energy, sea3oor depositional setting. 'uroko

type deposits also tend to be underlain by copperrich stringer zones and

commonly have well developed geochemical zonation with progressive zinc,

lead, and silver enrichment both vertically and laterally away from vent

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7/21/2019 AbstractStratiform Deposits (Sulphide, Oxide Deposits) of Sedimentary and Volcanic Environment

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centers. Besshi-type deposit s are present in mi!ed volcanicsedimentary

environments. -eposits of this type are commonly hosted by turbidites that

have been intruded by basaltic sills. These deposits are typically copperrich

and contain small abundances of lead and other lithophile elements. In

contrast to other volcanichosted deposits, many +esshitype deposits form

thin, laterally e!tensive sheets of pyrrhotite and or$ pyriterich massive

sulde rockB however, the characteristics of +esshitype deposits vary

considerably. Slack 1CC8$ presents an e!panded denition of +esshitype

deposits that includes deposits such as those in the -ucktown, Tenn., district

and the large Dindy *raggy deposit in +ritish *olumbia.

E