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Geology, petrology, geochemistry and...

Chai, Gang.

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Geology, petrology, geochemistry and nickel-copper-PGE mineralization of the Jinchuan intrusion, northwest China.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Geology, petrology, geochemistry and nickel-copper-PGE mineralization of the Jinchuan intrusion, northwest China./
Author:	Chai, Gang.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 1992,
Description:	336 p.
Notes:	Source: Dissertation Abstracts International, Volume: 53-12, Section: B, page: 6185.
Contained By:	Dissertation Abstracts International53-12B.
Subject:	Geology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=NN73865
ISBN:	9780315738652

Geology, petrology, geochemistry and nickel-copper-PGE mineralization of the Jinchuan intrusion, northwest China.
Chai, Gang.

Geology, petrology, geochemistry and nickel-copper-PGE mineralization of the Jinchuan intrusion, northwest China. - Ann Arbor : ProQuest Dissertations & Theses, 1992 - 336 p.

Source: Dissertation Abstracts International, Volume: 53-12, Section: B, page: 6185.

Thesis (Ph.D.)--University of Toronto (Canada), 1992.

The Jinchuan intrusion is a northwest striking ultramafic dyke-like body located at the southwest margin of the Sino-Korea platform. It is about 6 km long and 350 m wide, and is the host to the second largest Ni-Cu deposit, which contains 500 million tones of ore grading 1.2 wt% Ni and 0.7 wt% Cu.

ISBN: 9780315738652Subjects--Topical Terms:

516570
Geology.

Geology, petrology, geochemistry and nickel-copper-PGE mineralization of the Jinchuan intrusion, northwest China.
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245 1 0 $a Geology, petrology, geochemistry and nickel-copper-PGE mineralization of the Jinchuan intrusion, northwest China.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 1992
300 $a 336 p.
500 $a Source: Dissertation Abstracts International, Volume: 53-12, Section: B, page: 6185.
502 $a Thesis (Ph.D.)--University of Toronto (Canada), 1992.
520 $a The Jinchuan intrusion is a northwest striking ultramafic dyke-like body located at the southwest margin of the Sino-Korea platform. It is about 6 km long and 350 m wide, and is the host to the second largest Ni-Cu deposit, which contains 500 million tones of ore grading 1.2 wt% Ni and 0.7 wt% Cu.
520 $a The intrusion comprises three magma subchambers: the west, west-central and east. The western two subchambers are narrow and tabular in shape. A lateral zonation of rock types is present, with dunite at the core, grading through lherzolite to olivine pyroxenite at the margins. The sulfide mineralization is also zoned, with Ni, Cu and PGE increasing from the margins towards the centre. The ores have high PGE contents, corresponding to about 20 ppm total PGE in 100% sulfide. The eastern subchamber is Y-shaped and is characterized by vertical layering in which dunite occurs at the base and grades upwards into lherzolite, plagioclase lherzolite, and then lherzolite again at the top. Geochemical analyses show that Ni, Cu and PGE, as well as S in this subchamber, decrease from the base upwards. However, when normalized to 100% sulfide, the PGE increase upwards but Ni and Cu are more or less constant. Sulfide ores in this subchamber contain $<$0.6 ppm total PGE in 100% sulfide.
520 $a Major, trace and rare earth elements analyses show that the intrusive rocks are MgO-rich, with the majority containing $>$35 wt% on an anhydrous basis. Linear negative correlations are observed between MgO and most other elements, with the exception of a few mobile elements such as $\rm Na\sb2O,$ $\rm K\sb2O,$ Sr and Rb; this suggests that the rocks are essentially mixture of cumulus olivine and primary magma. The cumulus olivine has forsterite contents mainly between 83-85%, which corresponds to calculated MgO/(MgO + FeO) ratio of the primary magma of 0.64, which, in turn, indicates an MgO content for this magma of about 12 weight percent.
520 $a The ore samples studied have an average Ni/Cu ratio of 2 and (Pt + Pd)/(Ru + Ir + Os) ratios of between 5 and 30, with most values falling in a range of 10-15. The chondrite normalized PGE distribution patterns are always Pt, Pd and Au enriched, and Os, Ir and Ru depleted. This type of pattern is a typical feature of sulfide deposits that are related to gabbroic magma.
520 $a It is concluded that: (1) the intrusion represents the ultramafic cumulates of a high-MgO basaltic magma; (2) the western part of the Jinchuan intrusion is the major conduit of pure original magma and the rocks in this part have formed as a result of a process of flow differentiation, whereas the eastern part represents a higher level in the magma chamber where crystallization occurred in response to magma convection with periodic replenishment; (3) PGE concentration is the result of segregation of a sulfide liquid that had equilibrated with the silicate magma. The different PGE contents of the sulfide from the western and eastern parts of the intrusion suggest that two silicate magmas were involved. The PGE-rich liquid equilibrated with a relatively primitive magma whereas the PGE-poor sulfide liquid equilibrated with a magma already PGE-depleted by prior sulfide segregation.
590 $a School code: 0779.
650 4 $a Geology. $3 516570
650 4 $a Geochemistry. $3 539092
690 $a 0372
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710 2 $a University of Toronto (Canada). $3 1017674
773 0 $t Dissertation Abstracts International $g 53-12B.
790 $a 0779
791 $a Ph.D.
792 $a 1992
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=NN73865