trace elements in galena and sphalerite and their geochemical significance in distinguishing the...

Vol. 6 No. 2 GEOCHEMISTRY 1967

Trace Elements in Galena and Sphalerite and Their Geochemical Significance in Distinguishing the Genetic

Types of Pb-Zn Ore Deposits

ZHANG QIAN ( ~ ~ )

(Institute of Geochemistry, Academia Sinica)

Alm~aet

This paper deals with the trace elements Ag, Sh, Bi in galena and Fe, bin, Cd, Se, Te, a and In in

sphalerite from 60 Pb-Zn deposits in China and other countries. The contents of the selected trace elements

and their ratios show regular variations from one type of Pb-Zn deposits to another. These elements or their

ratios are plotted onto Pb--lnAg, lnSb-lnBi, lnGa-inln, Fe-Cd, Fe--Cd-Mn and Zn/Cd-Se/Tv--Ga/In

diagrams. On the basis of these diagrams, the deposits associated with magnmtism(type I), those associated

with volcanism(type II), the sedimentary-reformed deposits (type Ill) and sedimentary-metsmorphic

deposits(type IV) can be well distinguished. Types I and III have the definite fields in all the diagrams.

Types II and IV also have their own fields in lnGa-lnIn and Zn/Cd-Se/Te--Ga/In diagrams. The author

considers that these diagrams are applicable to distinguishing the genetic types of Pb-Zn deposits.

Introduetlon

A great wealth of mineralizing information may be developed from the trace elements in

galena and sphalerite. In the past twenty or thirty years, many geologists and geochemists t1-4I

studied the trace elements in Pb-Zn deposits, their existing forms and comprehensive utilization,

and classified the genetic types of Pb-Zn deposits in terms of trace elements or their ratios in

galena, sphalerite and pyrite. At present, Zn /Cd ratio in sphalerite and Co/Ni, S /Se and Se /Te

ratios in pyrite are widely adopted in the study of the genetic types of Pb-Zn deposits. In recent years, an approach of trace element diagrammatization has been used/Sj. No doubt, this is a further

step in the improvement of the approach, but none of the ratios or diagrams can be used to

perfectly distinguish the genetic types of Pb--Zn deposits. In the past years of practice both in the

laboratory and in the field, the author gathered a lot of data and pointed out that it is possible to

solve this problem if suitable trace elements are chosen. In this paper some trace elements in galena

and sphalerite from the selected Pb-Zn deposits are adopted. The purpose of this sdudy is to

distinguish the genetic types of Pb--Zn deposits on the basis of the data on trace element

geochemistry. Prof. Tu Gnangchi, director of the Institute of Geochemistry, Academia Sinica, has divided

the Pb--Zn deposits into 8 types t). This paper focuses on the geochemistry of trace elements in

those Pb-Zn deposits associated with magmatism and volcanism, and sedimentary-reformed,

sedimentary-metamorphic and migmatic PK-Zn deposits. Since epigenetic Pb-Zn deposits have

1) Tu Guangchi, 1960: The genetic classification of Pb--Zn deposits.

178 GEOCHEMISTRY VoL 6

some fnnilarities in trace element geochemistry with the sedimentary-reformed deposits, there is no need discussing them separately. The Qingchengzi Pb-Zn deposit is considered to be of both sedimentary-metamorphic and magmatic-hydmthermal Ol'i~l~ [6], 80 it is described as a special type of Pb-Zn deposits in this paper.

Tmee KImmmt Ounetm'imlm ef Calma

A variety of trace elements such as A& Sb, Bi, Cu, Hg, As, Cd, Se, Te, Ga, In and TI, are present in galena. Of so many trace elements, A& Sb, and Bi have been selected for the purpose of this study and their contents are fisted in Table L It is seen from Table 1 that the content of A K in galena varies from one type of Pb-Zn deposits to another, i.e., it is highest in the deposits associated with magmatism(generally > 1000 ppm, in some eases up to 5000 ppm), relatively low in the sedimentary-metamorphic, migmatic and deposits associated with ~zoleanism and the lowest values are found in sedimentary-reformed deposits (generally < 500 ppm). Shuai Dequan et al. t), and Huang Jingcong and Wang Yaping !~ have studied the existing forms of silver in galena and suggested that Ag exist mainly as micro-inclusions of silver minerals such as argentite, electrum, pyrargyrite, proustite and native silver, lsomorphous Ag occurs in trace amounts. Sb is relatively stable in the sedimentary-reformed deposits (generally > 1000 ppm). In contrast to Sb, Bi is lower than 10 ppm in galena from the sedimentary-reformed deposits, and more than 100

~m ,,¢ _c

%% 02 1 0 6 "~%

%%% 063031 30 O! 64 e 5 6 ~ 9 "~. ,,~, 023 COt9 /

"-. o n ".~-~.~2o

- - " .'. p ~ t s 7 ' t es~ "~ em .~41 J

. / 036 xxOlu . .I i - 028"

i i 046 ~" "" -r "" / O35/ / o37

• 45' I i • 47 e Ill I

/ I 040 39 /

! O / I • 50 / / I

I i I t / 85 86

o l e 2 0 3 0 4 o 5

I 87

Pb (%;

~ . L Pb-lnAg diagram of ~qdena (the symbols are the s~ue as in Table 1).

L The field of the deposits associated w/th magmatism; II. the field of the deposits associated with

volcanism; IlL the field of the sedim~tary-reformed deposits; 1. the deposits associated with malpnatism;

2. the deposits associated with volcanism; 3. the sedimentary-reformed deposits; 4. sedimentary-

metamorphosed and mi~matic deposits; 5. sedimentary-metamorphosed and ~ t i e hydrothermal

deposits.

I) Shuai Deq~n et al, 1982: Effila~ing forms of silver in ~vdem.

No.2 GEOCHEMISTRY 179

ppm(sometimes up to 10000 ppm) in galena from the depos i ts associated with magmatism and sedimentary-metamorphic deposits. Comparing Pb--Zn deposits of various types in the light of Pb / Ag, Pb / Sb, Pb / Bi and Sb / Bi ratios in galena, we will see that some of the ratios show regular variations, but most of them do not.

Shown in Figs. 1 and 2 are respectively the Pb-InAg and InSb-InBi diagrams of galena from the selected Pb--Zn de'posits.

Fig. 2.

.,Q

lnBi = 3. 5 " -* ~ 0 " 3 7 ' I

I \ I

3 8 1 Q I t I ~ I / "% O29 34 054 ~1 , , / 031 %'

35qL1019 / @ - J l ' - 0 4 0 055 % • - I I , o ~ ; o ( ' ~ \

o ~ / " l l~ ', u. / 3oeI f~; o~o o ~ ,,

I I I _ ] 1

04.7 . ' / \ o l

~ . j .s I % 0 3 / I '~

/ I % e~) s / I % I I I 1%'1 i

2 4 6 8 InBi

% %

012 ~

en2~a 10

lnSb-lnBi diagram of galena (the explanations are the same as in Fig. 1, the same in the following figures.

In Fig.I, the deposits associated with magnmtism, those with volcanism and the sedimentary- reformed deposits cart be respectively plotted into fields I, II and III. But field II overlaps fields I and III. Their locations depend on Ag contents. The Xitieshan deposit falls into the overlapping part of fields I and II, while the Wubu and Kuroko deposits into the overlapping part of fields II and III; some sedimentary-reformed deposits such as Fankou and Yindongzi into field I. It is probably the regional source of silver (probably related to volcanism) that resulted in high Ag contents of these two deposits. The Taolin deposit occurs in the contact zone between the Mnfushan granite and argillo-arenaceous formations of the Banxi system. The ore bodies are distributed along fault zones as Veins. It is considered as a rnagumtic-hydrothermal-filling Pb-Zn deposit. Therefore, it is designated to type I in Table 1, but falls into field III in Fig. 1. This indicates that Ag content in galena from Taolin is similar to that in galena from the sedimentary- reformed deposits. The sedimentary-metamorphic and mignmtic deposits are relatively scattered in Fig. 1. Pb-Zn deposits of this type have a much higher Ag content in galena, and therefore they fall near the deposits associated with magmatism. Ag content in galena from the Qingchengzi deposit is similar to that in galena from the type-I deposits, so the Qingchengzi deposit falls into field I.

In Fig.2, the deposits associated with magumtism can be distinguished from the sedimentary- reformed deposits. The former falls into the field with lnBi > 3.5 and the latter into the field with lnBi < 3.5. No sufficient information has been obtained on the deposits associated with volcanism. The Xitieshan and Wubu deposits are in field III and the Kuroko deposits in field I. They are generally distributed along the borders of fields I and III. All the sedimentary-metamorphic and migumtic deposits fall into field I. This fact indicates that galena from these deposits contain

Tab

le 1

. T

he e

onte

ntJ

of t

raee

ele

men

ts i

n ga

lena

and

,pl

uder

ite

from

the

*el

ecte

d Pb

--Z

n de

pedt

* (p

lpm

)

Dep

osit

ty

pe

.7 i

Dep

osit

nam

e] N

o.

Fuzi

chon

g

Xia

shan

Hua

nren

Shui

kous

han

Hua

ngsh

apin

g

Don

gpo

Hen

gsha

nlin

g

Cha

isha

n

Qib

aosh

an

Tao]

]n

Ave

rage

of

22 d

epos

its

in H

unan

Prov

.

Mid

dle-

low

er

reac

hes

of

the

Tan

gtzi

Riv

er

Don

gxia

ng

Yan

gbei

Don

ggan

gsha

n

Lam

e

Dab

aosh

an

Xia

oxili

n

Bei

ya

Xia

ngku

ang

Gal

ena

Spha

leri

te

Pb(%

) [

Ag

[ Sb

[

Bi

[Zn(

%)

[ Fe

(%)

I M

n(%

) C

d(%

)

0.53

0.33

0.35

0.21

.o_

O~


¢,]. ~. b ~

oea

m .mu~oloA ql.u~

p~]~oos~ ~!soda~i "II

-~~

g.

~ d

sl!e~dop pomao3~-.~muomq ~ "III

~ d d d d d. o i

d ~ d d ~ d o d d d

T~

de

1. (

Con

tinue

d)

L~

o

Dep

osit

D

epos

it n

ame

type

Mis

siss

ippi

va

lley

-typ

e

Car

bona

te-

"~

type

in

SSSR

e~

"~

Mid

dle

Asi

an

Rah

ovo

Nig

eria

.~

Syng

enet

ic

type

(B

rita

in)

Com

e

Bru

ce

Bin

nata

l

Ave

rage

Xiy

upl

Wu

ao

Cha

nh

Tuo

gou

.~

Xia

nren

zui

Hon

gtou

shan

"~

Bro

ken

Hill

Ave

rage

V.

Qin

gche

ngzi

Not

e:

No.

45

Gal

ena

Pb

(%)

Ag

Sb

86.3

18

4

Bi

Zn(

%)

Sph

aler

ite

46

47

48

49

86.1

84

70

i

50

86

10

8

51

52

53

1200

20

0

54

86.1

5 43

6 11

63

3 15

13

6O

Fe(

%)

Mn

(%)

Cd(

%)

Se

1.53

0.

6O4

0.4

55

86.4

13

40

755

583

56

84.9

53

20

8.6

1110

0

57

86.5

51

5 43

2 45

58

59

6O

61

62

86.6

61

8 10

10

135

63

85.5

19

48

551

2966

58.3

5

0.03

0.

007

0.39

0.35

0.

012

0.14

4

0.54

0.

002

0.35

1.1

0.03

0.

34 -"

1.17

0.

03

0.35

8.84

0.

29

0.34

5.4

0.18

0.

41

3.79

0,

24

0.42

5

8.35

0.

195

15

1.1

0.21

8.3

0.45

0.

35

64

86.3

5 13

54

1800

4.

25

60.1

0.

42

Typ

e V

ref

ers

to t

hose

dep

osit

s of

sed

imen

tary

-, m

etam

orph

ic-m

agm

atic

hyd

roth

erm

al o

rigi

n.

Te

0.24

0.

2 1

2.04

17 0.2

0.7

41 6

2.19

1 0.01

0.1

7 0.37

0.1

Ga

119 4

14o 50

170 96

12.9

71.3

4 2.5

12

84

57

12.5

31.9

104

In 1.

6

0.2

2 17 1 96.3

11.4

1414

14o

186 1 14

17.5

351 13

.5

H

pc g m

,.4

.,e


higher Bi. The Huangshaping, Chaishan and Beiya deposits fall into field Ill. The Fankou deposit which is believed to be of sedimentary-reformed origin is located in field I. This is due to the difference in Bi content for galena from these deposits. Galena from the Qingebengzi deposit is characterised as being high in Sb content but low in Bi content, so the deposit falls into field IlL This reflects its sedimentary features.

As can be seen from the above, it is of some practical significance to use Pb--InAg and InSb-- InBi diagrams of galena t'o distinguish the genetic types of Pb--Zn deposits. For example, the deposits associated with magmatism can be well distinguished from the sedimentary-reformed deposits in terms of the diagrams, the former falls into field I and the latter into field HI. Most deposits of these two types can be plotted into the corresponding fields. The field of the deposits associated with volcanism lies between fields I and III, and partly overlaps the two fields. The sedimentary-metamorphic and mignmtic deposits have no independent fields in the two diagrams. They fall mainly into field I. Deposits of this type were formed under high temperature-high pressure conditions, or from metamorphic or ~ t i c - h y d r o t h e r m a l solutions. Therefore, their trace elements (Ag, Sb, Bi) in galena are similar to those found in deposits associated with magmatism. The Qingchengzi, Taolin and Chaishan deposits have no definite locations in the diagrams. This may be ascribed to diverse sources of ore-forming elements in these deposits.

Moreover, the author once studied other trace elements such as Se, Te, Cd, T1 and Hg in galena and the related Ag-Sb-Bi and Pb--InT1 diagrams, and found that the geneti~ types of Pb- Zn deposits could not be distinguished in terms of the diagrams.

Trace Element Clmractedsti~ of Splmle~te

In this paper Fe, Mn, Cd, Se, Te, Ga and In in sphalerite are selected and their contents are presented in Table 1. Tl~e contents of Cd, Se, Te, Ga and In in sphalerite from various types of Pb- Zn deposits are highly variable, even in the same type of deposits. However, some regularities may be followed as described below:

(1) Zn / Cd ratios: < 200 in the deposits associated with magraatism and in the sedimentary- metamorphic deposits, > 200 in the sedimentary-reformed deposits, and > 200 • < 200 in the deposits associated with volcanism.

(2) Ga / In ratios: Generally Ga is lower than In, and Ga/In is < ] in the deposits associated with magnmtism and in the sedimentary-metamorphic deposits~ Ga is higher than In and Ga / In is > 1 in the sedimentary-reformed deposits. The values for the deposits associated with volcanism vary between < 1 and > I.

(3) Se / Te ratios: Generally Se is higher than Te, and Se / Te > ] in the deposits associated with magnmtism and volcanism, and in the sedimentary-metamorphic deposits. The values for the sedimentary-reformed deposits are opposite to those for the other types of deposits.

Fe(>6%) and Mn(0. x%) contents of sphalerite from the deposits associated with magmatism and the sedimentary-metamorphic deposits are higher than those from the other types of deposits. These values for the sedimentary-reformed deposits (Fe <3%, Mn about 0.O x - 0.00 x %) are I - -2 orders of magnitude lower than those for the deposits associated with magmatism.

Fe, Cd, Ga, In, Sb and Bi are chalcophi]e elements, which are similar to Znin ionic radius. Therefore, these elements frequently isomorphously replace Zn in sphalerite. Se and Te are

184 G E O C H E M I S T R Y Vol. 6

sulphophile elements, and thus they frequently replace sulfur in sulfides. The extent of substitution depends on concentration; temperature, pressure and pH. Thus these elements show regular distributions in the various types of Pb-Zn deposits. This is the theoretical basis for distinguishing the genetic types of Pb-Zn deposits in the light of trace element characteristics and their diagrams.

In this paper lnGa-lnIn, Fe--Cd, Fe-Cd-Mn and Zn/Cd-Sefre-Ga/In diagrams are plotted on the basis of the available trace element data.

laGs-lain diagram of sphalerite

Fig. 3 shows the lnGa-lnIndiagram of sphalerite from the selected Pb-Zn deposits. In terms of Fig. 3, we can successfully distinguish the deposits associated with magmatism from the sedimentary-reformed deposits. Pb--Zn deposits of these two types are distinctly separated by the Ga / In = 1lime. The former is in field I where Ga / In is < 1 and the latter in field III where Ga / In is > 1. The Taolin and Hengshanling deposits that are considered to be of magmatic-hydrothermal origin are plotted into field III. Ga is higher than In in sphalerite from the two deposits, and Ga/In is similar to that in the sedimentary-reformed deposits. This shows that in the two deposits the source of Ga and In is related to sedimentation. The deposits associated with volcanism are distributed on both sides of the Ga/In = 1 line. It implies that PI>-Zn deposits such as the Xiaotieshan, Wubu and Yinshan deposits that are located on one side of the Ga / In < I line can be designated to the magmatic-hydrothermal type and Pb-Zn deposits such as the Xitieshan that are located on the other side can be assigned to the volcano-sedimentary type. The Kuroko deposits in Japan and some stratiform PI>--Zn ~eposits in volcanic rocks in Uzbekstan, SSSR Is] are also of volcano--sedimentary origin. This classification is consistent with field observations. Some sedimentary-metamorphic deposits such as the Xishan and Xianrenzui all fall into field III, but migmatic deposits such as the Wubu, Chanli and Broken Hill fall into field I. This indicates that in these deposits the re-assemblage and re-distribution of ore-forming elements took place under high temperature-high pressure and partial re-melting conditions. Therefore, these deposits show similar features to those of the deposits associated with magmatism. Although the Hongtoushan deposit has undergone metamorphism and migmatization, its primary ore-forming materials are

8

G a / [ n > 1 ~" - -- -- -- ~ G a / I n = 1

. . / S 031 '~'% /

,,"~9 ~7 olo x~._7<e a./ l .<z

/ _ . . , , . " 0 6 0 / 11 m , ~ O I 7 % 4 / e ~ " e4a L 1 2 o - ~ x

I 1 .,~ 0 6 3 037 / II / 30 . ~ a I

.Ja3K 0 2 9 / / 024 , , , 1019 I I aa L~a5 t -m.~" 922em I

032 07 • ~ / 26 ,,.Do ot.,~ I o3,i ~ ~ ,,'.o ~ ( + o. 8 011

~-.,/. ~,.-'O lo 4 56 ! / 015 • I " " + " '

/ O • 57 " 30 I

/ / I 018 / I +' I I 0 1 I t , . I r J

=2 0 2 4 6 8

la in

Fig. 3. l n G a - l n I n d i a g r a m o f sphaler i te .


believed to have come from submarine volcanic eructations [9-1ol and its composition has not yet been affected by later processes. So it still shows the features of volcano-hydrothermal origin. The Qingchengzi deposit that falls into field III shows the features of sedimentary origin.

Fe-Cd .and Fe--Cd-Mn diagrams of sphalerite

In Figs, 4 and 5, fields I and III can be distinctly separated. In Fig. 4 where Fe = 5% is taken as the boundary line, the deposits associated with magmatism fall into field I(Fe > 5%) while the sedimentary-reformed deposits in field III(Fe < 5%). The Qixiashan deposit fails into field I as shown in Fig. 5. This may be related to its high Mn content. The data points for the deposits

0.8

0.6 J35 07

036

o.

® - o o e o34 28 425326 O41

0 . 2 '

051 010 132

0 I 2

Fe = 5% \

\

\ % \ \

llI %

e3o f

I !

®31 / /

/ /

t" I 4

Fig. 4.

018 / f

f f

/

I / o0 o t I [ 013 o16

57 I • I oll

j 63 0 23 !

~ 2 k 0 17 ~ o ~.o

04 O ~ 25e \ o9

\ 021 \

\ %

%. I I 6 8

Fe (%)

Fe-Cd diagram of sphalerite.

Gd × 10

/ o~0 .~ ® . ,,, \ / __.-' \ / . . . . .sT ! I ~ o 14- ' I \

/ . oOOo. o. ,, \

F~. 5. Fe-Cd-Mn diagram of spt~lefite.

10

! I 10 12 14

186 GEOCHEMISTRY Vol. 6

associated with volcanism are randomly scattered in the two diagrams. The sedimentary- metamorphic and mignmtic deposits fall into field I.

Zn / Cd-Se / Te--Ga / In diagram of sphalerite

Fig. 6 is the Zn / Cd-Se / Te-Ga / In diagram of sphalerite from the selected Pb-Zn deposits. In this figure, the deposits associated with magrnatism and volcanism are plotted into field I. All the sedimentary-reformed deposits are plotted into field HI with all the points highly clustered. The sedimentary-metamorphic and ' migmatic deposits also fall into an independent field (field IV). The Wuao, Tuogou and Chanli deposits fall into this field, too. The Hongtoushan deposit is in field I, suggesting a volcano-hydrothermal source for its ore-forming materials. The fact that the Qingchengzi deposit falls into field IV in Fig. 6 indicates that it is of sedimentary-metamorphic origin. From the location of the Taolin deposit in Fig. 6, it is evident that the deposit is of sedimentary-reformed origin.

Zn/Cd (10 -1) V !

V 2 e 3 m4

~ 5

& 6 1"17

S e ~ / t -" "~ 37 ~. Ga/In

Fig. 6. Z n / C d - S e / T e - G a / l n diagram of sphalerite.

L Xiashan; 2. deposits in volcanic rocks of Uzbokstan, SSSR; 3. Fankou; 4. deposits in carbonate rocks

of Uzbekstan, SSSR; 5. Wuao: 6. Chanli; 7. Qingchengzi.

The contents of Zn, Cd, Se, Te, Ga and In in sphalerite from the selected Pb-Zn deposits are given.in Table 2. Plotting the data for these trace elements onto Fig. 6, we see that different types of Pb-Zn deposits fall into different fields, i.e., the Xiashan deposit into field I, the deposits in volcanic rocks of Uzbekstan into field II, the Fankou deposit and the deposits in carbonate rocks of U zbekstan into field III, and the Wuao and Chanli deposits into field IV. The data points for the Qingchengzi deposit are very scattered, one in field IV, two in field III and another point near field I. All this is sufficient to show that the formation of this deposit has such to do with sedimentation and metamorphism and magmatic-hydrothermal reworking.

Diseussion and Conelusions

As stated above, such trace elements as Ag, Sb, Bi, Fe, Mn, Cd, Se, Te, Ga and In in galena


Talde 2. ~ ¢om~t~ of ~ elemeats in qdudedte from several &imd~

Deposit name Sample No. Zn(%) Cd(%) Se Te Ga In

83FC-I-2 0.33 17 6 2 80 Xiashan

83FC-25 0.32 15 3.4 1.3 87

82ZI~-3 0.43 0.2 0.01 2.1 9.6 Chanli

82ZL-4 0.39 0.46 0.01 2.9 270

Wnao

82WY-B 0.37 22 0.18 3.5 170

82WY-13 0.14 6.3 0.01 5 5.3

82WY-25 0.30 36 0.6 4.5 4.5

82WY-25--4 0.41 29 I 4.6 310

82WY-28 0.41 1.4 0.14 4.2 41

82WY-31 0.39 6.6 0.7 1.7 390

Fankou

1 59.64 0.27 4 1 190 10

2 55.97 0.19 5 1 380 10

3 62.27 0.16 4 I 540 I0

4 59.82 0.2 4 1 280 I0

5 61.61 0.16 4 1 340 I0

6 58.43 0.27 4 1 540 10

7 61.59 0.17 4 1 430 7

Qingchengzi

1 0.19 21 ~ ~ 61

2 0.I0 5 I 29 1

3 0.~ I 1 ~ 1

Deposits in 1 0.13 0.8 2.6 1.3 0.2

carbonate rocks 2 0.12 0.8 1 1.2 0.2

of Uzbekstan 3 0.16 0.2 1 4 0.2

Deposits in 1 0.3 58 5 52 14

volcanic rocks 2 0.32 220 73 9 10.5

of Uzbokstsn 3 0.32 102 15.2 8.5 100

and sphalerite, except for A 8 which occurs mainly as micro-inclusions of independent minerals

(substantially argentite) in galena, can isomorphously replace Pb, Zn and S in sulfide minerals.

Their contents depend on the amount of the host elements replaced and are controlled by

mineralization conditions, sources of ore-forming elements, temperature, pressure, etc. Different

genetic types of P b - Z n deposits were formed under different mineralization conditions and hence

they have different contents of trace elements. This tendency is the theoretical basis for


Fig. 7.

2O0O

031 1600

"i ~ 1 2 0 0

<

800

056

0:1

0 0 4 55

0 1

e 2

e 3

o 4 ® 25

05 • 5 20£)

® 24

o32 41o 026

035

I , I I I ,

150 200 250 300 350 7" (°C)

015

Relationship between Ag content in galena and ore--forming temperature (from Yu Cimei, 1980, 1984, 1985).

L Deposits associated with magmatism; 2. deposits associated with volcanism; 3. sedimentary-reformed

deposits; 4. sedimentary--metamorphosed and migmatic deposits; 5. sedimentary-metamorphosed and

magraatic hydrothermal deposits.

distinguishing the genetic types of Pb:-Zn deposits in the light of trace element geochemistry. The influence of geological conditions on trace elements in galena and sphalerite is mainly reflected in the regular variation of trace elements from one type of Pb--Zn deposits to another. For example, the deposits associated with magmatism are enriched in Ag, Bi, Fe, Mn and In, while the sedimentary-reformed deposits in Sb, Ga, etc. The contents of trace elements in some deposits are related to their regional sources. For example, the sedimentary-reformed deposits are generally low in Ag, but the Yindongzi and Fankou deposits contain as high as 1000-ppm Ag, indicating a volcanic source of silver. Gaiena from the Wuao and Xiashan deposits contain more than ] % Bi. High ground levels of Bi in this area is a possible explanation.

The temperature is also an important factor affecting trace elements. For example, sphalerite from the sedimentary-reformed deposits contains high Ga, which may be related to exodiagenesis. Since ore-forming elements in the Wuao and Tuogou deposits were derived from sedimentary formations, Ga should he higher than In. Nevertheless, with increasing temperature when the deposits underwent metamorphism, Ga decreased and In became higher than Ga. Fig. 7 shows the

relationship between Ag content in galena from the selected deposits and ore-forming

temperature. Apparently, with the rise of ore-forming temperature, Ag content in galena also tends to increase, suggesting that Ag content is a linear function of temperature. The Fankou

deposit are an exception. In short, if we select suitable trace elements in galena and sphalerite as variables and have

them diagrammatized, we can distinguish the genetic types of Pb-Zn deposits successfully. (1) The locations of various types of Pb-Zn deposits in the diagrams indicate that the fields

into which the deposits fall are in good agreement with the actual situation. The data points for the


deposits associated with magmatism and the sedimentary-reformed deposi~ almost fall into their own fields. The Use of these diagrams makes it possible to distinguish these'two types of Pb-Zn deposits.

(2) The deposits associated with volcanism include volcano-hydrothermal and voleano- sedimentary deposits. The ore-forming materials of the former came mainly from magma (e.g. the Xiaotieshan, Yinshan Wubu, etc.) and those of the latter came not only from magma but also from seawater (e.g. the Xitieshan and Kuroko). Therefore, the field into which Pb-Zn deposits of this type fall always overlaps with fields I and lII (see Figs. 1, 2, 3 and 6). Generally speaking, the volcano-hydrothermal-fdling deposits fall near the deposits associated with magmatism and the volcano-sedimentary deposits near the sedimentary-reformed deposits. In some deposits (e.g. the Wubu), their ore-forming materials came from volcanic and other sources. Therefore, there are no definite locations for these deposits in the diagrams. In Figs.1 and 2 they fall into the field overlapping that of the sedimentary-reformed deposits, but in Fig.3 they fall into the field overlapping that of the magmatic-hydrothermal deposits.

(3) The sedimentary-metamorphic and migmatic deposits mostly fall into field I. Only in Fig.6 can they have a definite field. In fact, Pb-Zn deposits of this type were formed under the conditions of high-grade metamorphism or/and migmatization. Due to high temperature and pressure, their compositions have changed, and thus the deposits show such trace element features as those of the deposits associated with magm~itism. The Hongtoushan deposit underwent migmati~tion, but its ore-forming elements came from submarine volcanic eructations, and no addition or loss took place in the subsequent processes of metamorphism and migmatization. Therefore, its trace element features are similar to those of the deposits associated with volcanism, but quite different from those of the sedimentary-metamorphic and migmatic deposits. This indicates that the sedimentary-metamorphic deposits have two district sources of ore-forming elements: one is sedimentation and the other is volcanism. In some low-grade (green schist facies) metamorphic deposits such as the Xiaotieshan, Xitieshan and Yindongzi. Their trace element assemblages have not been significantly affected by light metamorphism and therefore the original mineralization features are still recognizable.

(4) The Qingchengzi deposit is one of the sedimentary-metamorphie-nmgmatie- hydrothermal deposits. Its indefinite location in the diagrams just provides evidence suggesting its polygenesis and multiple source of ore-forming elements.

(5) According to Wang Yumin [111 and Ding Tiping 1~, the Taolin deposit is a typical magmatie-hydrothermal deposit. Zheng Zhiyi et al. consider that it was formed by precipitation from uadose waters. Since it always falls into field III in all the diagrams, it should be designated to the sedimentary-reformed deposits. Wang Wenbin 3J and Yin Hanhui tlzl hold that the Fuzichong and Dabaoshan deposits are of sedimentary-magmatic hydrothermal origin. But these deposits have defmite locations in the diagrams. That is to say, they always fall into field I. It is postulated that both deposits almost have nothing to do with sedimentation. In addition, some deposits in the Dongpo ore field (Hunan Province) such as the Chaishan and H~ngshanling have no definite

1) Ding Tiping, 1982: A study of S, O, H and Pb isotopes of the Taolln Pb--Zn deposit. 2) Zheng Zhiyi at al., 1982: On the genetic types of Pb--Zn deposits in China. 3) Wang Wenbin et al., 1982: The genetic classification of Pb-Zn deposits in China and a discussion of some geological

questions.


locations in the diagrams. It is deduced that the host rocks of sedimentary origin in this district

seem to be one of the contributors of ore-forming elements. (6) If the content of a certain trace element or the ratio of any one trace element to another

shows reg~,lnr variations from one type of Pb-Zn deposits to another, diagrams can be plotted to distinguish their genetic types. Hence it seems that the diagrams of sphalerite are more applicable than those of galena. Pb--lnAg, lnGa-lnln, Fe-Cd and Zn / Cd - Se / Te - Ga / I n diagrams are regarded as the most ideal ones for distinguishing the genetic types of Pb-Zn deposits.

In short, research on trace element geochemistry of galena and sphalerite is an important

approach to distinguishing the genetic types of Pb-Zn deposits. However, satisfactory results

could not be achieved uuless it is combined with other approaches.

A e h u o ~ , s

In this paper such information is provided by my colleagues from the geological teams and

mines concerned. Wang Xiuzhang and Zhang Baogui reviewed the manuscript. Chen Xiuyun and Lti Peiqin et al. provided a lot of analytical data. Field investigations were supported by many

mines concerned. The author wishes to thank them all.

l lefereu

[ 1 ] Jonasson, I.R. and Sangster, D.F., Geol. surv. Canada, 78-1B(1978), 195--201.

[ 2 ] Bralia, A. et al., Mineral Deposita, 14(1979), 353--374. [3 ] Zhao Zhenhna, <<Geochem/stry>>, ShA-ghai Science and Technology Press, Sl~n~mfi, (1984), 190--267.

[4] Song Xuexin, Rock and Mineral Analysis, 3, 1(1982), 37--44. [ 5 ] Tong Qi~nming~ Rock and Mineral Analysis, 3, 4(1954), 322--330. [ 6 ] Zhan~ Quisheng et al., Geology and Minerogenesis of the Early Premmbtian in China, People's Publishing House

of Jilin Province, 1984, 265--298. [ 7 ] Huang Jingcong and Wang Yaping, Acta Mineralogica Sinica, 2(1984), 173--178. [ 8 ] Pankratiev, P.V. and Mihailova, U.V., The Stratiform Ore Formations of Pb-Zn Deposits in Uzbekstan, SSSR,

Publishing House of the Uzbekstan Republic, 1981, 26--84 and 195--148.

[ 9 ] Guo Shiqin, Rock and Mineral Analysis, 3, 4(1964), 330--336. [10] Cheng Yuqi et al., A Collection of Academic Papers on Geology for International Exchange presented to the

27th International Geological Congress, 4(1985), 311--320.

[11"] Wang y,,mln, Geol. of Mineral Deposits, 1(1983), 21--29. [12] Tu Guangchi et al., << Geochemistry of the Strata-bound Deposits in China>>, 1(1984), Science Press, Beijing,

20--24.

trace elements in galena and sphalerite and their geochemical significance in distinguishing the...

Documents