Weathering Sources in the Kaoping River Catchment, Southwestern Taiwan: Insights From Major and

Trace Elements, Sr Isotopes and Rare Earth Elements

C.-F. You, K.-F. Huang, C.-H. Chung and R.-M. Wang

Department of Earth SciencesAlso at Earth Dynamic System Research Center

National Cheng Kung University 

Ching et al., 2007 Liu et al., 2007

Outlines

• Sr isotopes

Non-conventional high precision Sr isotopic measurement

• Major and trace elements• REEs

Strontium Isotopes:

84Sr (0.56 %) 86Sr (9.86 %)

87Sr (6.99 %) 88Sr (82.54 %)

87Rb 87Sr＋ β -＋ anti-neutrino＋ energy

(t1/2＝ 4.88× 1010years)

Geological Applications:

1. Geo-chronometer:

Rb-Sr dating

Seawater curve

2. 87Sr/86Sr Tracer:

a. River water --- weathering process

b. Sediments--- provenance and transportatio

n

c. Biogenic carbonate---seawater evolution

3. Environmental proxy

SST or SSS

Sr Isotopic Composition of Earth Systems

M id -o c e a n rid g eHyd ro h e rm a l c irc u la tio n

Sr/ Sr= 0 .7 0 3 58 7 8 6

D e trita l lo a d in rive rs8 7 8 6Sr/ Sr= 0 .7 1 7 8

D isslo ve d lo a d in rive rs Sr/ Sr= 0 .7 1 1 98 7 8 6

se d im e n t8 7 8 6Sr/ Sr= 0 .7 2 4

o c e a n8 7 8 6Sr/ Sr= 0 .7 0 8

Dissolved load in river 0.7119Detrital load in river 0.7178Sediment 0.724Seawater 0.708Hydrothermal vent 0.7035Oceanic crust 0.702

Geochemical Behaviors of Sr in the “Water World”

1. River water: (a) Reflect the Rb/Sr ratio and “age” of the source rocks;

(b) Sources derived from silicate and carbonate weathering

2. Seawater: (a) Chemically and isotopically “uniform” because of its

long residence time (~2 Ma); (b) Small but considerable regional difference in flux

and ICs occurred on time-scales shorter than the residence time;

(c) Non-conservative mixing in estuaries due to dynamic exchanges

Total mass of Sr in seawater= 1.25×1017 mol

After Basu et al., 2001

Oceanic Sr Budget

1, Steady or not? 2, How Sr ICs change with time?

(Assuming an average seawater concentration of 91.3 M)

Sampling Sites

Reference sites- ST-1 (NEC) and St-C (SCS)

119 120 121 122 123

Longitude (E)

119 120 121 122 123

22

23

24

25

26

Lat

titu

de

(N)

22

23

24

25

26

TAIW AN

S ou th C h in a S ea

KPC

SOT

715-2

South China Sea

Sample Locality

119.5 120.0 120.5 121.0

Longitude (E)

119.5 120.0 120.5 121.0

21.5

22.0

22.5

23.0

Latt

itu

de (

N)

21.5

22.0

22.5

23.0

TAIW AN

South China Sea

121.0 121.5 122.0 122.5 123.0

Longitude (E)

121.0 121.5 122.0 122.5 123.0

24.0

24.5

25.0

25.5

26.0

Lat

itu

de

(N)

24.0

24.5

25.0

25.5

26.0

TAIW AN

1

2

34 5 6

7

April

Aug.

Modern HydrographyTyphoon Toraji

Liang et al., 2003

WRA., 2003

Salinity (psu)

31 32 33 34 35

Tem

pera

ture

(o C

)

0

5

10

15

20

25

30

35

KuroshioSCSSummerWinter

RW

Wang et al., 2002

200-300 m

Kuroshio

NPTW

SCS

100 m

NPIW

PDW

400-600 m

>1300 m

Kao-Ping Canyon Sea Water Masses

RW0

100

Water mass Depth

SCSNPTW

200

SCS400

SCSNPIW

600

NPDW

1300

bottom

High-Precision Sr Isotopic Measurement P- TIMS

0.00E+00

5.00E+07

1.00E+08

1.50E+08

2.00E+08

2.50E+08

3.00E+08

3.50E+08

4.00E+08

4.50E+08

0.0 5.0 10.0 15.0 20.0 25.0

Column-1

Column-2

Column-3

Eluted volume (mL)

Inte

nsi

ty(c

ps)

Sr- Elution Curve

3N HNO3 8N HNO3 3N HNO3 0.05N HNO3

Seawater

ORI 679_S6-10 m

1. 0.709196±032. 0.709197±02

ORI 679_S3-10 m

1. 0.709195±032. 0.709195±02

SB_09-12 (10.5 m)

1. 0.709195±032. 0.709193±02

Recovery> 99.5%

TRITON TI

119.5 120.0 120.5 121.0

Longitude (E)

119.5 120.0 120.5 121.0

21.5

22.0

22.5

23.0L

atti

tud

e (

N)

21.5

22.0

22.5

23.0

TAIW AN

12

16

20

24

28

32

36

40

44

48

52

56

60

64

South China Sea

Δ87Sr (ppm)

The surface distributions of Sr ICs in the KPE

After Typhoon Toraji

1 2 0 1 2 1

2 2

2 3

Aug. 2001

S

31 .5

32 .5

33 .1

33 .3

33 .5

33 .7

33 .9

34 .1

34 .3

34 .5

Other Hydrographic Evidences

(Lin et al., 2003)

1 2 0 1 2 1

2 2

2 3

Aug. 2001

O -18

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

120 121

22

23

Aug. 2002

O -1 8

120 121

22

23

Aug. 2002

S

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

31.00 31.50 32.00 32.50 33.00 33.50 34.00

Δ87Sr= -39.11*S+1338.7r2=0.80

Δ87Sr= -10.82*S+377.08r2=0.70

EM-1

EM-2

EM-3

9.3 ppm(33.99‰)

Salinity (psu)

Δ87

Sr

(pp

m)

Freshening

Surface Seawater Sr ICs vs. Salinity

EM-1: Most radiogenic Sr IC--- (1) intense water-sediment interaction caused by flood plume (2) release radiogenic Sr from silicates due to stronger erosion

EM-2: Normal discharge of the Kao-ping river after heavy rainfalls

2σ

119 120 121 122 123

22

24

26

0.7060

0.7070

0.7080

0.7090

0.7110

0.7120

0.7130

0.7140

0.7150

0.7160

0.7170

121.0 121.5 122.0 122.5 123.0

Longitude (E)

121.0 121.5 122.0 122.5 123.0

24.0

24.5

25.0

25.5

26.0

Lat

itu

de

(N)

24.0

24.5

25.0

25.5

26.0

TAIW AN

Okinawa Trough

20

24

28

32

36

40

44

48

1

2

34 5 6

7

Sr Isotopic Characteristics of the Taiwan River

Δ87Sr (ppm)

Mixing processes of the Water masses--- Evidence from the vertical profiles of the Sr ICs at the SOT

0

100

200

300

400

500

600

700

800

900

1000

1100

0.70915 0.70918 0.70920 0.70923 0.70925

87Sr/86Sr

Dep

th (

m)

ST-1

NEC

0

100

200

300

400

500

600

700

800

900

1000

1100

0.70915 0.70918 0.70920 0.70923 0.70925

87Sr/86Sr

Dep

th (

m)

St-C

SCS

0

100

200

300

400

500

600

700

800

900

1000

1100

0.70915 0.70918 0.70920 0.70923 0.70925

87Sr/86Sr

Dep

th (m

)

NPTW

NPIW

SW

SOT

S1

S6

S3

0.709176 0.709182 0.709176

Seawater Sr ICs is “not” isotopic uniform in the open ocean and marginal sea,but it seems to have a similar pattern in the same region.

0

2

4

6

8

10

0 50 100 150 200 250 300 350 400 450Na (mM)

Ca

(mM

)

st 1-Ca

st 2-Ca

st 3-Ca

st 4-Ca

st 5-Ca0

10

20

30

40

50

60

0 50 100 150 200 250 300 350 400 450Na (mM)

Mg

(m

M)

st 1-Mg

st 2-Mg

st 3-Mg

st 4-Mg

st 5-Mg

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250 300 350 400 450Na (mM)

Sr

(μM

)

0

2

4

6

8

10

12

U (n

M)

st 1-Srst 2-Srst 3-Srst 4-Srst 5-Srst 1-Ust 2-Ust 3-Ust 4-Ust 5-U

0

100

200

300

400

500

600

0 50 100 150 200 250 300 350 400 450Na (mM)

B (

μM

)

0

1

2

3

4

5

6

Ba (μ

M)

st 1-Bst 2-Bst 3-Bst 4-Bst 5-Bst 1-Bast 2-Bast 3-Bast 4-Bast 5-Ba

0.7085

0.7090

0.7095

0.7100

0.7105

0.7110

0.7115

0.7120

0.7125

0.7130

0.7135

0.00 0.05 0.10 0.15 0.20 0.25 0.30

1/Sr (μM-1)

87S

r/86

Sr

Surface

Bottom

0.7085

0.7090

0.7095

0.7100

0.7105

0.7110

0.7115

0.7120

0.7125

0.7130

0.7135

0 100 200 300 400 500

Cl (mM)

87S

r/86

Sr

Surface

Bottom

(a) (b)

(c)

Summary

• High precision Sr isotopic measurement can be applied as a new sensitive tracer for studying water mass mixing near estuary

• Rather large variation in 87Sr, >60 ppm, was detected in the Kao-ping estuary and possibly were affected by flood plume, river discharge and surface seawater mass

• Vertical seawater Sr ICs is “not” isotopic uniform in the open ocean and marginal sea

• Dynamic exchange among freshwater, groundwater and seawater are occurring in the Kaoping River estuary and canyon

Summary (continue)

• High dissolved B and Sr in the Kaoping River emphasize the potential impact of mountainous island to the global oceanic chemical budget

• The dissolved REE patterns of the Kaoping River at different tributaries show similar negative Ce anomaly and HREE enrichment

• Strong positive Gd anomaly supports an anthropogenic p

ollution in the river.

• The Sr isotopic variations are rather large, 0.712649~ 0.713592, and show systematically decreasing ratios with distance from the coastal region

THANKS FOR YOUR ATTENTIONEDSRC-NCKU, Taiwan