ACTA SEDIMENTOLOGICA SINICA Vol. 28 No. 6 Dec m NaCl CaSO 4 2H 2

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1 ACTA SEDIMENTOLOGICA SINICA Vol. 28 No. 6 Dec m NaCl CaSO 4 2H 2 O Na 2 SO 4 10H 2 O Na 2 SO 4 Na 2 Ca SO 4 2 K 2 MgCa 2 SO 4 4 2H 2 O Na 4 Ca SO 4 3 2H 2 O Na 2 Mg SO 4 2 4H 2 O BaSO 4 Ca 2 Na 2 CO 3 3 Ca 2 Na 3 SO 4 3 OH NaHCO 3 Na 2 Ca CO 3 2 5H 2 O Na 2 CO 3 H 2 O CaMg B 3 O 3 OH 5 2 6H 2 O Na-SO4 Na-Cl Na-Ca-SO 4 Na-SO 4 Na-SO 4 - Cl Na-Ca-SO 4 -Cl Ca-SO 4 Na-Mg-SO 4 1 Ma ~ Ma ~ Ma ~ Ma 0. 5 ~ lmh804@ gmail. com X141 P A '35. 3 N 92 30'32. 7 E m 1 80 km mm /yr mm /yr 3. 7 ~ 4. 2 m /s 13 1 ~ ~ cm 400 m kzcx2-yw

2 Fig. 1 1 Chen Brown Map of the Qaidam basin showing sampling sites cited from Chen and Brown X X 2. 1 a Rigaku D /MAX 2000 Cu Ka kv 40 ma 3 ~ 65 step /min 352 NaCl CaSO 4 2H 2 O CaSO 4 Na 2 SO 4 10H 2 D /max 12kW Cu Kα O Na 2 SO 4 Na 2 Ca SO nm 40 kv 100 ma 8 /min step θ X 3 ICP MS X ~ 10 mg Teflon 77 1 ml 1 ml Teflon 20 min 150 Na 4 Ca SO 4 3 2H 2 O Na 2 Mg SO 4 2 4H 2 O K 2 MgCa 2 SO 4 4 2H 2 O 1 ml 1 ml Teflon Ca 2 Na 2 CO 3 3 Ca 2 Na 3 SO min 190 OH NaHCO 3 Na 2 Ca 24 h Teflon 150 CO 3 2 5H 2 O Na 2 CO 3 H 2 O 1 ml MgCO 3 BaSO 4 2 ml 20 min 3 ml CaMg B 3 O 3 OH 5 2 6H 2 O h 100 ml SO 2-4 Cl ~ 385 m mm cm 4a b 6 X 3

6 1215 Fig. 2 2 400 m Evaporative mineral versus depth in the upper 400 m of the core 8. 95 ~ 9. 0 m 139 ~ 139. 35 m 139. 8 ~ 140. 35 m 205 ~ 205. 25 m 209 ~ 209. 25 m 280. 3 38. 6 ~ 39.

3 Fig m Evaporative mineral versus depth in the upper 400 m of the core ~ 9. 0 m 139 ~ m ~ m 205 ~ m 209 ~ m ~ m 40 ~ m ~ m ~ m 4e f ~ m 4c d 121 ~ m ~ 140 m ~ m ~ m ~ m ~ m ~ m

4 X A 8. 3 ~ m B ~ m C ~ 121 m D 121 ~ m E ~ m Fig. 3 X-ray diffraction of evaporative minerals. Samples are from the depths of A 8. 3 ~ m B ~ m C ~ 121 m D 121 ~ m and E ~ m 9. 3 ~ m 2 4g 2 4h 108 ~ m 10 ~ m 41 ~ m 59 ~ m ~ 121 m ~ m ~ m > 45 cm > 300 cm 400 m ~ 9. 0 m ~ m ~ m ~ ~ m ~ m ~ m m ~ m ~ m ~ m ~ cm m ~ 144 m ~ m 2 1 4c ~ m ~ m 5

6 1217 4 a 242. 6m b 135. 25m c Eu 8. 95m d 36. 9m e 160. 4m f 121m g 9. 7m h 120. 8m Fig. 4 Microphotograph and photos of hand specimen of evaporative minerals a Blocky halite hand specimen at 242.

5 a m b m c Eu 8. 95m d 36. 9m e m f 121m g 9. 7m h m Fig. 4 Microphotograph and photos of hand specimen of evaporative minerals a Blocky halite hand specimen at m b Microphotograph of cubic halite at m c SEM of lenticular thenardite with needle-shaped eugsterite at 8. 95m d Blocky thenardite at 36. 9m e auberite hand specimen at m f Microphotograph of glauberite at 121m g Polyhalite hand specimen at 9. 7m h Grain bloedite in m

6 Table m Lithology and minerals in the upper 400m sediments in the core / 2. 7 ~ 8m 1 5cm 3. 9 ~ 3. 95m < 20mm 1 ~ 3mm Cal Pl Ch Am Ca Ar 8 ~ m 1st ~ m ~ m 2nd ~ m ~ 30m 3rd 8 15 ~ 105cm 8 ~ 9. 05m < 9. 3 ~ m ~ m 11 ~ 10mm < 10mm Ph Eu m ~ m 13 ~ m 9. 3 ~ m 11 ~ ~ m ~ m m Ce ~ 115cm ~ m ~ m ~ m - - < 20mm < 10mm < 10mm < 2mm ~ 18. 6m < 20mm 6 5 ~ 175cm ~ 28. 6m < ~ 28. 9m 29 ~ 29. 1m ~ 10mm < 10mm 29. 4m ~ 29. 8m ~ 30m Ma Ta Cr Am Ca Ar - - Ma Am Pl M Ch Ka Am Ca 30 ~ 36. 3m ~ m 4th ~ m ~ 35. 9m 2 5cm ~ m < 30mm ~ m 1 ~ 5mm 12 5 ~ 175cm ~ m ~ m ~ Eu m ~ m 40 ~ m < 10mm ~ m ~ m ~ < 10mm Ce m ~ 42. 3m 43 ~ m Ga ~ m ~ m Mi < 10mm Cal Pl M Ch Ka Am Ca Ar Am Ta Ma Ca Am Ca Ar ~ m 5th ~ 77. 6m ~ m 6th Eu 3 35 ~ 125cm 57 ~ m < 5mm < Ce ~ m ~ m 6mm Ga Ta ~ 83. 5m ~ m Cal < 9mm Am Ca T Ar 10 5 ~ 275cm ~ m ~ m ~ m < ~ m ~ m ~ 8mm < Eu m ~ m ~ 10mm Cal m 87 ~ m ~ m Am Ca Ar Ma

7 ~ m ~ m 7th ~ m ~ 75cm ~ m ~ m ~ m ~ m ~ m ~ m 1 < 3mm Am Ca Ar < 10mm ~ m < 10mm ~ m < 8mm ~ m Cal Eu M Am Ch Ka M Am Ma ~ m 8th ~ m ~ m 9th 2 55 ~ 115cm ~ m 107 ~ m 2 90 ~ 385cm ~ m ~ m ~ m 1 5 ~ cm ~ m ~ m 10th ~ 182m 182 ~ m 11th ~ m ~ m 12th ~ m ~ 385cm ~ m 131 ~ m ~ m ~ m ~ m 139 ~ m ~ m ~ m ~ m ~ m ~ m ~ m ~ m 2 5 ~ 15cm ~ m ~ m 2 15 ~ 45cm 182 ~ m ~ m 10 5 ~ 95cm ~ m ~ m ~ m ~ m ~ m ~ m 205 ~ m ~ m ~ ~ m < 5mm < 10mm Bl < 3mm ~ m Ga < 8mm ~ m ~ m ~ Eu m ~ m Bl ~ m < 30mm < 9mm ~ m Eu < 10mm < 6mm < 20mm 1 ~ 5mm < 5mm < 15mm ~ m < 8mm ~ m ~ m < 8mm 205 ~ m ~ m 5% ~ 10% - < 10mm Cal In Ga Cal Eu Ga Ka Am M Ca Ar Ma Ka Am M Ca Ar Ma Ma Q Pl Ch Am M Ca Ar Ma Ma M Ca Ar M Am M Am

8 ~ m 13th 9 5 ~ 115cm ~ m ~ m ~ m ~ m ~ m ~ m ~ m ~ m ~ m < 40mm < 8mm Ba 1 M Am ~ m 2 5 ~ 25cm ~ m ~ m < 30mm ~ m ~ m < 5mm Ma ~ m 14th 2 45cm ~ m ~ 260m - - < 6mm ~ m 20 ~ 30mm ~ m Ma 260 ~ m 15th 3 5 ~ 55cm 260 ~ m < 15mm ~ m ~ m < 5mm ~ m - - < 6mm m ~ m In Na ~ m 16th 2 5 ~ 85cm ~ m ~ m ~ m ~ m ~ m < 15mm ~ m < 8mm Ank ~ m 12 5 ~ 25cm 291 ~ m ~ m ~ m ~ m ~ m ~ m ~ m ~ m ~ m ~ m ~ m ~ m ~ 288m ~ m 298 ~ m 295 ~ m ~ m ~ m ~ m 345 ~ m ~ m ~ m 331 Cal ~ m 315 ~ m ~ Ba m ~ m ~ m ~ m 343 ~ m < 6mm Ana Ank ~ m 17th 2 45cm ~ m < 5mm ~ m 1 5cm ~ m 376m 376 ~ m 30mm ~ m ~ m ~ m ~ m 382 ~ 382. Ba 05m 1 ~ 5mm Ana Ca Ar ~ m 18th 4 5 ~ 75cm ~ m ~ m ~ m ~ m < 20mm < 12mm Ana Ca Ar Ma- Q- Or- Al- Pl- Ka- Ca- Ar- - M- Ch- Sm- Cr- Ta- - Cal Mi- Ba- Ce- Am- Ga- T- In- Na- Ank- -Ana

6 1221 5 a 3. 2 m b 19. 4 m c 25. 7 m d 4. 8 m e 135. 8 m f 261. 1 m g 163. 8 m h 136. 15 m i 39. 8 m j 16. 9 m k 4. 1 m l 385. 9 m Fig. 5 Photos of various gypsum crystals a Slender gypsum at 3.

9 a 3. 2 m b m c m d 4. 8 m e m f m g m h m i m j m k 4. 1 m l m Fig. 5 Photos of various gypsum crystals a Slender gypsum at 3. 2m b Prismatic gypsum at 19. 4m c Stubby gypsum at 25. 7m d Tabular - stubby gypsum at 4. 8m e Tabular gypsum at m f Pyramid gypsum at m g Pedogenic gypsum at m h Microscopy of pyramid gypsum at m i Aggregation of pyramid gypsum at 39. 8m j Radial gypsum aggregation at 16. 9m k psum twines at 4. 1m l psum intersecting glauberite at m m SO 2 4 Ca Mg Na Ca Mg K K Cl Na B 6 Na 30% ~ 40% 3 Na ~ m ~ m ~ m ~ m ~ m ~ m 205 ~ m ~ m ~ m ~ m Ca K Mg B Br /Cl Na 6 B 200 μg /g Ca Mg Na SO 2-4 B Na- 15% 8% K 2% SO 2 4 Cl Mg-Ca -Cl 0. 09% ~ % 0. 46% ~ % Eugster rdie ~ m ~ m ~ m ~ m ~ m ~

10 Fig Ph- - Bl- - Relationship between the changes of actions and anions and brine types salt minerals and evaporative stages -psum -lite Ph-Polyhalite -enardite Bl-Bloedite -auderite 25% Mg X Mg 7 Na Na-Ca Na- Mg Ca 108 ~ m ~ m Na-Cl

11 Eugster and rdie Na 2. Na- Ca 3. Na- Ca - Mg 4. Na- Mg 5. Na-Ca 6. Na-Ca- Mg 7. Na-Mg- Ca 8. Na-Mg 9. Na-Ca-Mg 10. Ca- Na 11. Ca- Mg - Na 12. Ca-Mg- Na 13. Mg- Ca - Na 14. Mg- Na 15. Ca 16. Ca- Mg 17. Ca-Mg 18. Mg- Ca 19. Mg 5% ~ 25% Fig. 7 Major cations distribution on the brine classification after Eugster and rdie Na 2. Na- Ca 3. Na- Ca - Mg 4. Na- Mg 5. Na-Ca 6. Na-Ca- Mg 7. Na-Mg- Ca 8. Na-Mg 9. Na-Ca-Mg 10. Ca- Na 11. Ca- Mg - Na 12. Ca-Mg- Na 13. Mg- Ca - Na 14. Mg- Na 15. Ca 16. Ca- Mg 17. Ca-Mg 18. Mg- Ca 19. Mg. Ions shown in parentheses ranging from 5% to 25%. K Θ > J ΔG > 0 ΔG > 0 K Θ = J K Θ < J ΔG < ~ SO 2-4 ΔG < 0 Na-Ca-SO 4 Na-SO 4 Na-SO 4 -Cl Na-Ca-SO 4 -Cl Ca-SO 4 Na-Mg-SO Gibbs 21 Ca SO H 2 O CaSO 4 2H 2 O 1 2Na + + SO 2-4 Na 2 SO 4 2 Gibbs ΔG < 0 ΔG = RTlnK Θ + RTlnJ = RTln K Θ /J K Θ Christov Moller C 1 atm 23 Fig. 8 Ca-brine evolution on 45 and 60 R R = T From Christov and Moller 2004 J = 1 / Ca 2 + SO 2-4 = 1 / Na + 2 SO 2-4 J

12 CaSO 4 -Na 2 SO 4 -H 2 O Ca Vergouwen 31 Mg 2 + K + SO 2-4 Cl - 6 SO 2-4 Ca Cl - SO 2-4 Ca 2 + Mg 2 + K Na + Ca 2 + SO 2 4 Na / Ca > ~ 9. 0 m ~ m ~ Na 2 SO 4 10H m 2 O ~ 40. 4m Na 2 SO ~ 88. 7m 4 Na-SO ~ CaSO 4 2H 2 O + 4Na + + 2SO 2 4 Na 4 Ca SO 4 3 2H 2 O 2Na 2 SO 4 + Ca + SO 2 4 Na 2 SO 4 CaSO 4 2H Eugster rdie 20 2 O Mees 27 Ortí 28 Na + 2CaSO 4 2H 2 O + 2Na + CaSO 4 Na 2 SO 4 + Ca H 2 O 2Na 2 SO 4 CaSO 4 2H 2 O Na 2 SO 4 Na Ca CaSO 4 + Na 2 SO 4 + 2H 2 O g Gibbs 30g 36. 4g 2Na 2 SO 4 + Mg H 2 O Na 2 Mg SO 4 2 4H 2 O + 2Na + Freyer 30 Na 2 SO 4 -CaSO 4 -H 2 O 2Na 2 SO 4 CaSO 4 + 2H 2 O g 2Na 2 SO 4 CaSO 4 2H 2 O 5a b 110 H ~ 121 m X OH % ~ m 108 ~ m ~ 5c m 2 Mg 38 Magee 33 Mg 5d e 5g

13 Na + 5f h Ma 340 m 1 Ma 5i j k 410 m 4. 1 m m m ZK l ph ZK m ph 0. 75Ma 340 m Ma 9 Gibbs m ZK m Ma Fig. 9 9 ZK Comparison between the core in this study and ZK402 core in Dalangtan from Philipps et al. 1993

14 Ca-SO 4 -Cl Ca-SO 4 Na-Mg-SO ~ Ma ~ m Ma ~ m Ma 400 m ~ m 0. 7 Ma m ⑴8 ~ m ⑵ ~ ~ m ⑶ ~ m ⑷36. 3 ~ m ⑸ Ma 57 ~ m ⑹77. 6 ~ m ⑺ ~ m ⑻ ~ m ⑼ ~ m ⑽ ~ m ⑾ m ⑿ m ⒀ ~ m ⒁ ~ m ⒂260 ~ m ⒃ ~ m ⒄ ~ m Ma ⒅ ~ m ~ Ma ~ Ma References 1 Wang Q Coward M P. e Qaidam Basin NW China formation m 1 NaCl CaSO 4 2H 2 O Na 2 SO 4 10H 2 O Na 2 SO 4 Na 2 Ca SO 4 2 K 2 MgCa 2 SO 4 4 2H 2 O Na 4 Ca SO 4 3 2H 2 O Na 2 Mg SO 4 2 4H 2 O 2 Salt Lake J Ca 2 Na 2 CO 3 3 Ca 2 Na 3 SO 4 3 OH NaHCO 3 Na 2 Ca CO 3 2 5H 2 O Na 2 CO 3 H 2 O CaMg B 3 O 3 OH 5 2 6H 2 O BaSO 4 3 / / 4 8 Na-SO 4 J 5 Na Ca Mg Cl SO 2-4 Na-Cl Na-Ca-SO 4 Na-SO 4 Na-SO 4 -Cl Na ~ Ma 18 and hydrocarbon potential J. Journal of Petroleum Geology Song T Wang X. Structural styles and stratigraphic patterns of syndepositional faults in a contractional setting examples from Qaidam basin northwestern China J. AAPG Bulletin Wang E. Displacement and timing along the northern strand of the Altyn Tagh fault zone Northern Tibet J. Earth Planetary Science Letter J. D Liu Xingqi Cai Keqin Yu Shengsong. Geochemical simulation of the formation of brine and salt minerals based on Pitzer model in Caka. Science in China Series D Wang F Lo C Li Q et al. Onset timing of significant unroofing a- round Qaidam Basin northern Tibet China constraints from 40 Ar / 39 Ar and FT thermochronology on granitoids J. Journal of Asian Earth Sciences Zhu Y Weng H Su A et al. Geochemical characteristics of Tertiary saline lacustrine oils in the Western Qaidam Basin northwest China J. Applied Geochemistry Owen L A Finkel R C Ma H et al. Late Quaternary landscape evolution in the Kunlun Mountains and Qaidam Basin Northern Tibet A framework for examining the links between glaciation lake level changes and alluvial fan formation J. Quaternary International Wang Chunnan Guo Xinhua Ma Mingzhu et al. Ore-forming geological background of K-Mg salt in Qarhan Salt Lake J. Northwestern Geology Rieser A B Bojar A V. Neubauer F et al. Monitoring Cenozoic climate evolution of northeastern Tibet stable isotope constraints from the

15 western Qaidam Basin China J. International Journal of Earth Sciences Geol Rundsch 2008 DOI /s Wang A Smith J A Wang G et al. Late Quaternary river terrace sequences in the eastern Kunlun Range northern Tibet A combined record of climatic change and surface uplift J. Journal of Asian Earth Sciences Crowley J K. Mapping playa evaporite minerals aviris data A first report from Death Valley California J. Remote Sensing of Environment Bryant R G Sellwood B W Millington A C et al. Marine-like potash evaporite formation on a continental playa case study from Chott el Djerid southern Tunisia J. Sedimentary Geology J J Zhang Youxun Xuan Zhiqiang. Economic evaluation of potassium and magnesium solid deposit in Kunteyi and Mahai Salt Lake of Qinghai Province J. Journal of Salt Lake Science Taoudenni-Agorgott basin northern Mali J. Sedimentary Geology J Xuan Zhiqiang. Basic characteristic of potassium and magnesium solid deposit in Kunteyi and Mahai salt lake of Qinghai province J. Journal of Salt Lake Sciences Chen K Bowler J M. Late Pleistocene evolution of salt lakes in the Qaidam Basin Qinghai province China J. Palaeogeography Palaeoclimatology Palaeoecology Freyer D Fischer St K hnke K et al. Formation of double salt hydrates 16 Lowenstein T K Spencer R J Zhang P. Origin of ancient potash evaporites Clues from the modern nonmarine Qaidam Basin of Western I. Hydration of quenched Na 2 SO 4 CaSO 4 phases J. Solid State Ionics China J. Science Vergouwen L. Eugsterite a new salt mineral J. American Mineral- 17. ogist M Wei Xinjun Shao Changduo Wang Mili et al. Material Constituents Depositional Features and Formation Conditoins of Po Last W M. Continental brines and evaporites of the northern Great Plains of Canada J. Sedimentary Geology Mees F Stoops G. Mineralogical study of salt efflorescences on soils tassium-rich Salt Lakes in Western Qaidam Basin M. Beijing Geological House Vengosh A Chivas A R Starinsky A et al. Chemical and boron isotope compositions of non-marine brines from the Qaidam Basin Qinghai China J. Chemical Geology Liu W G Xiao Y K Peng Z C et al. Boron concentration and isotopic composition of halite from experiments and salt lakes in the Qaidam Basin J. Geochimica et Cosmochimica Acta Eugster H P rdie L A. Saline lakes M Lerman A ed. Lakes Accumulation M. Englewood Cliffs N. J. Prentice ll Christomir Christov Nancy Moller. A chemical equilibrium model of solution behavior and solubility in the H-Na-K-Ca-OH-Cl-HSO 4 -SO 4 - H 2 O system to high concentration and temperature J. Geochimica et Cosmochimica Acta M Liu Qun Chen Yuhua Li Yincai et al. Mesozoic and Cenozoic Terrigenous Clastic China Chemical-type Salt Deposition M. Beijing Beijing Science and Technology Publishing House M Qu Yihua Qian Ziqiang n Weitian. ndbook of Salt Minerals M. Beijing Geological Publishing House Hu Xiaojin. Study of exploitation on the brine of Luobupo Salt Lake J. Geology of Chemical Minerals Mees F. e alteration of glauberite in lacustrine deposits of the Ort F G ndogan I Helvaci C. Sodium sulphate deposits of Neogeneage the Kirmir Formation Beypazari Basin Turkey J. Sedimentary Geology Conley R F Bundy W M. Mechanism of gypsification J. Geochimica et Cosmochimica Acta of the Jequetepeque Valley northern Peru J. Geoderma Okada A Yabuki S Liu C Q et al. Distribution of salt-constituting chemical species in the desert soils of the Turpan Basin and Junggar Basin Xinjiang China J. Journal of Arid Land Studies Mees F Singer A. Surface crusts on soils /sediments of the southern Aral Sea basin Uzbekistan J. Geoderma Edinger S E. An investigation of the factors which affect the size and growth rates of the habit faces of gypsum J. Journal of Crystal Chemistry Geology Physics. Springer-Verlag Growth M Staff Room of Inorganic Chemistry Dalian University of Technology. Inorganic Chemistry M. Beijing Higher Cody R D Shanks H R. A comparison of calcium sulphate dihydrate grown in clay gels and in sodium silicate gels J. Journal of Crystal Growth Education Press Cody R D. Lenticular gypsum occurrences in nature and experimental 22 Warren J K. Evaporite Sedimentology Importance in Hydrocarbon determinations of effects of soluble green plant material on its formation J. Journal of Sedimentary Petrology Cody R D Cody A M. psum nucleation and crystal morphology in

16 analog saline terrestrial environments J. Journal of Sedimentary Petrology Philipps F M Zreda M G Ku T L et al. 230 /U 234 and Cl 36 dating of evaporate deposits from the western Qaidam Basin China-implications for glacial period dust export from Central Asia J. Geological Society of America Bulletin Evaporative Minerals of the Upper 400m Sediments in a Core from the Western Qaidam Basin Tibet LI Ming-hui 1 YI Chao-lu 2 FANG Xiao-min 1 GAO Shao-peng 2 ZHANG Wei-lin 1 1. Institute of Tibetan Plateau Research Chinese Academy of Sciences ITPCAS Beijing e Laboratory of Continental Collision and Plateau Uplift ITPCAS Beijing Abstract Qaidam Basin is a tectonically controlled depression on the northern margin of the Tibetan Plateau. In 2008 a long core was drilled in Qahansilatu sub-basin in the western Qaidam Basin. e sediment layers in the upper 400 m alternate between evaporative mineral layers and carbonaceous clay layers. e detailed mineralogical investigation focused on evaporative minerals including halite gypsum mirabilite thenardite glauberite eugsterite bloedite barite cesanite shortite thermonatrite gaylussite nahcolite and inderborite. psum and halite make up the majority of the evaporative minerals. Environmentally induced variations in the mineralogy and crystal habit of the sulfates have been extensively investigated. psum has prismatic and pyramid habits such as disc pyramid stubby prismatic slender prismatic. Visible isolated gypsum and aggregates rosette /radial and twins are mostly scattered in carbonaceous clay layers suggesting secondary gypsum well developed. psum may be a precursor mineral of glauberite and thenardite is the precursor of bloedite. As a metastable and rare mineral eugsterite does not appear in other Tibetan areas. It forms at the expense of pre existing gypsum or thenardite in the core at an experimental temperature of higher than room temperature. e presence of eugsterite indicates a warm and / or hot climate at its deposition time. Mineralogical variations have been explained by the brine evolution of Na-Cl Na-Ca-SO 4 Na-SO 4 Na-SO 4 - Cl Na-Ca-SO 4 -Cl Ca-SO 4 and Na-Mg-SO 4. For instance Na-Mg-SO 4 type corresponds to the bloedite while Na- Ca-SO 4 -Cl type to the assemblage of halite gypsum and glauberite. e evaporative minerals and carbonaceous clay layers alternation indicates the shift between dry and wet climate. According to the thickness eighteen evaporative stages and /or dry climate stages were identified from Ma to about Ma. e two early dry climate stages are identified at ~ Ma and Ma. e other sixteen evaporative stages occurred from Ma to about Ma. e evaporate-rich stages suggested that evaporation was high and groundwater inflow was sufficient at the subbasin. Key words evaporative minerals geochemistry halite gypsum Qahansilatu sub-basin Qaidam Basin

km 5 km Pt 2 x 2 1 Au 65 ~ ~ km 5 km 10 km 2 Au Au

km 5 km Pt 2 x 2 1 Au 65 ~ ~ km 5 km 10 km 2 Au Au 38 1 2015 3 JOURNAL OF EAST CHINA INSTITUTE OF TECHNOLOGY Vol. 38 No. 1 Mar. 2015 doi 10. 3969 /j. issn. 1674-3504. 2015. 01. 002 1 2 1 2 3 1. 471000 2. 471000 3. 510640 9 P618. 51 A 1674-3504 2015 01-0012-11.