地球46億年的歷史中，雪球地球事件是影響地球發展的重要氣候事件之一。當時地球被冰雪所覆蓋，僅部分海底熱液系統仍存在液態水。如此極端的氣候條件，對岩石圈、水圈、大氣圈、生物圈之間的交互作用產生深遠影響。因此研究雪球地球事件前後的環境變化，有助於我們更深入理解地球的運作機制。本研究樣品來自南中國貴州甕安地區穿岩洞剖面的陡山沱層，該岩層橫跨約一億年，是研究長時間尺度古環境變化的理想材料。過去研究顯示，全岩分析可能會對古環境地球化學指標造成一定程度的干擾，因此本研究使用序列萃取法針對碳酸鹽相進行分析，以獲得更準確的環境訊號。樣品經XRD、偏光顯微鏡與SEM鑑定礦物組成，結果顯示主要由白雲石以及磷灰石組成。拉曼光譜儀分析中，殘餘碳的特徵峰隨石墨化程度而變化，推算樣品CYD-7.5以及CYD-14.5所歷經最高溫度分別為137℃、212℃。在序列萃取的過程中，Mg/Ca接近1且P/Ca接近0代表白雲岩相；Mg/Ca接近0且P/Ca接近600代表磷酸鹽相。根據此標準，CYD-7.5、CYD-9.5、CYD-14.5為白雲岩相，CYD-25為磷酸鹽相。Mn/Sr常作為成岩作用的指標，與樣品中87Sr/86Sr沒有明顯的共變，符合過去針對雪球地球事件曾處於高Mn海水狀況的結果。若碳酸鹽受後期成岩作用的影響，Sr/Ca會上升，本研究的Sr/Ca與87Sr/86Sr呈現良好的共變結果，顯示序列萃取前段屬於受後期成岩作用影響的碳酸鹽相。在87Sr/86Sr與Sr/Ca的圖中，當萃取步驟進行到S9-S11時，其87Sr/86Sr與Sr/Ca趨於穩定，且其他地球化學指標亦無顯著變化，推測此處所萃取為最接近原始訊號的碳酸鹽相。由於S10、S11所使用之萃取液為10 % (v/v) 的醋酸，可能會溶解其他較脆弱的礦物相，因此本研究將S9設為最接近原始碳酸鹽訊號的區間。穿岩洞剖面陡山沱層上段所測得的87Sr/86Sr介於0.708870 - 0.709163，δ88Sr則介於0.29 - 0.36 ‰ ，其變化都與過去楊子地塊的其他研究地點所得到的結果十分接近，顯示同一地區的資料具有良好一致性。然而，本研究中其他樣品的Sr同位素分析尚未完成，未來仍須補足，以進行更深入的古環境變化分析。

The Snowball Earth event was a global glaciation that occurred during the Neoproterozoic period. This extreme climate change had a profound impact on Earth’s evolution. The Doushantuo Formation at Chuanyangdong (CYD) experienced two glaciation events, making it an excellent archive for studying long-term paleoenvironmental and climate change. However, the whole rock geochemical analysis may obscure the original seawater signals due to mixed mineral phases. Therefore, it is necessary to apply sequential extraction methods to isolate the primary carbonate phase.
In this study, mineral compositions were identified using XRD, polarized light microscopy, SEM. Maximum temperatures were estimated based on Raman spectroscopy, where the characteristics of carbon peaks vary with the degree of graphitization.
In samples CYD-7.5, CYD-9.5, and CYD-14.5, Mg/Ca ratios close to 1 and the P/Ca ratios near zero indicate successful isolation of the dolomite phase. Although the Mn/Sr ratio is commonly used to assess late-stage diagenesis, the lack of correlation between Mn/Sr and 87Sr/86Sr suggests that the post-glacial seawater was anoxic and enriching in Mn.
The correlation between Sr/Ca and 87Sr/86Sr ratios in earlier extraction steps indicates possible alteration in those phases. In contrast, step S9 show minimum variation in 87Sr/86Sr, Sr/Ca, and other geochemical proxies, suggesting that it best represent the original seawater signal.
The variation in 87Sr/86Sr and δ88Sr from CYD are consistent with previous studies from other parts of the Yangtze Platform. Further analysis od additional samples from the CYD section is required to fully characterize Sr isotope variations across the Doushantuo Formation.

Bailey, T. R., McArthur, J. M., Prince, H., & Thirlwall, M. F.. Dissolution methods for strontium isotope stratigraphy: whole rock analysis. Chemical Geology, 167(3-4), 313-319. (2000).

Banner, J. L., & Hanson, G. N.. Calculation of simultaneous isotopic and trace element variations during water-rock interaction with applications to carbonate diagenesis. Geochimica et Cosmochimica Acta, 54(11), 3123-3137. (1990).

Beyssac, O., Goffé, B., Chopin, C., & Rouzaud, J. N.. Raman spectra of carbonaceous material in metasediments: a new geothermometer. Journal of metamorphic Geology, 20(9), 859-871. (2002).

Beyssac, O., Goffé, B., Petitet, J. P., Froigneux, E., Moreau, M., & Rouzaud, J. N.. On the characterization of disordered and heterogeneous carbonaceous materials by Raman spectroscopy. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 59(10), 2267-2276. (2003).

Boger, S. D., & Miller, J. M.. Terminal suturing of Gondwana and the onset of the Ross–Delamerian Orogeny: the cause and effect of an Early Cambrian reconfiguration of plate motions. Earth and Planetary Science Letters, 219(1-2), 35-48. (2004).

Brasier, M. D., Shields, G., Kuleshov, V. N., & Zhegallo, E. A.. Integrated chemo-and biostratigraphic calibration of early animal evolution: Neoproterozoic–early Cambrian of southwest Mongolia. Geological Magazine, 133(4), 445-485. (1996).

Chao, H. C., You, C. F., Liu, H. C., & Chung, C. H.. Evidence for stable Sr isotope fractionation by silicate weathering in a small sedimentary watershed in southwestern Taiwan. Geochimica et Cosmochimica Acta, 165, 324-341. (2015).

Condon, D., Zhu, M., Bowring, S., Wang, W., Yang, A., & Jin, Y.. U-Pb ages from the neoproterozoic Doushantuo Formation, China. science, 308(5718), 95-98. (2005).

Fietzke, J., & Eisenhauer, A.. Determination of temperature‐dependent stable strontium isotope (88Sr/86Sr) fractionation via bracketing standard MC‐ICP‐MS. Geochemistry, Geophysics, Geosystems, 7(8). (2006).

Halicz, L., Segal, I., Fruchter, N., Stein, M., & Lazar, B.. Strontium stable isotopes fractionate in the soil environments?. Earth and Planetary Science Letters, 272(1-2), 406-411. (2008).

Halverson, G. P., Dudás, F. Ö., Maloof, A. C., & Bowring, S. A.. Evolution of the 87Sr/86Sr composition of Neoproterozoic seawater. Palaeogeography, Palaeoclimatology, Palaeoecology, 256(3-4), 103-129. (2007).

Halverson, G. P., Hoffman, P. F., Schrag, D. P., Maloof, A. C., & Rice, A. H. N.. Toward a Neoproterozoic composite carbon-isotope record. Geological Society of America Bulletin, 117(9-10), 1181-1207. (2005).

Hoffman, P. F., Abbot, D. S., Ashkenazy, Y., Benn, D. I., Brocks, J. J., Cohen, P. A., ... & Warren, S. G.. Snowball Earth climate dynamics and Cryogenian geology-geobiology. Science Advances, 3(11), e1600983. (2017).

Hoffman, P. F., Kaufman, A. J., Halverson, G. P., & Schrag, D. P.. A Neoproterozoic snowball earth. science, 281(5381), 1342-1346. (1998).

Hoffman, P. F., & Schrag, D. P.. The snowball Earth hypothesis: testing the limits of global change. Terra nova, 14(3), 129-155. (2002).

Jacobsen, S. B., & Kaufman, A. J.. The Sr, C and O isotopic evolution of Neoproterozoic seawater. Chemical Geology, 161(1-3), 37-57. (1999).

James, N. P., Narbonne, G. M., & Kurtis Kyser, T.. Late Neoproterozoic cap carbonates: Mackenzie Mountains, northwestern Canada: precipitation and global glacial meltdown. Canadian Journal of Earth Sciences, 38(8), 1229-1262. (2001).

Jiang, G., Kaufman, A. J., Christie-Blick, N., Zhang, S., & Wu, H.. Carbon isotope variability across the Ediacaran Yangtze platform in South China: Implications for a large surface-to-deep ocean δ13C gradient. Earth and Planetary Science Letters, 261(1-2), 303-320. (2007).

Kaufman, A. J., Jacobsen, S. B., & Knoll, A. H.. The Vendian record of Sr and C isotopic variations in seawater: implications for tectonics and paleoclimate. Earth and Planetary Science Letters, 120(3-4), 409-430. (1993).

Kennedy, M. J.. Stratigraphy, sedimentology, and isotopic geochemistry of Australian Neoproterozoic postglacial cap dolostones; deglaciation, delta 13 C excursions, and carbonate precipitation. Journal of sedimentary Research, 66(6), 1050-1064. (1996).

Kirschvink, J. L., & Schopf, J. W.. Late Proterozoic low-latitude global glaciation: the snowball Earth. The proterozoic biosphere, 52, 51-52. (1992).

Komiya, T., Hirata, T., Kitajima, K., Yamamoto, S., Shibuya, T., Sawaki, Y., ... & Han, J.. Evolution of the composition of seawater through geologic time, and its influence on the evolution of life. Gondwana Research, 14(1-2), 159-174. (2008).

Komiya, T., Suga, A., Ohno, T., Han, J., Guo, J., Yamamoto, S., ... & Li, Y.. Ca isotopic compositions of dolomite, phosphorite and the oldest animal embryo fossils from the Neoproterozoic in Weng'an, South China. Gondwana Research, 14(1-2), 209-218. (2008).

Kouketsu, Y., Mizukami, T., Mori, H., Endo, S., Aoya, M., Hara, H., ... & Wallis, S.. A new approach to develop the R aman carbonaceous material geothermometer for low‐grade metamorphism using peak width. Island Arc, 23(1), 33-50. (2014).

Krabbenhöft, A., Fietzke, J., Eisenhauer, A., Liebetrau, V., Böhm, F., & Vollstaedt, H.. Determination of radiogenic and stable strontium isotope ratios (87 Sr/86 Sr; δ 88/86 Sr) by thermal ionization mass spectrometry applying an 87 Sr/84 Sr double spike. Journal of Analytical Atomic Spectrometry, 24(9), 1267-1271. (2009)

Lemarchand, D., Wasserburg, G. J., & Papanastassiou, D. A.. Rate-controlled calcium isotope fractionation in synthetic calcite. Geochimica et cosmochimica acta, 68(22), 4665-4678. (2004).

Lin, S. S., You, C. F., Chung, C. H., Huang, K. F., & Zhou, C.. Mg and Sr Isotopes in Cap Dolostone: Implications for Oceanic Mixing after a Neoproterozoic Snowball Earth Event. Water, 15(15), 2688. (2023).

Liu, C., Wang, Z., & Raub, T. D.. Geochemical constraints on the origin of Marinoan cap dolostones from Nuccaleena Formation, South Australia. Chemical Geology, 351, 95-104. (2013).

Liu, H. C., Chung, C. H., You, C. F., & Chiang, Y. H.. Determination of Sr/Sr and δSr ratios in plant materials using MC-ICP-MS. Analytical & Bioanalytical Chemistry, 408(2). (2016).

Liu, H. C., Hsieh, J. Y., Chen, Y. H., You, C. F., Jiang, W. T., & Wen, H. Y.. Adsorption and desorption behaviors of Sr on montmorillonite: A triple Sr isotope perspective. ACS Earth and Space Chemistry, 6(9), 2250-2260. (2022).

Liu, H. C., Lin, Y. C., Chen, Y. H., Li, M. X., You, C. F., Huang, K. F., ... & Chao, H. C.. Carbonate precipitation-derived CO2 outgassing offsets the mineral weathering sink in the orogenic regime of southwestern Taiwan: Insights from triple Sr isotopes. Science of The Total Environment, 956, 177370. (2024).

Liu, H. C., You, C. F., Huang, K. F., & Chung, C. H.. Precise determination of triple Sr isotopes (δ87Sr and δ88Sr) using MC-ICP-MS. Talanta, 88, 338-344. (2012).

Lv, Y., Liu, S. A., Wu, H., Hohl, S. V., Chen, S., & Li, S.. Zn-Sr isotope records of the Ediacaran Doushantuo Formation in South China: diagenesis assessment and implications. Geochimica et Cosmochimica Acta, 239, 330-345. (2018).

McArthur J.M.. Strontium isotope stratigraphy. In: Application of Modern Stratigraphic Techniques: Theory and Case Histories. Ratcliffe K.T. and Zaitlin B.A. (eds); SEPM Special Publication No. 94. SEPM (Society for Sedimentary Geology), 129–142. (2010).

Narbonne, G. M.. The Ediacara biota: Neoproterozoic origin of animals and their ecosystems. Annu. Rev. Earth Planet. Sci., 33(1), 421-442. (2005).

Nier, A. O.. The isotopic constitution of strontium, barium, bismuth, thallium and mercury. Physical Review, 54(4), 275. (1938).

Ning, M., Yang, F., Ma, H., Lang, X., & Shen, B.. Precipitation of Marinoan cap carbonate from Mn-enriched seawater. Earth-Science Reviews, 218, 103666. (2021).

Nogueira, A. C. R., Riccomini, C., Sial, A. N., Moura, C. A. V., & Fairchild, T. R.. Soft-sediment deformation at the base of the Neoproterozoic Puga cap carbonate (southwestern Amazon craton, Brazil): confirmation of rapid icehouse to greenhouse transition in snowball Earth. Geology, 31(7), 613-616. (2003).

Ohno, T., Komiya, T., Ueno, Y., Hirata, T., & Maruyama, S.. Determination of Sr-88/Sr-86 mass-dependent isotopic and radiogenic isotope variation of Sr-87/Sr-86 in the Neoproterozoic Doushantuo Formation. GONDWANA RESEARCH, 14(1-2), 126-133. (2008).

Pasteris, J. D., & Wopenka, B.. Raman spectra of graphite as indicators of degree of metamorphism. The Canadian Mineralogist, 29(1), 1-9. (1991).

Pin, C., & Bassin, C.. Evaluation of a strontium-specific extraction chromatographic method for isotopic analysis in geological materials. Analytica Chimica Acta, 269(2), 249-255. (1992).

Pu, J. P., Bowring, S. A., Ramezani, J., Myrow, P., Raub, T. D., Landing, E., ... & Macdonald, F. A.. Dodging snowballs: Geochronology of the Gaskiers glaciation and the first appearance of the Ediacaran biota. Geology, 44(11), 955-958. (2016).

Sawaki, Y., Ohno, T., Tahata, M., Komiya, T., Hirata, T., Maruyama, S., ... & Li, Y.. The Ediacaran radiogenic Sr isotope excursion in the Doushantuo Formation in the three Gorges area, South China. Precambrian Research, 176(1-4), 46-64. (2010).

Squire, R. J., Campbell, I. H., Allen, C. M., & Wilson, C. J.. Did the Transgondwanan Supermountain trigger the explosive radiation of animals on Earth?. Earth and Planetary Science Letters, 250(1-2), 116-133. (2006).

Wu, N., Zhang, J., Mao, H., Zhang, G., & Zhao, Z.. Geochemical behavior of stable strontium isotopes during continental weathering process: A review. Geosystems and Geoenvironment, 3(2), 100144. (2024).

Xiao, S., Bao, H., Wang, H., Kaufman, A. J., Zhou, C., Li, G., ... & Ling, H.. The Neoproterozoic Quruqtagh Group in eastern Chinese Tianshan: evidence for a post-Marinoan glaciation. Precambrian Research, 130(1-4), 1-26. (2004).

Jiedong, Y., Weiguo, S., Zongzhe, W., Yaosong, X., & Xiancong, T.. Variations in Sr and C isotopes and Ce anomalies in successions from China: evidence for the oxygenation of Neoproterozoic seawater?. Precambrian Research, 93(2-3), 215-233. (1999).

Zhao, Y. Y., Zheng, Y. F., & Chen, F.. Trace element and strontium isotope constraints on sedimentary environment of Ediacaran carbonates in southern Anhui, South China. Chemical Geology, 265(3-4), 345-362. (2009).