利用非傳統穩定同位素探討前寒武紀/寒武紀過渡期之古環境變化(III)

科技部補助專題研究計畫報告

利用非傳統穩定同位素探討前寒武紀/寒武紀過渡期之古環境變

化(III)

報 告 類 別 ： 成果報告 計 畫 類 別 ： 個別型計畫 計 畫 編 號 ： MOST 108-2116-M-006-011-執 行 期 間 ： 108年08月01日至109年07月31日 執 行 單 位 ： 國立成功大學地球科學系（所） 計 畫 主 持 人 ： 游鎮烽 計畫參與人員： 學士級-專任助理：程安琪 碩士班研究生-兼任助理：陳宜琪 碩士班研究生-兼任助理：陳瑋晨 碩士班研究生-兼任助理：陳柏達 碩士班研究生-兼任助理：許哲維 碩士班研究生-兼任助理：洪清宏 博士班研究生-兼任助理：林彥伯 博士後研究-博士後研究：劉厚均 報 告 附 件 ： 出席國際學術會議心得報告

本研究具有政策應用參考價值：■否　□是，建議提供機關

（勾選「是」者，請列舉建議可提供施政參考之業務主管機關）

本研究具影響公共利益之重大發現：□否　□是　

中　華　民　國　109　年　10　月　28　日

中 文 摘 要 ： 中文摘要及關鍵詞: 地球歷史與生命演化有著緊密的關聯性。地表環境變遷將導 致適合者生存。遠古宙至早顯生宙地層，介於埃迪卡拉和寒武紀過 渡帶岩層，記錄著雪球地球時期劇烈氣候、環境和生物演化資訊。 為研究相關地層，我們組成國際研究團隊(中、台、蘇和美國)，進 行合作研究，預期可產生整合資料，提供關於埃迪卡拉雪球地球和 早期生命演化的相關過程。此團隊已利用雷射剝蝕及nanoSIMS進行 定年，證實碎屑礦物對定年結果有關鍵影響。初步年代資料顯示詳 細微區觀測是礦物標地定年重要前置工作；已有二篇相關文章收錄 於2019 PC-C Phosphogenic Event ”前寒武紀研究”專刊(發表中 )。 108年度為延續性計畫的第四年，我們已參與兩屆「寒武紀/前寒武 紀過渡帶」於中國科技大學及美國UCLA舉辦聯合會議，並前往貴州 省貴陽和甕安等地野外勘查，採得珍貴含磷標本，利用東京大學或 地科所NanoSIMS，對磷灰石及磷釔礦、獨居石和鋯石進行微區U-Pb定年，目前已針對微區礦物中硫同位素、REEs及微量元素進行初 步評估，並部分完成XRF、XRD和拉曼光譜等觀察；109年將挑選重要 碳酸鹽或磷酸鹽樣品，進行細部硼濃度及硼同位素研究系統性工作 等，包括微礦物鑽取粉末、酸鹼液溶解、樹栺分離及MCICP-MS, 配 合本研究室新創硼同位素分析技術(Wang et al., 2015; Wang et al., 2020), 將可逐步解開寒武紀/前寒武紀過渡帶海水酸鹼值環境 演化歷程及可能控制因素或成岩作用修正有初步掌控。

中 文 關 鍵 詞 ： 中文關鍵詞:

雪球地球,海洋酸化,藍田/甕安微化石區,同位素 英 文 摘 要 ： Abstract and keywords:

Earth’s history and the evolution of life are closely interconnected. Changes in the ambient environment lead to selection of organisms best able to cope with the new settings. We have established an international-team,

including scientists from China, Taiwan, Russia and USA to tackle various issues in Precambrian/Cambrian transition period. We have been assigned to focus on developing proper U-Pb dating technique for apatite grains or other

authigenic minerals, as well as other redox sensitive isotopes in the Neoproterozoic Doushantuo and Lantian Formation, South China. These results will be published in a “PC-C Phosphogenic Event” special publications in a top-journal in this field in 2020, Precambrian Research. This is a continuous of the “Precambrian/Cambrian

Transition Zone Study”, we will examine in details of the phosphorites from the Doushantuo and Lantian Formation. Our preliminary SEM studies have documented the occurrence of numerous minerals suitable for U-Pb dating. Initial results using Electron Probe and LA-ICPMS analyses have also

identified secondarily emplaced detrital minerals (e.g., zircon) that on the bases of their morphology and chemistry

can be excluded from the micro-mineral age determinations. On the other hand, our studies will also focus step-by-step on environmental proxies, including B isotopes (for oceanic pH), S (for biogeochemical cycling), Mo-V-U (for redox and oxygenation conditions), Sr-Ca-Mg isotopes(for continental weathering), as well as stable C, N and O isotopes (for carbon sources and productivity). This year we will focus on our efforts to analyze various B and B isotopes in carbonates or phosphorites collected for a better

understanding of the phosphorite specimens, in terms of the biogeochemical cycling of B and 11B recorded in the

Neoproterozoic Doushantuo and Lantian Formation. A new sensitive MCICP-MC technique for B isotopic analyses,

developed in our lab (Wang et al., 2012; Wang et al., 2020) will be applied to reconstruct marine pH environmental changes recorded in Lantian or Weng’an strata on the Snowball Earth. Our international team will use state-of-the-art techniques to provide new telling data about the evolution of life and the oceanic environment changes on the Snowball Earth period.

英 文 關 鍵 詞 ： Keywords:

Snowball Earth, Ocean acidification, Lantian/Weng’an micro-fossils, isotopes

科技部補助專題研究計畫成果報告

（□期中進度報告/□期末報告）

（計畫名稱）

計畫類別：□個別型計畫 □整合型計畫

計畫編號：MOST108－2116－M－006－011－

執行期間：108 年 08 月 01 日至 109 年 07 月 30 日

執行機構及系所：國立成功大學地球科學系

計畫主持人：游鎮烽

共同主持人：

計畫參與人員：劉厚均、程安琪

本計畫除繳交成果報告外，另含下列出國報告，共 _2_ 份：

□執行國際合作與移地研究心得報告

▓出席國際學術會議心得報告

□出國參訪及考察心得報告

本研究

具有政策應用參考價值：

▓否 □是，建議提供機關_______

(勾選「是」者，請列舉建議可提供施政參考之業務主管機關)

本研究具影響公共利益之重大發現：▓否 □是

中 華 民 國 109 年 10 月 01 日

附件一

中文摘要及關鍵詞: 地球歷史與生命演化有著緊密的關聯性。地表環境變遷將導致適合者生存。遠古宙至早顯生宙地 層，介於埃迪卡拉和寒武紀過渡帶岩層，記錄著雪球地球時期劇烈氣候、環境和生物演化資訊。為研 究相關地層，我們組成國際研究團隊(中、台、蘇和美國)，進行合作研究，預期可產生整合資料，提 供關於埃迪卡拉雪球地球和早期生命演化的相關過程。此團隊已利用雷射剝蝕及nanoSIMS進行定年， 證實碎屑礦物對定年結果有關鍵影響。初步年代資料顯示詳細微區觀測是礦物標地定年重要前置工 作；已有二篇相關文章收錄於2019 PC-C Phosphogenic Event ”前寒武紀研究”專刊(發表中)。 108年度為延續性計畫的第四年，我們已參與兩屆「寒武紀/前寒武紀過渡帶」於中國科技大學及美國 UCLA舉辦聯合會議，並前往貴州省貴陽和甕安等地野外勘查，採得珍貴含磷標本，利用東京大學或地 科所NanoSIMS，對磷灰石及磷釔礦、獨居石和鋯石進行微區U-Pb定年，目前已針對微區礦物中硫同位 素、REEs及微量元素進行初步評估，並部分完成XRF、XRD和拉曼光譜等觀察；109年將挑選重要碳酸鹽 或磷酸鹽樣品，進行細部硼濃度及硼同位素研究系統性工作等，包括微礦物鑽取粉末、酸鹼液溶解、 樹栺分離及MCICP-MS, 配合本研究室新創硼同位素分析技術(Wang et al., 2015; Wang et al., 2020), 將可逐步解開寒武紀/前寒武紀過渡帶海水酸鹼值環境演化歷程及可能控制因素或成岩作用修正有初 步掌控。

中文關鍵詞:

Abstract and keywords:

Earth’s history and the evolution of life are closely interconnected. Changes in the ambient environment lead to selection of organisms best able to cope with the new settings. We have established an international-team, including scientists from China, Taiwan, Russia and USA to tackle various issues in Precambrian/Cambrian transition period. We have been assigned to focus on developing proper U-Pb dating technique for apatite grains or other authigenic minerals, as well as other redox sensitive isotopes in the Neoproterozoic Doushantuo and Lantian Formation, South China. These results will be published in a “PC-C Phosphogenic Event” special publications in a top-journal in this field in 2020, Precambrian Research.

This is a continuous of the “Precambrian/Cambrian Transition Zone Study”, we will examine in details of the phosphorites from the Doushantuo and Lantian Formation. Our preliminary SEM studies have documented the occurrence of numerous minerals suitable for U-Pb dating. Initial results using Electron Probe and LA-ICPMS analyses have also identified secondarily emplaced detrital minerals (e.g., zircon) that on the bases of their morphology and chemistry can be excluded from the micro-mineral age determinations. On the other hand, our studies will also focus step-by-step on environmental proxies, including B isotopes (for oceanic pH), S (for biogeochemical cycling), Mo-V-U (for redox and oxygenation conditions), Sr-Ca-Mg isotopes(for continental weathering), as well as stable C, N and O isotopes (for carbon sources and productivity). This year we will focus on our efforts to analyze various B and B isotopes in carbonates or phosphorites collected for a better understanding of the phosphorite specimens, in terms of the biogeochemical cycling of B and 11B recorded in the Neoproterozoic Doushantuo and Lantian Formation. A new sensitive MCICP-MC technique for B isotopic analyses, developed in our lab (Wang et al., 2012; Wang et al., 2020) will be applied to reconstruct marine pH environmental changes recorded in Lantian or Weng’an strata on the Snowball Earth. Our international team will use state-of-the-art techniques to provide new telling data about the evolution of life and the oceanic environment changes on the Snowball Earth period.

Keywords:

報告內容：包括前言、研究目的、文獻探討、研究方法、結果與討論（含結論與建議、執行計畫過程 遇到之困難或阻礙）等。 本計畫已充分應用國立成功大學和中研院地科所的精密同位素質譜儀等分析工具，發展原位微區 化學及同位素精確測量及鈾-鉛定年技術，結合日本、中國、蘇聯和美國等國際知名跨領域專家緊密合 作，可產生整合資料，提供關於埃迪卡拉雪球地球、海洋環境和早期生命快速分異演化過程，今年已 發表三篇重要科學文章於國際著名學術期刊。

Introduction

Sedimentary rocks record wealth of information on the evolution of lithosphere, hydrosphere,

atmosphere and biosphere. However, uncertainty about the age of many Precambrian sequences makes it very difficult to establish the accurate temporal framework which can dramatically improve our understanding of the scale and duration of geological and biological events. The ages of sedimentary formations especially in the Phanerozoic period are conventionally estimated from chemo-or biostratigraphy correlation. In older rocks, the age determination using this method become inapplicable due to the absent of fossil records. Some

indirect methods, such as dating of contemporaneous volcanic rocks, bracketing relationships of igneous and metamorphic rocks, and the dating of detrital and diagenetic minerals (Rasmussen 2005), can be used to constrain the age of sedimentary rocks. But many basins lack suitable volcanic rocks and sometimes the range of constrained ages can be up to hundreds of millions of years. Dating detrital minerals shows very limited information about the depositional age since it can only yield maximum ages. Most diagenetic minerals form in low temperature environment and have low closure temperature, making them prone to later thermal resetting, therefore are not suitable for geochronology. A recent development in sedimentary geochronology has been the identification of the U–Pb chronometer, xenotime, as a diagenetic phase in sedimentary rocks (Rasmussen 1996; Rasmussen et al. 1998). Using a SIMS with 5–10 μm spatial resolution, it is now possible to date xenotime, yielding precise dates that in some instances approximate the age of deposition

(McNaughton et al. 1999; Vallini et al. 2002; Rasmussen et al. 2004). Being a common U-bearing accessory mineral in sedimentary rocks, U–Pb and dating of apatite has potential application in sedimentary provenance studies. Apatite has been widely used in thermochronology studies (Chew & Spikings 2015). The high closure temperature of ca. 450-550 °C (Chamberlain & Bowring 2001; Schoene & Bowring 2007) makes U-Pb apatite system a useful tool to study the deposition ages of sedimentary or low-grade meta-sedimentary rocks. Apatite is also a relatively common diagenetic mineral, and is the main phase in phosphorite deposits where it occurs as cryptocrystalline aggregates (Follmi 1996). The uranium and lead isotope of apatite has been

measured by isotope dilution mass spectrometry (Oosthuyzen & Burger 1973; Romer 1996; Corfu & Stone 1998), ion microprobe (Li et al. 2012; Sano, Oyama, et al. 1999; Sano, Terada, et al. 1999) and laser

ablation-inductively coupled plasma-mass spectrometry (Thomson et al. 2012; Willigers et al. 2002). The primary limitation of U-Pb apatite geochronology is poor dating precision cause by low U concentration and

high common lead content.

The Ediacaran marks the final geological period of the Proterozoic eon between the termination of the global Marinoan glaciation at ∼635 Ma and the beginning of the Cambrian at 542 Ma. The Ediacaran Earth experienced major biological changes, including radiation of complex multicellular life such as globally distributed Ediacaran-type soft-bodied animals. The Neoproterozoic Doushantuo and Lantian Formation, South China, preserve unique assemblages of early multicellular fossils and overlies rocks, which are thought to have formed during an ice age of global extent. The age of these formations are thus critical for

understanding the important biological and climatic events that occurred towards the end of the Proterozoic Eon.

Geological setting and previous works The Doushantuo Formation is a recently discovered lagerstätte in Guizhou Province, China that is most notable for its scientific contributions in the hunt for Precambrian life. Doushantuo is of particular interest because its fossils, dating from about 565 to 590 million years ago, predate the Cambrian Explosion by at least 20 million years. The most fossiliferous zones are estimated to be 570 million years old. The Doushantuo Formation is represented by a phosphate-dolostone sequence at

Weng'an, where it is 33 to 55 m thick and consists mainly of dark phosphate, cherty phosphate, chert, and gray dolomite. The overlying Dengying Formation, of Ediacaran (~565 Ma to 544 Ma) age and containing rare Ediacaran body fossils in the lower part and basal Cambrian shelly fossils near the top, is a 180 m thick dolomite sequence. The Doushantuo Formation is further divided into 4 Members in ascending order: Member 1 (cap carbonate), Member 2 (an alternating shale-mudstone-dolostone sequence), Member 3 (dolostone-and limestone-dominated), Member 4 (also called the Miaohe Member black shale)(Wang et al. 1998; Zhu et al. 2003; Sawaki et al. 2010).

The Lantian formation is a 150-meter-thick sequence of rocks deposited in southern China during a 90-million-year epoch in the Ediacaran period. Its algal macrofossils (which have alternatively been

interpreted as putative metazoans are the oldest large and complex fossils known (Yuan et al. 2011). The rocks were deposited in shallow seas, in the photic zone yet below storm wave base yet were deposited in

predominantly anoxic conditions. The Lantian Formation is divided into four members that are similar to and can be correlated with the four divisions of the Doushantuo Formation(McFadden et al. 2009). The lowest Member I is a 1.8-m-thick dolostone conformably overlying a Marinoan-age glacial diamictite. The overlying

Membethe Doushantuo Formation(McFadden et al. 2009). The lowest Member I is a 1.8-m-thick dolostone conformably overlying a Marinoan-age glacial diamictite. The overlying Member II consists of 35 m of finely laminated fossiliferous black shales. Member III is 34 m thick and characterized by dolostones interbedded with mudstones in the lower part and ribbon rocks in the upper part. The uppermost Member IV consists of 20m of black silty mudstones, which is overlain by siliceous rocks of the Piyuancun Formation and then the early Cambrian Hetang Formation (Yuan et al. 2002). The stratigraphic relations of Doushantuo Formation and Lantian Formation are shown in Fig 1.

Fig. 1 Stratigraphic relations of Doushantuo Formation and Lantian Formation

Precise zircon U–Pb dating of volcanic tuff beds from the lower and uppermost Doushantuo Formation has constrained the age of the Doushantuo Formation to between 635.2±0.6 and 551.1±0.7 Ma(Condon et al. 2005). The Re–Os age for the base of Doushantuo Member 4 has been determined to be 591.1±5.3 Ma (Zhu et al. 2013). Dating of Doushantuo phosphorites by a Lu-Hf dating method and Pb-Pb geochronometry

independently yield ages of 584±26 Ma and 599.3±4.2 Ma, respectively (Barfod et al. 2002). Pb isotopic composition analysis of Doushantuo black shales yield a Pb isotope isochron ages of 572±36Ma (Chen et al. 2009). No radiometric ages are available to directly constrain the depositional age of the Lantian Formation.

However, lithostratigraphic and chemostratigraphic correlation between the Lantian Formation and the Doushantuo Formation in the Yangtze Gorges area (Zhou & Xiao 2007; Zhu et al. 2007; Wang et al. 2014) indicates that the fossiliferous Member II is between 635 Ma and 576 Ma(Yuan et al. 2011). Yangtze Gorges area (Zhou & Xiao 2007; Zhu et al. 2007; Wang et al. 2014) indicates that the fossiliferous Member II is between 635 Ma and 576 Ma(Yuan et al. 2011).

Scope of research project

The overall purpose of this is to determine the deposition age of Neoproterozoic Lantian and Doushantuo Formations in Yangtze Block using apatite U-Pb dating method. These results will help us to reconstruction the oxygenation events of Ediacaran Ocean. We hope to address the following research topics:

What are the deposition ages of Lantian and Doushantuo Formation?

Assess the criteria for preparing adequate specimens for nanoSIMS analysis Characterized a xenotime standard for SIMS and LA-ICPMS measurements.

What does the paleo-environment reconstruction tell us about the changes in the Ediacaran ocean and atmosphere?

Methodology Dating diagenesis

The feasibility of the radiometric dating methods for diagenesis were established with Ar-Ar age of glauconies (Smith et al. 1993), Rb-Sr age of illite (Morton 1985), K-Ar age of diagenetic K-feldspar (Girard et al. 1988), Pb-Pb age of monazite nodules (Evans et al. 2002) and U-Pb age of apatite (Chandler & Parrish 1989). A recent development in sedimentary geochronology has been the identification of the U–Pb

chronometer, xenotime, as a diagenetic phase in sedimentary rocks (Fletcher et al. 2000; Rasmussen et al. 2004; Rasmussen 2005). A variety of methods are currently available for U-Pb geochronology of diagenetic minerals. Three main techniques used are TIMS, SIMS and MC-ICPMS. Using an ion microprobe (Sano, Oyama, et al. 1999) or LA-ICPMS (Willigers et al. 2002; Chew et al. 2011) , it is possible to date xenotime and apatite with a spatial resolution of 5-30μm. Isotope dilution TIMS involves the chemical digestion of entire crystals and is more precise than in situ methods. However, heterogeneity and small sizes which are

typical characteristics of diagenetic minerals make the microprobe techniques more appropriate. Under ideal conditions, the LA-ICPMS can yield U–Pb ages that approach the accuracy and precision delivered by SIMS in a fraction of the time with the cost of much larger sample consumption. Analysis by ion microprobe is the primary method used in this study because of the fine spatial resolution, shallow penetration depth and high precision. SIMS in a fraction of the time with the cost of much larger sample consumption. Analysis by ion microprobe is the primary method used in this study because of the fine spatial resolution, shallow penetration depth and high precision.

SIMS U-Pb geochronology

In situ dating using high spatial resolution SIMS is a powerful technique to acquire valuable ages

information from apatite or xenotime. In SIMS analysis, a primary ion beam of O -or O2-bombard the sample, sputtering the surface of specimen and analyzing ejected secondary ions. The generated secondary ions are focused and transferred to mass spectrometer, filtered according to their energy distributions, separated by mass to charge ratios and detected using low noise ion counter. Precision and accuracy in SIMS U-Pb geochronology strongly depend on the method of determination of the inter-element ion ratios from the measured secondary ion ratios (Jeon & Whitehouse 2015). Therefore, a well-characterized matrix-matched standard to correct for elemental fractionation is crucial. Also, the low U contents of apatite which limited production of radiogenic Pb may hinder the attempts to apply in situ SIMS U-Pb technique. The intensity of 204Pb needs to be accurately measured to ensure robust common lead correction.

Work items finished in 2019 (III):

a. To write up two manuscripts for the 2019 Precambrian Research special publication proposed by PC/P international team and edited by Schopf et al. (2019);

b. To test run MC-ICP-MS method (Das et al., 2012) for the available Doushantuo phosphorites or Lantain black shale specimens;

c. To trace the potential P source in the shallow water zone of the outer shelf sedimentary environment, i.e. either continental sources, or upwelled bottom water masses, using radiogenic Sr isotopic ratios from the Weng'an phosphorite.

d. To understand the redox conditions and transitional processes near Precambrian/Cambrian boundary using newly developed 238U/235U isotopic approach, coupled with other redox sensitive elemental

concentration (i.e. U, V, Mo and S) or isotopic indicators (i.e. S and Mo isotopes) from the Weng'an phosphorites.

e. A preliminary leaching experiments of B carbonate and phorphorites in the CYD specimens;

f. Educate 1 PhD and 2 Master students in high precision isotopic measurements;

g. Train a Postdoctoral fellow in high precision isotopic measurements;

h. Publish 3 SCI papers in international journals;

i. Gain a better understanding of S, U and Sr isotopic geochemical cycle in the ocean during

Precambrian/ Cambrian transition period. Preliminary results of B concentration in CYD specimens after carbonates removal and a series of leaching procedures.

科技部補助專題研究計畫成果彙整表

計畫主持人：游鎮烽 計畫編號：MOST 108-2116-M-006-011 計畫名稱：利用非傳統穩定同位素探討前寒武紀/寒武紀過渡期之古環境變化(III) 成果項目 量化 單位 質化 （說明：各成果項目請附佐 證資料或細項說明，如期刊 名稱、年份、卷期、起訖頁 數、證號...等） 國 內 學術性論文 期刊論文 篇 請附期刊資訊。 研討會論文 專書 本 請附專書資訊。 專書論文 章 請附專書論文資訊。 技術報告 篇 其他 篇 國 外 學術性論文 期刊論文 3 篇

Chung et al., (2019) (in press, Precambrian Research) Liu et al. (2019) (in press

Precambrian Research) Wang et al. (2020) Microchemical Journal 152, 104424 , 研討會論文 專書 本 請附專書資訊。 專書論文 章 請附專書論文資訊。 技術報告 篇 其他 篇 參 與 計 畫 人 力 本國籍 大專生 人次 請填寫依「科技部補助專題 研究計畫約用研究人力注 意事項」所實際約用專任、 兼任人員。 碩士生 3 博士生 1 專任人員(博士級) 專任人員(非博士級) 非本國籍 大專生 碩士生 博士生 專任人員(博士級) 專任人員(非博士級) 其他成果 (無法以量化表達之成果如辦理學術活動、獲得獎項、 重要國際合作、研究成果國際影響力及其他協助產業 技術發展之具體效益事項等，請以文字敘述填列。) 附件三

科技部補助專題研究計畫出席國際學術會議心得報告

日期： 年 月 日

計畫編號

MOST 108－2116－M－006－011－

計畫名稱

利用非傳統穩定同位素探討前寒武紀/寒武紀過渡期之古環境變化

(III)

出國人員

姓名

劉厚均

服務機構

及職稱

國立成功大學地球科學系

會議時間

2020 年 06 月 21 日

至 2020 年 06 月 26 日

會議地點

虛擬會議（原：夏威夷舉

行）

會議名稱

(中文) Goldschmidt 2020 虛擬會議

(英文) Goldschmidt Virtual 2020

發表題目

(中文) 以實驗室實驗評估黏土礦物吸附對穩定鍶同位素的分化行為

(英文) Stable Sr Isotope Fractionation between Fluids and Clay

Minerals: Insight from Laboratory Batch Experiments

2

一、 參加會議經過

Goldschmidt Conference 為地球化學領域最重要的年度研討會，常年在世界各大城市巡迴舉 辦，為該領域學術交流最佳的機會與場域。今年適逢 Covid-19 疫情的影響，首次改以虛擬會議 的方式舉行，取消原定在夏威夷舉辦的實體會議。因此，會議的內容改以線上發佈海報、投影 片或是影片等方式來呈現，讓與會者可以在約一週的時間內先自由觀看內容。至於，交流的方 式，主辦單位給予制定的時間表，讓發表者在線上等候以線上提問與回答的方式進行。會議相 關的工作坊，則改成透過線上平台如：Zoom 的會議室來進行。

筆者在此次線上虛擬會議，在「Source to sink dynamics of sediment, solutes and carbon: implications for climate, biogeochemical cycles, tectonics and life」議程以發表論文「Stable Sr Isotope Fractionation between Fluids and Clay Minerals: Insight from Laboratory Batch

Experiments」，探討在風化的過程中，黏土礦物的水岩反應（吸脱附作用、置換反應）對於鍶元

素的影響，及其可能的穩定鍶同位素組成的分化，對於 critical zone 的風化作用與影響同位素的 分化機制做出更近一步的討論。同時，地球化學領域相關的研究，近年日益重視化學數據與數 值模擬、模型，以相輔相成的方式，來進行數據探討。這種多維的驗證，可以對於數據觀察與 推導能有更嚴謹的約束。因此，筆者也在此次的會議中參與「Reactive transport model」的工作 坊及相關軟體的訓練。透過這次連續 4 天每天線上 4-5 個小時的研討與實作訓練，筆者對於 Reactive transport model 的理論基礎、概念、及軟體實作都已有了初步的認識。目前也已經將相 關的軟體及模型做初步的修改，實際應用於筆者的研究當中，可說收獲相當豐厚。

此次會議首次改採線上的方式進行，改變了相關領域學者參與研討會與交流的方式。筆者 認為，數位方式可以觸及的內容變多了；但是，由於時差因素以及安排 QA 的時間過短，討論及 交流可能無法有過去現場臨場的效率及較果，實屬可惜。

二、 與會心得

筆者的研究屬性偏向於關鍵帶的化學風化作用，實屬「Earth surface processes from chemical

fronts to climate change（地表作用：從化學前緣到氣候變遷）」領域。這是此次 Goldschmidt 會

議中 17 個領域的其中之一。今年的議題偏向於欲了解調節全球氣候變遷的機制與過程，必須針 對塑造地表的作用、物質的傳輸過程（源匯）及關鍵帶的生地化作用作深入的探討，尤其是這 些作用對於關鍵帶的生物地球化學過程相當敏感，議會影響未來的氣候動態。因此，在子項目 中，在物理剝蝕和化學風化相關的研究，今年特別強調以新技術的輔助或是實驗室的模擬實驗 來示蹤沈積物或是風化的來源，或是釐清在關鍵帶的相關控制機制，成為源匯研究的一大亮 點：像是以筆者以δ88/86_{Sr 輔助傳統}87_Sr/86_{Sr 來示蹤水岩交換過程對於 Sr 的循環，探索對於 Sr}

budget 的影響。UC Berkeley 的團隊以 Uranium-series comminution age（UCA）技術來量化與喜 馬拉雅山隆升和快速侵蝕相關的大規模泥沙運移，主張喜馬拉雅山是現代地球上最大且最重要 的沈積物源之一。另外，過去通常假設在源匯的傳輸過程中，風化作用通常發生在山坡上。但 是在活躍造山帶上，高侵蝕率減少了礦物在山坡上的駐留時間，從而將大量未風化的沉積物輸 送到河道。雖然河流可能是風化的熱點，沈積物運輸過程中的顆粒磨損會增加礦物的表面積並 加快反應速度，但是相關對於化學風化的影響有待評估。以內華達大學及哈佛大學為首的團 隊，透過嘗試使用環形水槽實驗來量化河流沉積物的磨損如何增加化學風化。成果顯示跟岩性 有關，以玄武岩為例化學風化速率可加速 1.6 倍以上。沖積河流是調節山脈、森林、低地與海 洋間顆粒有機碳（POC）傳輸通量的關鍵角色。河流中沈積物的傳輸是影響最終 POC 成為大氣

CO2的碳源亦或是碳匯。因此，沈積物的傳輸模式扮演關鍵角色。以德國波茨坦地球科學研究

中心為首的團隊，主張沖積平原區河水 POC 的 C-14 變化不是受控於來源，而是沈積物傳輸的

動力學造成 POC 的轉化而導致，從而推論沈積物的傳輸方式造成 POC 造成影響大氣 CO2通

量。此外，本屆研討會中，亦有多項論文重新審視元素的循環及相關的源匯模型，如：黏土礦 物影響海洋的 B 通量（成大）、硫酸鹽氧化還原過程影響河水 S 的通量（UCLA）等。

另一方面，攸關近年來 Reactive transport model 對於關鍵帶的風化研究日益重要。已有相當 多的研究將此模型應用於土壤風化、地下水逕流溶解物質傳輸、河川風化、水岩反應等研究項 目中。透過實際的化學、物理觀測數據，結合 Reactive transport model 的計算，約束與驗證理論 模型。因此，筆者也藉由這次的研討會參與 Reactive transport model 的工作坊。在超過 16 個小 時的訓練當中，講師透過 10 個主題的研究實例，講述理論基礎及如何運用套裝軟體

Geochemists’ WorkBench 來計算 Reactive transport model。原定 2 天每天 8 小時的課程，因為疫 情的影響，改為 Zoom 的線上教學。由於時差的關係，將 16 個小時拆成四天，因此有更多的時 間可以實作，再隔天的課程中進行反饋。因此，筆者覺得效果比濃縮在 2 天的密集課程，無論 是知識的理解吸收或是更多的問題討論，都來得更加熱絡。也是基於如此，筆者有更多的時間 將案例教學修改成應用於自身相關的研究，同時也跟講師有更密切的討論與互動，可謂獲益良 多。

三、 發表論文全文或摘要

Stable Sr isotope fractionation between fluids and clay minerals: Insight from

laboratory batch experiments

HOU-CHUN LIU1_{,* AND CHEN-FENG YOU}1

1_{Department of Earth Sciences, National Cheng Kung University, Tainan 70101, Taiwan}

*correspondence: [email protected]

Preferential removal of isotopically lighter Sr from aqueous phases by adsorption onto phyllosilicate clay minerals and iron oxides have been observed in many catchment studies. However, at this stage, it is not straightforward to assess the effect of the adsorption process on Sr isotope fractionation through field studies because the fractionation may be attributed to multiple factors. To better constrain the adsorption process on exogenic Sr cycling, a time-series monitoring of laboratory batch experiment (from 0 to 24 hours) was conducted at 25°C and a pH of ~5 to evaluate the possible Sr isotope fractionation during the adsorption/desorption processes onto/from phyllosilicate clay minerals. Experiments showed that isotopically heavier Sr was preferentially released from smectite during the extraction experiments (Δ88/86_{Sr could be as large as 0.20‰); in contrast, isotopically lighter Sr was preferentially adsorbed onto}

smectite during the adsorption processes (Δ88/86_{Sr could be up to 0.17‰).} 87_Sr/86_{Sr data indicates that the}

exchange of Sr, between the aqueous phase and the mineral phase, reaches equilibrium in less than 30 mins. After equilibrium, lighter Sr isotopes were adsorbed onto smectite and the size of fractionation (Δ88/86_Sr

fluid, initial-final) attained constant values of - 0.16‰±0.03‰. This size is comparable with the

Δ88/86_Sr

4

ignored in the catchment scale. This study demonstrates the potential Sr isotope fractionation caused by adsorption processes on a laboratory scale, a comprehaive evaluation in the field catchments will be explored in future studies.

[1] Liu et al. (2017), Chemical Geology 456, 85-97.

四、建議

無。

五、攜回資料名稱及內容

筆者參加 Reactive transport model 的工作坊，攜回研討會課程講義乙份、Geochemist’ WorkBench V14 案例研究操作指南乙份、及 Geochemist’ WorkBench 案例研究模型 source code 乙批。

六、其他

1

科技部補助專題研究計畫出席國際學術會議心得報告

日期：109 年 07 月 10 日

計畫編號

MOST 108－2116－M－006－011－

計畫名稱

利用非傳統穩定同位素探討前寒武紀/寒武紀過渡期之古環境變

化(III)

出國人員

姓名

游鎮烽

服務機構

及職稱

國立成功大學地球科學系

會議時間

2020 年 06 月

21 日至 2020 年

06 月 26 日

會議地點

虛擬會議（原：夏威夷舉行）

會議名稱

(中文) Goldschmidt 2020 虛擬會議

(英文) Goldschmidt Virtual 2020

發表題目

(中文) 利用陸上和海域泥火山重新評估 B 和δ11_{B 的海洋質量平衡}

(英文) Re-evaluation of B and δ11_{B budgets in the ocean based on mud}

volcanoes on land and offshore 附件五

一、 參加會議經過

Goldschmidt Conference 為地球化學領域最重要的年度研討會，常年在世界各大城市巡 迴舉辦，為該領域學術交流最佳的機會與場域之一。今年適逢 Covid-19 疫情影響，取消原 定在夏威夷舉辦實體會議首次改以虛擬會議的方式舉行。因此，會議內容改以線上發佈海 報、投影片或是影片等方式來呈現，讓與會者可以在約一週的時間內先自由觀看內容。至 於，交流的方式，主辦單位給予制定的時間表，讓發表者在線上等候以線上提問與回答的方 式進行。會議相關的工作坊，則改成透過線上平台如：Zoom 的會議室來進行。

筆者在此次線上虛擬會議有三篇論文在「Source to sink dynamics of sediment, solutes and carbon: implications for climate, biogeochemical cycles, tectonics and life」議程宣讀，分別為 「Re-evaluation of B and δ11_{B budgets in the ocean based on mud volcanoes on land and}

offshore」、「Stable Sr Isotope Fractionation between Fluids and Clay Minerals: Insight from Laboratory Batch Experiments」及「Two-end-member mixing in the fluids emitted from a sediment hosted geothermal system, mud volcano Lei-Gong-Huo, Eastern Taiwan: Evidence from

Sr isotopes」，探討內容包含有「重新評估 B 和δ11B 的海洋質量平衡」「在風化的過程中，黏 土礦物的水岩反應對於鍶元素的影響，及「東台灣雷公火泥火山的混合過程及鍶同位素組成 的變化，對於泥火山的地化作用及風化作用影響同位素的分化機制做出更進一步討論。 此次會議首次改採線上方式進行，改變相關領域學者參與研討會與交流的方式。筆者認 為，數位方式可以觸及的內容變多；但由於時差因素以及安排 QA 的時間過短，討論及交流 可能無法達到過去現場臨場的效率及成果。

3

二、 與會心得

此次與會收穫良多，尤其對博後學者助益更大，劉博士研究屬性偏向於關鍵帶化學風化 作用，實屬「Earth surface processes from chemical fronts to climate change」領域。是此次 Goldschmidt 會議中 17 個領域的其中之一。今年的議題偏向調節全球氣候變遷的機制與過 程，必須針對塑造地表作用、物質傳輸過程及關鍵帶的生地化作用作深入探討，尤其是這 些作用對於關鍵帶的生物地球化學過程相當敏感，議會影響未來氣候動態。因此，在子項 目中，在物理剝蝕和化學風化相關的研究，今年特別強調以新技術的輔助或是實驗室的模 擬實驗來示蹤沈積物或是風化的來源，或是釐清在關鍵帶的相關控制機制，成為源匯研究 的一大亮點，過去通常假設在源匯的傳輸過程中，風化作用通常發生在山坡上。但是在活 躍造山帶上，高侵蝕率減少了礦物在山坡上的駐留時間，從而將大量未風化的沉積物輸送 到河道。雖然河流可能是風化的熱點，沈積物運輸過程中的顆粒磨損會增加礦物的表面積 並加快反應速度。內華達大學及哈佛大學為首的團隊，透過嘗試使用環形水槽實驗來量化 河流沉積物的磨損如何增加化學風化。成果顯示跟岩性有關，以玄武岩為例化學風化速率 可加速 1.6 倍以上。沖積河流是調節山脈、森林、低地與海洋間顆粒有機碳（POC）傳輸通 量的關鍵角色。河流中沈積物的傳輸是影響最終 POC 成為大氣 CO2的碳源亦或是碳匯。因 此，沈積物的傳輸模式扮演關鍵角色。以德國波茨坦地球科學研究中心為首的團隊，主張 沖積平原區河水 POC 的 C-14 變化不是受控於來源，而是沈積物傳輸的動力學造成 POC 的 轉化而導致，從而推論沈積物的傳輸方式造成 POC 造成影響大氣 CO2通量。另一方面，攸

關近年來 Reactive transport model 對於關鍵帶的風化研究日益重要。已有相當多的研究將此 模型應用於土壤風化、地下水逕流溶解物質傳輸、河川風化、水岩反應等研究項目中。透 過實際的化學、物理觀測數據，結合 Reactive transport model 的計算，約束與驗證理論模 型。因此，劉博士也藉由這次的研討會參與 Reactive transport model 工作坊。在超過 16 個 小時的訓練當中，講師透過 10 個主題的研究實例，講述理論基礎及如何運用套裝軟體 Geochemists’ WorkBench 來計算 Reactive transport model。

三、 發表論文全文或摘要

Re-evaluation of B and

δ

11

_{B budgets in the ocean based on mud volcanoes on land}

and offshore

C.F.YOU1,E.V.SOKOL2,Y.P.LIN3 AND C.H.CHUNG4

1 _{Department of Earth Sciences, National Cheng Kung University, email: [email protected]} 2 _{V.S. Sobolev Institute of Geology and Mineralogy, email:sokol [email protected]}

3 _{Department of Earth Sciences, National Cheng Kung University, email: [email protected]} 4. _{Department of Earth Sciences, National Cheng Kung University, email: [email protected]}

The mass imbalance of Boron (B) and B isotopes (δ11_{B) in the ocean is an outstanding geochemical}

question. The B fluxes into the ocean is much less than the outputs, possibly due to neglected remobilization flux of sedimentary B in convergent margins. Mud volcanism is common in accretion and collisional settings and is an efficient conduit from deep reservoirs to exchange. Recently, enhanced B in mud volcano fluids/sediments in Taiwan Accretionary Prism and Caucasus Continental Collision Zone. The former system shows >10 mM B in MVs and >11 mM in submarine MVs, where the latter system displays up to >148 mM B in MVs, 510~1600 ppm B in mud and illite-rich clays. These B-bearing minerals may shed lights on the missing B sources. At the Kerch peninsula, unique accumulation of hydrated Na and Na-Ca borates. The ambient environments of NaCl-dominated MVs are optimal for ulexite crystallization. Separated ulexite, tincalconite, borax and B-enriched clays will be analyzed and to combine with other stable isotopes results in MVs for a detailed examination of the B sources and fractionation.

5

四、建議

無。

五、攜回資料名稱及內容

劉博士因參加 Reactive transport model 的工作坊，攜回研討會課程講義乙份、

Geochemist’ WorkBench V14 案例研究操作指南乙份、及 Geochemist’ WorkBench 案例研究模 型 source code 乙批。

六、其他

108年度專題研究計畫成果彙整表

計畫主持人：游鎮烽 計畫編號： 108-2116-M-006-011-計畫名稱：利用非傳統穩定同位素探討前寒武紀/寒武紀過渡期之古環境變化(III) 成果項目 量化 單位 質化 （說明：各成果項目請附佐證資料或細 項說明，如期刊名稱、年份、卷期、起 訖頁數、證號...等） 　　　　　　　 國 內 學術性論文 期刊論文 0 篇 研討會論文 0 專書 0 本 專書論文 0 章 技術報告 0 篇 其他 0 篇 國 外 學術性論文 期刊論文 3 篇

Chung et al., (2019) (in press, Precambrian Research)

Liu et al. (2019) (in press Precambrian Research)

Wang et al. (2020) Microchemical Journal 152, 104424 , 研討會論文 0 專書 0 本 專書論文 0 章 技術報告 0 篇 其他 0 篇 參 與 計 畫 人 力 本國籍 大專生 0 人次 碩士生 5 陳宜琪、陳瑋晨、陳柏達、許哲維、洪 清宏 博士生 1 林彥伯 博士級研究人員 1 鍾全雄 專任人員 1 程安琪 非本國籍 大專生 0 碩士生 0 博士生 0 博士級研究人員 0 專任人員 0 其他成果 （無法以量化表達之成果如辦理學術活動 、獲得獎項、重要國際合作、研究成果國 際影響力及其他協助產業技術發展之具體 效益事項等，請以文字敘述填列。）