鄂霍次克海深海沈積物鐵錳相的鉬含量與鉬同位素之初步探討

• Main Authors: 戴莉, Tai Li
• Other Authors: 余英芬, 李德春, Ein-Fen Yu, De-Chun Lee
• Language: Chinese
• Published: 2019
• Subjects: 鄂霍次克海; 鐵錳萃取相; 鉬元素; 鉬同位素變動; The Okhotsk Sea; Sedimentary Fe-Mn oxyhydroxides; Molybdenum; Molybdenum isotopic composition; Okhotsk; Pacific; okhotsk sea
• Online Access: http://rportal.lib.ntnu.edu.tw:80/handle/20.500.12235/101892; https://hdl.handle.net/20.500.12235/101892; http://etds.lib.ntnu.edu.tw/cgi-bin/gs32/gsweb.cgi?o=dstdcdr&s=id=%22GN060049002S%22.&%22.id.&

近年來多接受器感應電漿質譜儀（MC-ICP-MS）迅速發展，使學術界對於原本難以解離的過渡元素—鉬元素，得以有進一步的研究和了解。前人研究中對水體中的鉬元素與同位素的研究主要包含陸地湖泊、河流、河口、開放大洋、封閉海盆；並且包含錳核、遠洋沈積物、火成岩、熱液、冰川等，但對鉬的研究以區域的涵蓋而言仍有限。鄂霍次克海為西北太平洋的邊緣海，具有陸地及開放大洋的訊號，也含有極區的特性。因此本論文工作希望透過深海沈積岩芯的分析以期探究鄂霍次克海地區的鉬及其同位素的變動。 本論文研究使用岩芯MD012414的深海沈積物標本，經萃取沈積物鐵錳相取得澄清液後，取少量進行鉬含量分析；再經層析法純化鉬元素並利用質譜儀及雙示蹤劑同位素分析技術取得鉬同位素訊號值。然後經過重複分析及不同比例添加劑的鐵錳相萃取實驗之驗證後，確認本論文工作的鉬含量及同位素值之實驗分析結果確為標本源自海洋環境系統的訊號。 經前人研究得知海洋中鉬同位素的變動可受到來源、氧化還原環境及成岩作用的影響。萃取沈積物鐵錳相可排除陸源影響，反應海水環境的訊號。研究得知在自生鐵錳氧化物吸附下的氧化鉬之鉬同位素δ98/95Mo =–0.7‰；還原環境下硫化鉬之鉬同位素為δ98/95Mo =2.3‰。另外，在已知的研究發現早期成岩作用中鉬同位素的變動範圍為δ98/95Mo =–0.7～3.5‰。而本論文工作結果顯示MD012414之鉬含量為15.7ppb～162.8ppb，鉬同位素值為–0.99～–3.12‰；此些結果與前人研究比較，都顯示本論文工作的鉬同位素值偏輕，因此認為除了反應成岩作用及氧化環境外，鄂霍次克海之鉬含量的變動與同位素分化的機制當需進一步的探討。 Recent developments in analytical technique, particularly the advantages of Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS), have allowed the precise determination of differences in the isotope compositions of Mo between samples and reference standards. Previously studies about Mo concentration and isotope composition included water samples from lake, river, estuary, open ocean and restricted basins. Other studies such as Mo concentration and isotope of manganese nodules, pelagic sediments, igneous rock, fluids of hydrothermal vent and glacials are also reported as well. However, about Mo and δ98/95Mo of a marginal sea like the Okhotsk Sea has yet been studied. The sea of Okhotsk is a marginal sea of the northwest Pacific Ocean, it accompanies with terrigenous and open ocean signals. This thesis study is hoped to add more understanding about the geochemistry of molybdenum and its isotope fractionation in the marginal sea. The experiments included a sequential leaching technique to extract the authigenic molybdenum coating on the sedimentary Fe-Mn oxyhydroxides, and a robust chromatography technique to purify molybdenum for isotope composition analyses. This procedure is different from previous studies which apply whole bulk sediment for Mo concentration and isotope analyses. In addition, ...