An X-ray diffraction Approach : Bulk mineral assemblages as provenance indicator of sediments from the Arctic Ocean
An X-ray diffraction Approach : Bulk mineral assemblages as provenance indicator of sediments from the Arctic Ocean
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2016-06
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通讯作者：
H. Zou
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作者：
H. Zou
古气候研究和气候模型表明，北极对气候变化非常敏感，在驱动和放大全球气候变率和海平面变化方面也发挥着关键作用。北冰洋晚第四纪古海洋学研究对认识冰期-间冰期气候变化具有重要意义。由于北冰洋中部沉积物主要由冰山和海冰搬运，物源研究可用于推断冰盖历史和表层环流模式。块状矿物组合是识别北极沉积物源区的代用指标之一。本文的主要目的是详细研究用于获得块体矿物组合结果的定量X射线衍射（qXRD）软件包RockJock，并对两个qXRD软件包RockJock和QUAX进行比较。第四章采用三组不同的人工混合物对RockJock的精度进行了评估，并提出了可能的误差来源。RockJock和QUAX的比较是基于从西伯利亚陆架海以及北冰洋中部取回的表层沉积物样品。石英、长石、方解石、白云石以及粘土矿物的总和具有较好的相关性，而单个粘土矿物的差异较大。第五章利用RockJock软件对第四章中所用的表层沉积物样品进行分析，以检验用块状矿物组合作为物源指示的可能性。结果表明，石英、Qz/Fsp、白云岩和高岭石的组合可作为物源区的判别指标。从加拿大北极地区输入的沉积物一般具有高白云石和Qz/Fsp值的特点。从欧亚北极陆架海的沉积物输入的特点一般是低白云石，Qz/Fsp，高岭石值和高石英值。虽然角闪石的含量大多太少而无法定量，但角闪石的出现可能是西伯利亚陆架海沉积物的一个指示。在第六章中，本文选取了横跨门捷列夫海岭的三个沉积物柱样，对北极中部的陆源沉积物进行了物源研究，以探讨北极中部冰盖的历史。这表明门捷列夫海岭马卡罗夫海盆一侧沉积物的物源不同于门捷列夫海岭加拿大海盆一侧沉积物的物源。MIS 16、12、10、8的IRD事件具有高白云岩含量、高石英/长石比值和低斜长石含量的特征，可能表明IRD输入来自加拿大群岛。MIS 6期的IRD事件具有石英含量高、白云岩含量低的特征，表明IRD来自欧亚大陆。
Paleoclimate research and climate models demonstrate that the Arctic is very sensitive to climate change and also plays a key role in driving and amplifying global climate variability and sea-level change. Study of the late Quaternary paleoceanography in the Arctic Ocean is of great importance to understand the glacial-interglacial climate changes. As the sediment in the central Arctic Ocean is mostly transported by iceberg and sea-ice, provenance studies can be used to infer the ice-sheet history and the surface circulation pattern. Bulk mineral assemblages are one of the proxies that can be used to identify the source areas of the Arctic sediments. The main aim of this thesis is to study in detail the quantitative X-Ray Diffraction (qXRD) software package RockJock which is used to obtain the bulk mineral assemblages result and the comparison of the two qXRD software packages RockJock and QUAX. In Chapter 4, three different sets of artificial mixtures are used to access the accuracy of RockJock, and the possible sources of errors are proposed. The comparison of RockJock and QUAX is based on the surface sediment samples retrieved from the Siberian shelf seas as well as the central Arctic Ocean. Quartz, feldspars, calcite, dolomite, and the sum of clay minerals show fairly good correlations, while the differences of individual clay minerals are high. In Chapter 5, surface sediment samples, which are used in Chapter 4, were analyzed using RockJock to test the possibility to use bulk mineral assemblages as provenance indicator. It shows that the combination of quartz, Qz/Fsp, dolomite and kaolinite can be used to identify source areas. Sediment input from the Canadian Arctic is generally characterized by high dolomite and Qz/Fsp values. Sediment input from the Eurasian Arctic shelf seas is generally characterized by low dolomite, Qz/Fsp, kaolinite values and high quartz values. Although the contents of amphibole are mostly too small to be quantified, the occurrence of amphibole might be an indicator of sediments from the Siberian shelf seas. In Chapter 6, three sediment cores selected from a transect across the Mendeleev Ridge were used in this thesis to study the provenance of terrigenous sediments from the Central Arctic in order to study the ice sheet history. It shows that the provenance of sediments deposited on the Makarov Basin side of the Mendeleev Ridge is different from that deposited on the Canada Basin side of the Mendeleev Ridge. The IRD events of MIS16, 12, 10, 8 are characterized by high dolomite contents, high quartz/feldspar ratios and low plagioclase contents and may suggest IRD input from the Canadian Archipelago. The IRD events that occur in MIS6, are characterized by high quartz and low dolomite contents, which indicates IRD from the Eurasian sources.