Provenance of glacial–marine sediments under the McMurdo/Ross Ice Shelf (Windless Bight, Antarctica): Heavy minerals and geochemical data
Provenance of glacial–marine sediments under the McMurdo/Ross Ice Shelf (Windless Bight, Antarctica): Heavy minerals and geochemical data
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麦克默多/罗斯冰架（南极洲无风湾）下冰川-海洋沉积物的来源：重矿物和地球化学数据
DOI：
10.1016/j.palaeo.2007.08.010
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
G. Giorgetti
中科院分区：
文献类型：
--
作者：
D. Damiani;G. Giorgetti
在罗斯岛后面900米深的凹陷中，麦克默多/罗斯冰架下的海底沉积物已经通过两个地点的进入孔进行了取芯。在1号遗址，在过去22年中沉积的31厘米的泥沙和较少的沙子，覆盖着30厘米厚的末次冰期最大时期的硅质岩。在2号站点，整个岩芯都是在过去12个月里沉积的泥浆。为了追踪晚第四纪沉积物来源的变化，对这两个地点的样品进行了极细砂粒大小、重矿物分析以及砂粒和粉砂组分的地球化学分析。通过光学和电子扫描显微镜(SEM-EDAX)分析对重矿物进行了鉴定。采用X射线荧光(XRF)光谱法测定了熔融玻璃圆盘上的常量元素和微量元素。重矿物组合中辉石(钛辉石、低钙辉石和顽辉石)、橄榄石和玻璃颗粒含量较高。角闪石(镁角闪石、阳起石和角闪石)、氧化物(钛铁矿和钛磁铁矿)和稳定矿物(绿帘石、石榴石和磷灰石)存在少量。1号岩心上部和2号岩心的重矿物组合均以橄榄石、钛辉石和玻璃为主，辉绿岩中辉石、钠辉石、低钙辉石、角闪石和稳定矿物增多。沉积物的地球化学与它们在砂子和粉砂组分中的矿物学组成有关。K和Rb趋势可能代表碱性长石和/或云母含量的变化。硅铝比的变化与硅酸盐矿物和/或石英含量的变化有关。镁、钙、钛、锶可能存在于岩性矿物中。这组分析表明，这些沉积物是当地麦克默多火山群和横贯北极山脉()烃源岩的混合体。直径是的强烈来源，表明主要冰流至少在18Ky之前和25Ky之后从西方流入罗斯海。上覆泥浆以MVG信号为主，两个采样点的沉积物来自冰盖的底部融化，冰盖将MVG产生的碎片困在罗斯湾南部。来自的少量矿物可以通过从西北方向流入大陆架下方的洋流提供。
Sea floor sediments beneath the McMurdo/Ross Ice Shelf in a 900-m-deep depression behind Ross Island have been cored through access holes at two sites. At Site 1, 31 cm of mud and lesser sand, deposited over the last 22 ka, overlies a 30-cm-thick diamictite of the Last Glacial Maximum. At Site 2, the entire core is mud deposited over the last 12 ka. Analyses of very fine sand-sized, heavy minerals and geochemical analyses of the sand and silt fractions have been carried out on samples from both sites to track variations in sediment provenance through the Late Quaternary. The heavy minerals were identified by optical and electron scanning microscope (SEM-EDAX) analysis. Major and trace elements were determined on fused glass discs by X-ray fluorescence (XRF) spectrometry. Heavy mineral assemblages have high concentrations of pyroxenes (titanoaugite, augite, pigeonite, low-Ca augite and enstatite), olivines and glass grains. Amphiboles (Mg-hornblende, actinolite and kearsutite), oxides (titanite and titanomagnetite) and stable minerals (epidote, garnet, and apatite) are present in minor amounts. Olivine, titanoaugite and glass dominate the heavy mineral assemblages both in upper part of core 1 and in all of core 2. In the diamictite, an increase of augite, pigeonite, low-Ca augite, hornblende and stable minerals are observed. The sediment geochemistry is linked to their mineralogical composition both in the sand and in the silt fractions. K and Rb trends probably represent variations in alkali feldspar and/or mica content. The variation of Si/Al ratio is due to sialic minerals and/or to quartz content variation. Mg, Ca, Ti, Sr are probably comprised in femic minerals. The sets of analyses show that the sediments are a mix of local McMurdo Volcanic Group (MVG) rocks and Transantarctic Mountains (TAM) source rocks to the south and west. The diamicton was a strong TAM provenance, suggesting that the main ice streams drained into the Ross Sea from the West at least prior to 18 ky and later than 25 ky. The overlying mud is dominated by a MVG signal, sediments in the two sampled sites derive from basal melting of the ice sheet which entrapped debris from MVG cropping out to the South of the Ross Embayment. Small quantities of minerals from the TAM can be supplied by marine currents inflowing under the shelf from NW.