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首页> 外文期刊>Sedimentology: Journal of the International Association of Sedimentologists >Origin of blocky aragonite cement in Cenozoic glaciomarine sediments, McMurdo Sound, Antarctica
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Origin of blocky aragonite cement in Cenozoic glaciomarine sediments, McMurdo Sound, Antarctica

机译：在新生代甘草胺沉积物中，块状神经水泥的起源，南极洲McMurdo声音

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摘要

Inorganic aragonite occurs in a wide spectrum of depositional environments and its precipitation is controlled by complex physio-chemical factors. This study investigates diagenetic conditions that led to aragonite cement precipitation in Cenozoic glaciomarine deposits of McMurdo Sound, Antarctica. A total of 42 sandstones that host intergranular cement were collected from the CIROS-1 core, located proximal to the terminus of Ferrar Glacier. Standard petrography, Raman spectroscopy and electron microprobe analysis reveal a prominent aragonite cement phase that occurs as a pore-filling blocky fabric throughout the core. Oxygen isotope compositions (delta O-18 = -30 center dot 0 to -8 center dot 6 parts per thousand Vienna Pee-Dee Belemnite) and clumped isotope temperatures (T Delta(47) = 13 center dot 1 to 31 center dot 5 degrees C) determined from the aragonite cements provide precise constraints on isotopic compositions (delta O-18(w)) of the parent fluid, which mostly range from -10 center dot 8 to -7 center dot 2 parts per thousand Vienna Standard Mean Ocean Water. The fluid delta O-18(w) values are consistent with those of pore water, previously identified as cryogenic brine in the nearby AND-2A core. Petrographic and geochemical data suggest that aragonite cement in the CIROS-1 core precipitated from a similar brine. The brine likely formed and infiltrated sediments in flooded glacial valleys along the western margin of McMurdo Sound during the middle Miocene Climatic Transition, and subsequently flowed basinward in the subsurface. Consequently, the brine forms as a longstanding subsurface fluid that has saturated Cenozoic sediments below southern McMurdo Sound since at least the middle Miocene. Aragonite cementation in the CIROS-1 core is interpreted to reflect its proximal position to sites of brine formation and greater likelihood of experiencing brines with sustained high carbonate saturation states and Mg/Ca ratios. This unusual occurrence expands the range of known natural occurrences of aragonite cement. Given the potential for cryogenic brine formation in glaciomarine settings, blocky aragonite, as the end member of the spectrum of aragonite cement morphology, may be more widespread in glaciomarine sediments than currently thought.
机译：无机杂散发生在宽的沉积环境中，其沉淀由复杂的物理化学因素控制。本研究研究了在南极洲McMurdo Sound的新生代甘油胺沉积物中导致的成岩石病症。共收集宿主晶体水泥的42个砂岩，从Ciros-1核心收集，位于近端到铁云冰川末端。标准透视，拉曼光谱和电子微探针分析显示出突出的化石水泥相，其在整个芯中作为孔填充块状织物发生。氧同位素组合物（Delta O-18 = -30中心点0至-8中心点6份每千维也纳撒尿Banemnite）和丛生同位素温度（TΔ（47）= 13中心点1至31中心点5度C）由化甲酸酯确定的C）对本体液的同位素组合物（Delta O-18（W））提供了精确的限制，其主要是-10中心点8至-7中心点2份每千维也纳标准的平均海水。流体δO-18（W）值与孔隙水的值一致，先前鉴定为附近的和2A芯中的低温盐水。岩体和地球化学数据表明，来自类似盐水沉淀的CIROS-1核中的金属石水泥。盐水可能在中间内科气候过渡期间沿着McMurdo声音的西部覆盖而形成和渗透淹没的冰川山脉，随后在地下流动。因此，盐水形式作为长期的地下流体，其在南部McMurdo声音下具有饱和的新生代沉积物，因为至少是中间内烯。 CiROS-1核心的化石胶质被解释为将其对盐水形成部位的近端位置和更大的可能性，以持续的高碳饱和状态和MG / CA比率进行盐水。这种不寻常的发生扩展了已知的神圣水泥的自然出现范围。鉴于冰川甘油氨基测定中的低温盐水形成的可能性，块状的金属石作为化石水泥形态的光谱的最终成员，可能比目前思维更广泛。

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