Origin of quartz cements in some sandstones from the Jurassic of the Inner Moray Firth (UK)
Origin of quartz cements in some sandstones from the Jurassic of the Inner Moray Firth (UK)
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DOI：
10.1111/j.1365-3091.1994.tb01411.x
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发表时间：
1994-04
期刊：
影响因子：
3.5
通讯作者：
Grete Block Vagle;A. Hurst;H. Dypvik
中科院分区：
文献类型：
--
作者：
Grete Block Vagle;A. Hurst;H. Dypvik
牛津阶布罗拉砂质组（Oxfordian）浅海砂岩中石英胶结作用的程度与Rhaxella perforata海绵骨针的产状和丰度密切相关。三种水泥形态被确定，玉髓石英，微石英和中石英。玉髓状石英形成基质支撑的水泥，其保存了Rhaxella骨针的模具。玉髓状石英晶体具有不均匀的晶面发育，平均直径为0.1 μm，是最早形成的胶结物，在SEM-CL/BEI上显示出均匀的深灰色色调。微石英形成直径5-10 μm的晶体，通常生长在玉髓石英衬底上，在SEM-CL/BEI下显示各种灰色色调。中石英晶体与其基质颗粒呈光学连续性生长，具有>20 μm的a轴直径晶体，并表现出明显的分区发光。虽然没有蛋白石二氧化硅保存，石英水泥被解释为已形成的蛋白石前体。碎屑石英的δ 18 O平均值为+12.2 ‰，中石英（同轴增生）的δ 18 O平均值为+20 ‰。由于要将两种结构类型分开，对细石英和玉髓石英的δ 18 O组成的估计变得复杂;两者的混合物的δ 18 O组成始终高于中石英，较高的估计值为+39统计2 ‰。根据氧同位素数据，石英、微石英和玉髓石英的形成被解释为发生在35 - 71°C的海洋孔隙沃茨中。有机和无机成熟数据将温度上限限制在60°C以下。
The extent of quartz cementation in shallow marine sandstones of the Brora Arenaceous Formation (Oxfordian) is closely related to the occurrence and abundance of Rhaxella perforata sponge spicules. Three cement morphologies are identified, chalcedonic quartz, microquartz and mesoquartz. Chalcedonic quartz forms matrix-supported cements which preserve moulds of Rhaxella spicules. Chalcedonic quartz crystals have inequant development of crystal faces, on average 0·1 μm in diameter, and are the first formed cement and reveal homogeneous dark grey tones on the SEM-CL/BEI. Microquartz forms 5–10 μm diameter crystals, which commonly grow on chalcedonic quartz substrates and show various grey tones under SEM-CL/BEI. Mesoquartz crystals grow in optical continuity with their host grains, have >20 μm a-axial diameter crystals, and exhibit distinctly zoned luminescence. Although no opaline silica is preserved, the quartz cement is interpreted to have formed from an opaline precursor. Detrital quartz has an average δ18O composition of + 12·2‰ and mesoquartz (syntaxial overgrowth) has an average δ18O composition of +20·0‰. Estimates of the δ18O compositions of microquartz and chalcedonic quartz are complicated by the problem of isolating the two textural types; mixtures of the two give consistently higher δ18O compositions than mesoquartz, the higher estimate being +39·2‰. From oxygen isotope data the formation of quartz, microquartz and chalcedonic quartz is interpreted to have taken place between 35 and 71°C in marine derived pore waters. Organic and inorganic maturation data constrain the upper temperature limit to less than 60°C.