Micritized Skeletal Grains in Northern Belize Lagoon: A Major Source of Mg-calcite Mud
Micritized Skeletal Grains in Northern Belize Lagoon: A Major Source of Mg-calcite Mud
复制标题
伯利兹北部泻湖的微晶化骨骼颗粒：镁方解石泥的主要来源
DOI：
10.1306/d42678b1-2b26-11d7-8648000102c1865d
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发表时间：
1992
影响因子：
2
通讯作者：
J. Post
中科院分区：
文献类型：
--
作者：
R. Reid;I. Macintyre;J. Post
摘要伯利兹泻湖北方的石灰泥主要由粉砂级隐晶质颗粒和粘土级团块组成，两者均由尺寸小于0.5 µm的等轴晶体组成。该泥浆是含有9-10摩尔% MgCO 3的70-90%镁方解石。详细的岩相学、形态学和矿物学分析表明，隐晶质颗粒是微晶化的骨骼颗粒，这些蚀变颗粒的磨损和生物侵蚀形成了泥浆。微晶化的骨骼颗粒发生主要是由原来的骨骼碳酸盐（板条，棱镜和叶片的镁方解石，文石和方解石）重结晶等晶的微晶镁方解石，与额外的蚀变微晶充填的microborings和骨骼腔。由于原始骨架组分与其微晶化对应物的晶体形态和矿物学之间的差异，由微晶化颗粒减少产生的泥浆不同于由骨架分解产生的泥浆。巴哈马群岛和其他浅碳酸盐环境中大量的隐晶质颗粒表明，泥晶化颗粒可能是以前未被确定的石灰泥的重要来源。
ABSTRACT Lime mud in northern Belize lagoon is composed predominantly of silt-size cryptocrystalline grains and clay-size clumps, both of which consist of anhedral, equant crystals less than 0.5 µm in size. This mud is 70-90% Mg-calcite containing 9-10 mole % MgCO3. Detailed petrographic, morphologic and mineralogic analyses suggest that the cryptocrystalline grains are micritized skeletal grains and that the mud formed by abrasion and bioerosion of these altered grains. Micritization of skeletal grains occurred primarily by recrystallization of original skeletal carbonate (laths, prisms and blades of Mg-calcite, aragonite and calcite) to equant crystals of micritic Mg-calcite, with additional alteration by micritic infilling of microborings and skeletal cavities. Because of d fferences between crystal morphologies and mineralogies of original skeletal components and their micritized counterparts, mud produced by diminution of micritized grains is distinct from that produced by skeletal breakdown. The abundance of cryptocrystalline grains in the Bahamas and other shallow carbonate environments suggests that micritized grains are potentially an important source of lime mud that has not previously been identified.