Banded Iron-Formations through Much of Precambrian Time
Banded Iron-Formations through Much of Precambrian Time
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前寒武纪大部分时期的带状铁地层
DOI：
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发表时间：
1981
期刊：
影响因子：
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通讯作者：
C. Klein
中科院分区：
文献类型：
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作者：
M. Gole;C. Klein
元古代（~ 1.8-2.5 Gyr）和太古代（> 2.5 Gyr）条带状铁建造之间的相似性可能比它们的差异更重要。这种对比在很大程度上反映了元古代和太古代地体构造环境的差异。太古代带状含铁地层不像元古代主要含铁地层那样厚，横向上也不像元古代主要含铁地层那样广泛。尽管如此，一些太古代铁地层的走向长度超过150-200公里，并且在影响大多数太古代地形的变形之前可能已经相当广泛。含铁建造的地层序列变化很大，表明含铁建造形成于多种沉积环境。铁地层中的沉积结构主要是颗粒和软陶或纹层（包括微带），反映了它们沉积的物理条件的差异。仅在三个元古代沉积盆地中有丰富的粒状和鲕状结构，并且大多数前寒武纪铁建造都是层状的。尽管在相关的岩性和沉积结构的差异前寒武纪铁形成有相似的整体组成和矿物组合，这意味着铁形成沉积的化学条件是相似的，通过前寒武纪的大部分。带状铁建造的形成似乎没有达到最大值约1.8-2.0 Gyr，但已在前寒武纪的一个重要的过程，在很长一段时间。
Similarities between Proterozoic (~ 1.8-2.5 Gyr) and Archean (> 2.5 Gyr) banded iron-formations are probably more significant than their differences. The contrasts largely reflect differences in the tectonic settings of Proterozoic and Archean terrains. Archean banded iron-formations are not as thick nor laterally as extensive as the major Proterozoic iron-formations. Nevertheless, some Archean iron-formations have strike lengths of over 150-200 km and may have been quite extensive prior to the deformation that has affected most Archean terrains. Stratigraphic sequences in which iron-formations occur are highly variable and indicate that iron-formations formed in many depositional environments. Sedimentary textures in the iron-formations are dominated either by granules and oolites or laminations (including microbanding) reflecting differences in their physical conditions of deposition. Granular and oolitic textures are abundant in only three Proterozoic depositional basins and most Precambrian iron-formations are laminated. Despite differences in associated lithologies and sedimentary textures Precambrian iron-formations have similar bulk compositions and mineral assemblages, implying that the chemical conditions of iron-formation deposition were similar through much of the Precambrian. The formation of banded iron-formation appears not to have reached a maximum around 1.8-2.0 Gyr but to have been an important process over a long period in the Precambrian.