Archean Oil: Evidence for Extensive Hydrocarbon Generation and Migration 2.5-3.5 Ga
Archean Oil: Evidence for Extensive Hydrocarbon Generation and Migration 2.5-3.5 Ga
复制标题
太古代石油：大量碳氢化合物生成和运移的证据 2.5-3.5 Ga
DOI：
--
复制
发表时间：
1998
期刊：
影响因子：
--
通讯作者：
B. Krapež
中科院分区：
文献类型：
--
作者：
R. Buick;B. Rasmussen;B. Krapež
来自澳大利亚皮尔巴拉盆地的太古代沉积岩中含有石油生成和运移的证据，这些证据以沥青结核的形式存在，沥青结核是由碎屑晶质铀矿、钍石和独居石颗粒周围的流体烃的放射性固定作用产生的。这些结核保存在Fortescue群（~2.75 Ga）和Lalla Rookh组（~3.0 Ga）（均为非海相序列）的多个地层水平的砂岩中，以及Mosquito Creek组（~3.25 Ga）的三角洲沉积物中。最古老的证据来自Warrawoona群（>3.46 Ga），烃滴显然是在早期热液硅化作用期间通过快速成熟从干酪根沉积物原位形成的。石油沥青遗迹也通常保存在南非Kaapvaal盆地黑礁组（~2.59 Ga）和威特沃特斯兰德超群（~2.85 Ga）的浅海砂岩中，沿着有次经济甲烷聚集。在所有情况下，石油显然是来自太古代页岩，在太古代期间产生的，并在太古代晚期或早元古代早期变质作用封闭流体通道之前迁移。鉴于太古代沉积盆地中烃类生成和迁移的广泛而丰富的证据，似乎原始细菌生物质，产生不稳定的I型干酪根，通常被埋在足够的数量，以成功地生成和排出石油。古代盆地上的沉积盆地显然含有渗透性岩石，这些岩石适合石油的迁移，也可能适合石油的聚集。因此，阻碍在太古代盆地中发现经济上可开采的油气藏的主要因素是变形和变质作用的后续破坏作用，其导致圈闭破裂、不完全封闭或热闭塞。然而，在一些古老的稳定岩块中，这种破坏可能没有发生，因此石油勘探者可能希望重新评估在太古代岩石中发现有价值的碳氢化合物资源的可能性。
Archean sedimentary rocks from the Pilbara Craton, Australia, contain evidence for petroleum generation and migration in the form of bitumen nodules produced by radiogenic immobilization of fluid hydrocarbons around detrital uraninite, thorite, and monazite grains. The nodules are preserved in sandstones at several stratigraphic levels in the Fortescue Group (~2.75 Ga) and Lalla Rookh Formation (~3.0 Ga), both nonmarine successions, and in deltaic sediments of the Mosquito Creek Formation (~3.25 Ga). The most ancient evidence comes from the Warrawoona Group (>3.46 Ga), where hydrocarbon droplets were apparently formed in situ from kerogenous sediments by flash maturation during early hydrothermal silicification. Bituminous relics of petroleum are also commonly preserved in shallow-marine sandstones of the Black Reef Formation (~2.59 Ga) and the Witwatersrand Supergroup (~2.85 Ga) from the Kaapvaal Craton, South Africa, along with subeconomic methane accumulations. In all cases, the petroleum was apparently sourced from Archean shales, generated during the Archean, and migrated before the late Archean or early Early Proterozoic metamorphism occluded fluid pathways. Given this widespread and abundant evidence for hydrocarbon generation and migration in Archean depositional basins, it seems that primordial bacterial biomass, producing labile type I kerogen, was often buried in sufficient quantities to successfully generate and expel petroleum. Depositional basins on ancient cratons clearly contained permeable rocks amenable to the migration, and probably to the accumulation, of petroleum. Thus, the main factors precluding the discovery of economically exploitable hydrocarbon accumulations in Archean basins are the subsequent destructive effects of deformation and metamorphism, which causes trap breaching, imperfect sealing, or thermal obliteration. However, there are ancient stable cratons where such disruption may not have occurred, and so petroleum explorers may wish to reassess the possibility of finding valuable hydrocarbon resources in Archean rocks.