Fluid migration and vein formation during deformation and greenschist facies metamorphism at Ormiston Gorge, central Australia
Fluid migration and vein formation during deformation and greenschist facies metamorphism at Ormiston Gorge, central Australia
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DOI：
10.1111/j.1525-1314.1994.tb00030.x
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发表时间：
1994-07
影响因子：
3.4
通讯作者：
I. Cartwright;W. Power;N. Oliver;R. Valenta;G. S. Mclatchie
中科院分区：
文献类型：
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作者：
I. Cartwright;W. Power;N. Oliver;R. Valenta;G. S. Mclatchie
在艾丽斯·斯普林斯造山运动期间，澳大利亚中部奥米斯顿峡谷的变形发生在下到中绿片岩相条件下。苦泉组的白云岩和石英岩。堆积石英岩中的变质岩芯和变质岩中含有丰富的早期、同生和后构造脉体。然而，尽管局部矿脉密度接近15%，但矿脉的分布以及围岩和矿脉的氧同位素地球化学表明，流体活动是局部规模的。石英脉的δ18O值(13.5-16.9‰)与围岩(13.6-16.9‰)相似，Δ18O(脉-围岩)值为-0.6-0.4‰。相比之下，苦泉组以白云岩为主，δ-18O值为23.4-27.7‰。即使在Heavitree和苦泉岩之间的边界也观察到了这些差异，这意味着这些岩石之间没有发生重大的流体交换。或者，流体流动是通过本研究样本以外的区域进行的。与粗树石英岩相比，苦泉组单个围岩的δ18O值(23.3-29.1‰)明显高于脉岩，δ18O(脉-围岩)值高达-4‰(平均为-2.1‰)。这些δ18O值的系统差异很可能是流体不混溶或不平衡溶解引起的氧同位素分馏造成的。部分白云岩脉体与围岩的δ~(13)C值差异较小[δ~(13)C(脉体-围岩)高达-1.9‰，平均为-0.5‰]。这项研究表明，特定岩石单元内的反复压裂和流体运移可能会产生大量的矿脉，而不涉及大量的外部派生流体。
During the Alice Springs Orogeny, deformation at Ormiston Gorge, central Australia, occurred under lower- to middle-greenschist facies conditions. Dolomites of the Bitter Springs Formation and quartzites. metagreywackes, and metapelites of the Heavitree Quartzite contain abundant early-, syn-, and post-tectonic veins. However, though vein densities locally approach 15%, the distribution of veins and the oxygen isotope geochemistry of wallrocks and veins suggest that fluid movement was on a local scale. The Heavitree Quartzite contains quartz veins that, even along the main thrust plane, have similar δ18O values (13.5–16.9%o) to those of their wallrocks (13.6–16.9%o), with Δ18O(vein-wallrock) values of -0.6 to 0.4%o. In contrast, the Bitter Springs Formation contains predominantly dolomite veins that have δ18O values of 23.4 to 27.7%o. These differences are observed even at the boundary between the Heavitree and Bitter Springs rocks, implying that significant fluid exchange between these rocks has not occurred, or that fluid flow was channelled through areas outside those sampled for this study. By contrast with the Heavitree Quartzite, δ18O values of wallrocks in individual samples of the Bitter Springs Formation are significantly higher (23.3–29.1%o) than those of the veins, with δ18O(vein-wallrock) values up to -4%o (average of -2.1%o). These systematic differences in δ18O values most likely result from oxygen isotope fractionation caused by fluid immiscibility or disequilibrium dissolution. Smaller differences in δ13C values between some dolomite veins and wallrocks [δ13C(vein-wallrock) up to -1.9%o, average of -0.5%o] are also explained by these processes. This study indicates that large volumes of veins may be produced by repeated fracturing and fluid migration within particular rock units, without involving large volumes of externally derived fluids.