6. CHEMISTRY AND ORIGIN OF SECONDARY MINERALS FROM THE DEEP SHEETED DIKES CORED DURING LEG 148 (HOLE 504B)1
6. CHEMISTRY AND ORIGIN OF SECONDARY MINERALS FROM THE DEEP SHEETED DIKES CORED DURING LEG 148 (HOLE 504B)1
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6. 148 段（504B 孔）1 期间深层板岩岩脉中次生矿物的化学成分和来源
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
J. Alt
中科院分区：
文献类型：
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作者：
D. Vanko;C. Laverne;P. Tartarotti;J. Alt
在第148航次取芯的下部席状岩脉中，蚀变闪长岩的次生矿物学包括早期的高温组合，包括角闪石、透辉石、钙长石斜长石、方解石、钛铁矿和磷灰石，随后在较低温度下的蚀变叠加，导致阳起石、钠长石、钠长石或绿泥石-蒙皂石、滑石、绿帘石和含水钙硅酸盐（现在的浊沸石）。次生矿物作为原始火成岩矿物的普遍替代物出现;然而，它们在不规则斑块、热液脉的厘米级晕和毫米级脉中最丰富。第148航段下部席状岩脉最初可能在轴向热液系统的“反应区”内发生了蚀变。次生斜长石的成分从钙长石到钠长石不等：都是贫钾（400°C）的大洋中脊反应区的特征。后期的阳起石+钠长石+钠长石和绿帘石+石英很可能是在轴向热液活动减弱的较低温度下形成的。钙斜长石的高温蚀变组合的存在挑战了广泛持有的概念，根据oftsample蚀变玄武岩，辉绿岩，细碧岩，大洋中脊反应带的主要斜长石是钠长石。来自504 B孔的证据以及最近的实验研究表明，钠长石是反应带中较晚的斜长石，它是在热液条件减弱时形成的。
The secondary mineralogy of altered diabase in the lower sheeted dikes cored during Leg 148 comprises an earlier hightemperature assemblage of amphibole, diopside, anorthitic plagioclase, chlorite, titanite, and apatite, overprinted by a subsequent alteration at lower temperatures that led to actinolite, albite, chlorite or chlorite-smectite, talc, epidote, and hydrous calcsilicate (now laumontite). Secondary minerals occur as a pervasive replacement of original igneous minerals; however, they are modally most abundant within irregular patches, centimeter-scale halos of hydrothermal veins, and millimeter-scale veins. The lower sheeted dikes of Leg 148 may have been altered initially within the "reaction zone" of an axial hydrothermal system. Secondary plagioclase compositions range from anorthite to albite: all are K2O poor ( 400°C) characteristic of the mid-ocean-ridge reaction zone. Later generations of actinolite + chlorite + albite and epidote + quartz most likely formed at lower temperatures during the waning of axial hydrothermal activity. The presence of calcic plagioclase in the high-temperature alteration assemblage challenges the widely held notion, based upon oftsampled altered basalts, diabases, and spilites, that the dominant plagioclase of the mid-ocean-ridge reaction zone is albite. Evidence from Hole 504B, as well as recent experimental studies, suggests that albite is a later plagioclase in the reaction zone, which formed during waning hydrothermal conditions.