Noble gas and halogen constraints on regionally extensive mid-crustal Na-Ca metasomatism, the Proterozoic Eastern Mount Isa Block, Australia
Noble gas and halogen constraints on regionally extensive mid-crustal Na-Ca metasomatism, the Proterozoic Eastern Mount Isa Block, Australia
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DOI：
10.1016/j.precamres.2007.08.015
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发表时间：
2008-05-20
影响因子：
3.8
通讯作者：
Williams, P. J.
中科院分区：
文献类型：
--
作者：
Kendrick, M. A.;Baker, T.;Williams, P. J.
本文分析了东伊萨地块玛丽凯瑟琳褶皱带和克隆库里区与区域钠钙蚀变（钠长石化）有关的伊萨晚期石英脉中的流体包裹体的天然和中子产生的Ar、Kr和Ar同位素。稀有气体的提取使用热爆裂过程，使部分反褶积的不同类型的流体包裹体，包括微咸水，液态二氧化碳和混合的水-碳品种。微咸水（< 5-65重量%）的水流体包裹体占主导地位，并具有在大多数样品的At-40/Ar-36值小于2700从整个地区。这些流体包裹体的Br/Cl摩尔值变化很大，为0.3-4 × 10 ~（-3），I/Cl摩尔值变化很大，为0.2-35 × 10 ~（-6克隆库里地区蛇溪背斜样品中的流体包裹体具有最高的Ar-40/Ar-40比值，36的值类似于25，000，表明在这种情况下，深部岩浆或变质流体起源。岩浆起源是有利的，因为这种流体非常类似于欧内斯特亨利的氧化铁铜金（IOCG）成矿作用中涉及的流体，后者也被解释为具有岩浆起源，由于其Br/Cl值接近于1-2 × 10 ~（-3），I/Cl值接近于-10 × 10 ~（-6），与幔源岩浆岩的特征相似，因此其碳-在玛丽凯瑟琳褶皱带的诺比采石场样品中，二氧化硅流体包裹体占主导地位，Ar-40/Ar-36最大值为6000-7000。这些流体包裹体的Ar-36浓度估计为1-4 ppb，这与所有其他样品中含水流体包裹体的浓度范围相似。此外，所有样品中的水、碳流体包裹体的δ ~（129）/Ar ~（36）+Kr ~（84）/Ar ~（36）值均为未分馏值，接近于空气-空气饱和水（ASW）范围，表明CO2具有独立的变质成因，混合型水-碳流体包裹体的存在是由于流体混合或混合作用的结果。而不是流体不混合。然而，这些数据并不排除存在一个小的岩浆CO2成分的样品从Knobby Quarry.Fluid包裹体中的大多数样品从玛丽凯瑟琳褶皱带具有较高的Br/Cl和I/Cl值，较高的Ar-36浓度和较低的最大Ar-40/Ar-36值比流体包裹体样品从克隆库里区。这表明东伊萨地块不同部位的钠钙蚀变是独立发生的。然而，与钠钙蚀变在克隆库里区的流体包裹体有一个非常相似的组成IOCG矿化阶段的石英脉Ernest亨利.这些数据因此是兼容的区域钠钙蚀变和IOCG矿化之间的成因关系在克隆库里区的流体包裹体。在这两种情况下，超盐水热液流体的主要来源于沉积地层水，但被解释为含有岩浆成分来源于后期伊桑威廉姆斯奈落岩，这可能是驱动流体对流。(c)2007 Elsevier B.V保留所有权利。
Fluid inclusions in late-Isan quartz veins associated with regional Na-Ca alteration (albitisation), in the Mary Kathleen Fold Belt and the Cloncurry District of the Eastern Mt Isa Block, have been analysed for naturally occurring and neutron produced isotopes of Ar, Kr and Xe. The noble gases have been extracted using a thermal decrepitation procedure that enables partial deconvolution of the different fluid inclusion types, including variably saline aqueous, liquid carbon-dioxide and mixed aqueous-carbonic varieties.The variably saline (< 5-65 wt%) aqueous fluid inclusions dominate and have At-40/Ar-36 values of less than 2700 in most of the samples from across the region. These fluid inclusions have extremely variable molar Br/Cl values of 0.3-4 x 10(-3) and I/Cl values of 0.2-35 x 10(-6) and the fluids are interpreted to represent sedimentary formation waters derived from the upper crust that have dissolved variable quantities of halite (or scapolite) to achieve their ultra-high salinity.Fluid inclusions in a sample from the Snake Creek anticline in the Cloncurry District have the highest Ar-40/Ar-36 value of similar to 25,000 demonstrating a deep magmatic or metamorphic fluid origin in this case. A magmatic origin is favoured because this fluid is very similar to a fluid involved in Iron-Oxide-Copper-Gold (IOCG) mineralization at Ernest Henry that was also interpreted to have a magmatic origin, and because the aqueous fluid inclusions have Br/Cl of similar to 1-2 x 10(-3) and I/Cl of similar to-10 x 10(-6) that are similar to mantle-derived igneous rocks.Carbon-dioxide fluid inclusions dominate samples from the Knobby Quarry in the Mary Kathleen Fold Belt and have a maximum Ar-40/Ar-36 value of 6000-7000. These fluid inclusions are estimated to have a Ar-36 concentration of 1-4 ppb, that is similar to the range determined for aqueous fluid inclusions in all the other samples. In addition, aqueous and carbonic fluid inclusions in all the samples have similar Xe-129/Ar-36 plus Kr-84/Ar-36 values that are unfractionated, and close to the air-Air Saturated Water (ASW) range.These data are interpreted to indicate an independent and dominantly metamorphic origin for CO2, and the presence of mixed aqueous-carbonic fluid inclusions are attributed to fluid mixing and/or mingling, rather than fluid unmixing. However, the data do not preclude the presence of a minor magmatic CO2 component in the samples from the Knobby Quarry.Fluid inclusions in most of the samples from the Mary Kathleen Fold Belt have higher Br/Cl and I/Cl values, higher Ar-36 concentrations and lower maximum Ar-40/Ar-36 values than fluid inclusions in samples from the Cloncurry District. This suggests Na-Ca alteration in these different parts of the Eastern Mt Isa Block occurred independently. However, fluid inclusions associated with Na-Ca alteration in the Cloncurry District have a very similar composition to fluid inclusions in IOCG mineralization-stage quartz veins from Ernest Henry.These data are therefore compatible with a genetic relationship between regional Na-Ca alteration and IOCG mineralization in the Cloncurry District. In both cases the ultra-saline hydrothermal fluids had a dominant origin from sedimentary formation water, but are interpreted to contain a magmatic component sourced from the late-Isan Williams-Naraku Batholiths which may have driven fluid convection. (c) 2007 Elsevier B.V All rights reserved.