Superconducting single crystals
Superconducting single crystals
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超导单晶
作者：
I. Tanaka;H. Kojima
SIR-Bird和Chivas的工作基于三个假设：（1）被认为是形成深度风化剖面的物质是在过去某个时间在热带条件下的低起伏地形上形成的;（2）这种强烈风化期的日期可以通过足够精确的方法来确定，以校准其氧同位素结果;（3）用于氧同位素分析的粘土矿物是在强烈风化过程中形成的。我们在两个地点调查了第一个假设。第一个地点是悉尼附近霍克斯伯里砂岩上的红土和深度风化剖面。这些物质通常被认为是在中新世和/或上新世在强烈的热带风化作用下在低起伏表面上形成的化石土壤的侵蚀残留物3。我们的矿物学、地球化学和古地磁调查4 -6表明，这些红土和相关的深风化剖面是在Wianamatta页岩的不透水覆盖层逐渐剥离期间形成的，为铁的活化提供了必要的环境条件。换句话说，所有的红土都是由Wianamatta页岩从Hawkesbury砂岩中剥离的速率控制的时间海侵过程的结果，而深层风化剖面可以用正常的基岩变化来解释。我们的第二个地点位于新南威尔士州中西部的Cobar地区，其中硅质岩和相关的深风化剖面被认为是在第三纪的山麓上发育的。对这些材料的详细矿物学和地球化学调查”统计“表明，这些遗址的石英质古生代基岩自晚古生代变形以来基本上保持不变，硅质岩和深层硅质岩都是由石英质岩石构成的。
SIR-The work reported1 by Bird and Chivas is based on three assumptions:(1) that materials recognized as forming deeply weathered profiles have been formed at some time in the past, on landscapes of low relief under tropical conditions;(2) that the date of such intense periods of weathering can be established by a method of sufficient accuracy to calibrate their oxygen isotope results; and (3) that the clay minerals used for oxygenisotope analysis were formed during the intense weathering process. We investigated the first assumption at two sites. The first site was the laterites and deeply weathered profiles on the Hawkesbury Sandstone near Sydney. These materials are generally regarded as erosional remnants of a fossil soil, formed in the Miocene and/or Pliocene, under intense tropical weathering, on a surface of low relief'· 3• Our mineralogical, geochemical and palaeomagnetic investigations4-6 demonstrate that these laterites and associated deep-weathered profiles were formed during the gradual stripping of the impervious cover of the Wianamatta shales, which provided the necessary environmental conditions for the mobilization of iron. In other words, all the laterites are the result of a timetransgressive process controlled by the rate at which the Wianamatta shale is being stripped from the Hawkesbury Sandstone, whereas the deep-weathering profiles are explicable in terms of normal bedrock variability.Our second site was in the Cobar region of central western New South Wales, where silcretes and associated deepweathered profiles had been recognizedH as having developed on a Tertiary pediplain. Detailed mineralogical and geochemical investigations of these materials"·'show that the quartzitic Palaeozoic bedrock of these sites has remained essentially unaltered since a late Palaeozoic deformation and that both silcretes and deep-