Paleoremanence dispersal across a transpressed Archean terrain : Deflection by anisotropy or by late compression ?
Paleoremanence dispersal across a transpressed Archean terrain : Deflection by anisotropy or by late compression ?
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古地磁在变形的太古宙地形上扩散：各向异性或后期压缩造成的偏转？
DOI：
10.1029/95jb03047
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
G. Borradaile
中科院分区：
文献类型：
--
作者：
T. Werner;G. Borradaile
奎蒂科带是一个夹在绿岩亚省之间的太古代变质沉积带。一个单一的区域磁率是近平行于磁叶理定义的各向异性的低场磁化率（AMS）和各向异性的非滞后剩磁（AARM）。定向云母是AMS的主要原因。排列的磁黄铁矿是AARM的唯一原因。每个磁性子组构是由于矿物生长在重叠的时间间隔在应变历史。它们的轻微结晶度可能是由于非共轴应变过程中的结晶。磁组构椭球表明不同程度的扁平化：非常强烈的扁平化的北方边界，南部边界不太严重，和最不严重的内部。该带的内部和南部边界呈水平伸展，缩短方向由北向NS逐渐向南向NNW变化。磁黄铁矿携带的古地磁记录显示，特征剩磁分布在一个大致平行于区域磁率和磁面理的大圆环周围。后期应力的影响旋转成这种模式的古地磁场，我们折扣偏转的各向异性。分散的模式表明，该地区的单轴扁圆扁平与NNW-SSE缩短，在变质冷却历史的后期（<300°C）。这是落后于机械性，AMS和AARM结构，但它是由相同的运动模式控制。
The Quetico Belt is an Archean metasedimentary terrain sandwiched between greenstone subprovinces. A single regional schistosity is subparallel to magnetic foliation defined by anisotropy of low-field magnetic susceptibility (AMS) and anisotropy of anhysteretic remanence (AARM). Aligned micas are the primary cause of AMS. Aligned pyrrhotite is the sole cause of AARM. Each magnetic subfabric is due to minerals that grew in overlapping intervals in the strain history. Their slight obliquity may be due to crystallization during noncoaxial strain. Magnetic fabric ellipsoids suggest varying severity of flattening: very strong flattening on the northern boundary, less severe on the southern boundary, and least severe in the interior. The interior and the southern boundary of the belt stretched horizontally and the shortening direction varies gradually, from NS in the north to NNW in the south. The paleomagnetic record carried by pyrrhotite shows characteristic remanences dispersed around a great circle subparallel to the regional schistosity and magnetic foliations. Late stress effects rotated paleoremanences into this pattern; we discount deflection of the paleofield by anisotropy. The pattern of dispersal indicates uniaxial oblate flattening of the region with NNW-SSE shortening, late in the metamorphic cooling history (<300°C). This postdates schistosity, AMS and AARM fabrics but it is controlled by the same kinematic pattern.