Laramide orogenic fluid flow into the Western Canada sedimentary basin; evidence from paleomagnetic dating of the Kicking Horse mississippi valley-type ore deposit
Laramide orogenic fluid flow into the Western Canada sedimentary basin; evidence from paleomagnetic dating of the Kicking Horse mississippi valley-type ore deposit
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DOI：
10.2113/gsecongeo.93.1.68
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发表时间：
1998-02
期刊：
影响因子：
5.8
通讯作者：
D. Symons;M. Lewchuk;D. Sangster
中科院分区：
文献类型：
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作者：
D. Symons;M. Lewchuk;D. Sangster
踢马和帝王密西西比河谷型锌铅矿床位于加拿大不列颠哥伦比亚省科迪勒拉山脉前陆带的落基山脉南部。这些后生闪锌矿-方铅矿矿床位于加拿大西部沉积盆地西南缘大教堂组中寒武统白云岩中的一块巨大的亮晶白云岩片中。这些地层在拉拉米德造山运动期间发生褶皱、逆冲断层和隆起。使用交变场和热阶退磁以及等温剩磁方法，对来自 32 个矿化和主岩地点的 316 个样本进行了古地磁分析。结果表明，磁黄铁矿和磁铁矿均具有特征剩磁。密西西比河谷型矿化附近特征剩磁强度的增加将磁化强度与矿化事件联系在一起。小尺度（约 10 m）和大尺度（约 10 km）的褶皱测试表明，特征剩磁化强度晚于主要的 Laramide 变形事件。特征剩磁方向的比较表明，当矿化体具有一次特征剩磁时，围岩发生了再磁化。 Kicking Horse 矿化和邻近的主岩构成了该集合体的大部分，并给出了晚白垩世的极位置：北纬 64.0 度，西经 152.8 度（95% 置信度的椭圆形半轴：δ p = 5.4 度，δ m = 5.8 度；地点（样本）数量 = 19 (180)）。该磁极的年龄与白垩纪正常超年代一致，并且符合除一个具有相反方向的样本之外的所有正常特征剩磁方向的发现。没有任何地点保留拉拉米德造山运动之前的特征性剩磁。回顾了加拿大西部沉积盆地拉拉米德之前密西西比河谷型矿化和白云石化事件的证据，得出盆地内主要流体流动事件发生在晚白垩世-古新世拉拉米德造山运动期间。
The Kicking Horse and Monarch Mississippi Valley-type zinc-lead ore deposits are in the southern Rocky Mountains of the foreland belt in the Canadian Cordillera of British Columbia. These epigenetic sphalerite-galena deposits are hosted by a massive sparry dolomite sheet in Middle Cambrian dolostones of the Cathedral Formation on the southwestern margin of the western Canada sedimentary basin. These strata were folded, thrust faulted, and uplifted during the Laramide orogeny. Paleomagnetic analysis was done on 316 specimens from 32 mineralized and host-rock sites, using alternating field and thermal step demagnetization and isothermal remanence methods. The results show that the characteristic remanent magnetization is carried by both pyrrhotite and magnetite. The increase in characteristic remanent magnetization intensity near Mississippi Valley-type mineralization ties the magnetization to the mineralization event. Fold tests on a small scale ( approximately 10 m) and a large scale ( approximately 10 km) show that the characteristic remanent magnetization postdates the main Laramide deformation event. Comparison of the characteristic remanent magnetization directions shows that the host rocks were remagnetized when the mineralization was emplaced with a primary characteristic remanent magnetization. The Kicking Horse mineralization and adjacent host rocks form the bulk of the collection and give a Late Cretaceous pole position of 64.0 degrees N, 152.8 degrees W (semi-axes of oval of 95% confidence: delta p = 5.4 degrees , delta m = 5.8 degrees ; number of sites (specimens) = 19 (180)). The age of this pole coincides with the Cretaceous normal superchron and conforms to the finding of all normal characteristic remanent magnetization directions except for one sample with an antipodal direction. No site retains a characteristic remanent magnetization that predates the Laramide orogeny. The evidence for and against a pre-Laramide Mississippi Valley-type mineralizing and dolomitizing event in the western Canada sedimentary basin is reviewed, and it is concluded that the main fluid flow event in the basin occurred during the Late Cretaceous-Paleocene Laramide orogeny.