Paleomagnetism of the Grum Zn-Pb-Ag deposit, Selwyn Basin, Yukon, Canada
Paleomagnetism of the Grum Zn-Pb-Ag deposit, Selwyn Basin, Yukon, Canada
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加拿大育空地区塞尔文盆地格鲁姆锌铅银矿床的古地磁学
DOI：
10.1139/cjes-2021-0114
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发表时间：
2023
影响因子：
1.4
通讯作者：
Symons David T.A.
中科院分区：
文献类型：
--
作者：
Kawasaki Kazuo;Symons David T.A.
格鲁姆矿床是育空塞尔文盆地Anvil地区以碎屑岩为主的五个大型锌铅银矿床之一。Grum的矿化赋存于晚元古代至寒武纪麦山组与寒武纪至早奥陶世Vangorda组的接触部位。对Grum露天矿15个矿化点的113个样品进行了古地磁分析，确定了Grum的成矿年龄。这些分析分离出稳定的特征剩磁(ChRM)，主要是通过热退磁，然后是交变磁场退磁。CHRM的主要载体是单一或假单域磁黄铁矿和少量磁铁矿，其古极点位于北纬67.8°，东经317.4°(95%置信度的圆锥体半径，A95=77.2°)。在顺时针旋转并向北平移盆地以最符合北美视极漂移路径后，古极点得出Grum矿床的年龄为176 Ma±212 Ma。因此，锌铅银花岗岩成矿作用明显早于附近中白垩世钉子岩基的侵入，但与塞尔文盆地广泛的早侏罗世变质作用同时代，与早侏罗世山间带地体与北美克拉通的碰撞有关。
The Grum deposit is one of five large clastic-dominated Zn–Pb–Ag deposits in the Anvil district of the Selwyn Basin, Yukon. Grum’s mineralization occurs at the contact between the late Proterozoic to Cambrian Mount Mye Formation and the Cambrian to Early Ordovician Vangorda Formation. Paleomagnetic analyses of 113 specimens from 15 mineralized sites in the Grum open pit were undertaken to date Grum’s mineralization. The analyses isolated a stable characteristic remanent magnetization (ChRM), mostly by thermal and then alternating field demagnetization. The main ChRM carrier is single- or pseudosingle-domain pyrrhotite with minor magnetite that give a paleopole at 67.8°N latitude and 317.4°E longitude (radius of the cone of 95% confidence,A95= 7.2°). The paleopole yields an age of 176 ± 12 Ma for the Grum deposit after a clockwise rotation and northward translation of the basin to best fit the North American apparent polar wander path. Thus, the Zn–Pb–Ag Grum mineralization significantly predates intrusion of the nearby mid-Cretaceous Anvil Batholith, but is coeval with widespread Early Jurassic metamorphism in the Selwyn Basin that correlates with the Early Jurassic collision of the Intermontane Belt terranes with the North America craton.