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首页> 外文期刊>Economic geology and the bulletin of the Society of Economic Geologists >U-Pb DATING OF A DIABASE DIKE RESOLVES THE PROBLEM OF MUTUALLY CROSSCUTTING RELATIONSHIPS WITHIN THE FRASER-STRATHCONA DEEP COPPER VEIN SYSTEM, SUDBURY BASIN
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U-Pb DATING OF A DIABASE DIKE RESOLVES THE PROBLEM OF MUTUALLY CROSSCUTTING RELATIONSHIPS WITHIN THE FRASER-STRATHCONA DEEP COPPER VEIN SYSTEM, SUDBURY BASIN

机译：DIABASE DIKE的U-Pb约会解决了弗拉斯堡-斯特拉肯纳深铜脉系统（跨盆地）中相互交叉关系的问题

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A geologic problem has been addressed in the Fraser-Strathcona Deep Copper mine, Sudbury, wherein diabase dikes and the chalcopyrite vein system have a mutually crosscutting relationship. In any situation where orosscutting relationships are mutual there is ambiguity, and it is important to independently test and verify the ages of the events in question, thus avoiding erroneous conclusions about the controls on mineralization. To this end detailed underground geologic mapping and U-Pb dating have been applied to a diabase dike that crosscuts the 1850 Ma Sudbury Igneous Complex and footwall Cu-Ni-PGE vein mineralization. The dike has a minimum 1.5 km strike length, 2.2 km dip length, and a width of 20 m. Where the dike cuts the Cu-Ni-PGE vein system there are (1) sharp contacts with the dike clearly cutting chalcopyrite veins, (2) laminated chalcopyrite-pyrrhotite-pentlandite veins along the hanging-wall or footwall contacts of the dike, and (3) back veining in the form of 0.5- to 2 m-wide remobilized sulfide veins and stockworks that cut the dike. Magmatic zircons from the diabase have a concordant ~(206)Pb/~(238)U age of 506 +- 4 Ma, whereas abundant xenocrystic zircons have ages of 1810 to 1840 Ma and appear to have been derived from the Sudbury Igneous Complex. Magmatic titanite from the dike defines a highly discordant array of points with an upper intercept at 530 +- 21 Ma, although the titanite analyses are not precise. The discordance results from recent Pb loss, which may have been related to brittle fracturing and fluid infiltration during exhumation and mild deformation. The diabase dike is interpreted to be part of the 500 to 600 Ma extension and rifting that formed the Ottawa-Bonnechere graben and related features during rifting of eastern North America prior to the opening of the lapetus Ocean. It represents the youngest intrusive event within the post-impact geologic history of the Sudbury structure.
机译：萨德伯里的弗雷泽-斯特拉科纳深铜矿已经解决了地质问题，其中辉绿岩堤防和黄铜矿脉系统具有相互交叉的关系。在相互联系的任何情况下都存在歧义，重要的是要独立测试和验证所讨论事件的年龄，从而避免关于控制矿化的错误结论。为此，详细的地下地质测绘和U-Pb测年法已应用于辉绿岩堤坝，该堤坝横切了1850年的Ma Sudbury火成岩和下盘Cu-Ni-PGE脉矿化。堤防的最小罢工长度为1.5公里，倾角长度为2.2公里，宽度为20 m。堤坝切割Cu-Ni-PGE静脉系统的地方（1）与堤坝形成鲜明的接触，清楚地切割了黄铜矿脉;（2）沿堤坝的吊壁或底壁接触层状的黄铜矿-蛇绿铁矿-膨润土脉动，以及（3）以0.5到2 m宽的固定硫化物静脉和切断堤坝的仓库形式出现的背部静脉。辉绿岩中的岩浆锆石的〜（206）Pb /〜（238）U年龄一致，为506±4 Ma，而丰富的异晶锆石的年龄为1810至1840 Ma，似乎源自萨德伯里火成岩。堤防中的岩浆钛矿定义了高度不协调的点阵列，其最高截距为530±21 Ma，尽管钛矿分析并不精确。不一致是由于最近的铅损失引起的，这可能与掘尸和轻微变形期间的脆性破裂和流体渗透有关。辉绿岩堤坝被认为是500到600 Ma延伸和裂谷的一部分，该裂谷形成了渥太华-邦纳切尔河grab石和相关特征，在北美东部东部裂谷开放之前就形成了裂谷。它代表了萨德伯里结构撞击后地质历史中最年轻的侵入事件。

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