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首页> 外文期刊>Ore Geology Reviews: Journal for Comprehensive Studies of Ore Genesis and Ore Exploration >Geology, geochemistry, fluid inclusion characteristics, and U-Pb age studies on iron oxide-Cu-Au deposits in the Kolari region, northern Finland
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Geology, geochemistry, fluid inclusion characteristics, and U-Pb age studies on iron oxide-Cu-Au deposits in the Kolari region, northern Finland

机译：芬兰北部科拉里地区氧化铁-铜-金矿床的地质，地球化学，流体包裹体特征和U-Pb年龄研究

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Several iron oxide-copper-gold deposits are known in the Kolari region, in the western part of the Central Lapland greenstone belt, northern Finland. They are hosted by clinopyroxene-dominated skarns that were formed near to contact zone between ca. 1860 Ma Haparanda Suite intrusions and >2050 Ma Savukoski Group supracrustal rocks. All deposits are located within or next to shear and fault zones forming parts of the major, NNE-trending, Kolari shear zone. Three of the Fe-Cu-Au deposits, Kuervitikko, Cu-Rautuvaara, and Laurinoja were studied; all contain significant amounts of Cu (0.1 percent to 4.5 percent) and Au (0.1 to 6.6 ppm). At Laurinoja and Kuervitikko, Cu and Au are hosted by ironstone and skarn. At Cu-Rautuvaara, the host rock is a magnetite-disseminated albitite. The deposits have a distinct metal association of Fe-Cu-Au +- Ag, Bi, Ba, Co, Mo, Sb, Se, Te, Th, U, LREE. The wall and host rocks are intensely altered and display a deposit-scale zonal pattern. The distal alteration zone is characterised by albite +- biotite, K-feldspar, and scapolite and the proximal zone by clinopyroxene-magnetite +- amphibole, scapolite, calcite, and sulphides. Mass balance calculations indicate that Al_2O_3, TiO_2, and Zr were immobile during alteration. The calculations also indicate that significant quantities of Fe_2O_3, CaO, CO_2, S, Cu, Au, Bi, and Te were added to the proximal altered rocks. The main gains in the distal altered rocks are in Na_2O, K_2O, and Ba. Fluid inclusion data suggest that the fluids which circulated in the rocks during the main mineralisation event and subsequent brittle fracturing were highly saline (< 56 wt. percent NaCl) H_2O +- CO_2 fluids. The temperature during the main mineralisation event was between 450 and 550 deg C and the pressure was 1.5 to 3.5 kbar. Based on U-Pb age data of magmatic zircon from altered hanging wall diorite and granite that brecciates the ore, the age of the deposits is between 1864 +- 5 and 1766 +- 5 Ma. The 1797 +- 5 Ma age of zircon in skarn, combined with the 1810 to 1780 Ma ages of the metamorphic titanite in altered wall rocks and skarn, suggest that the deposits were most likely formed ca. 1800 Ma. This age has been interpreted to be broadly contemporaneous with the D_3 thrusting event in the Kolari region during which the Kolari shear zone was activated. The data presented in this work are inconsistent with previously proposed models for the Kolari deposits that they are metamorphosed syngenetic iron formations, or skarns related to ca. 1860 Ma monzonite intrusions. Instead, we propose that the Kolari Fe-Cu-Au deposits are of metasomatic replacement-type, and are controlled by the Kolari shear zone structures related to post-peak metamorphic D_3 thrusting event in northern Finland. Our data suggest that the Kolari deposits best fit into the category of epigenetic iron oxide-copper-gold mineralisation.
机译：在芬兰北部拉普兰中部绿岩带西部的科拉里地区，已知有一些氧化铁-铜-金矿床。它们由在附近的接触区附近形成的斜柏基主导的矽卡岩寄主。 1860 Ma Haparanda Suite侵入岩和> 2050 Ma Savukoski组上壳岩。所有矿床都位于剪切和断层带之内或附近，形成了主要的，近东近东趋势的科拉里剪切带。研究了三个Fe-Cu-Au矿床，Kuervitikko，Cu-Rautuvaara和Laurinoja。它们都含有大量的铜（0.1％至4.5％）和金（0.1至6.6 ppm）。在Laurinoja和Kuervitikko，铜和金由铁矿石和矽卡岩组成。在Cu-Rautuvaara，基质岩石是磁铁矿弥散的方铁矿。该沉积物具有Fe-Cu-Au +-Ag，Bi，Ba，Co，Mo，Sb，Se，Te，Th，U，LREE的独特金属缔合。围岩和主体岩石发生强烈变化，并显示出沉积规模的纬向格局。远端蚀变带的特征是钠长石+-黑云母，钾长石和闪锌矿，而近端蚀变带的特征是斜辉石-磁铁矿+-闪石，闪锌矿，方解石和硫化物。质量平衡计算表明，Al_2O_3，TiO_2和Zr在蚀变过程中不动。计算还表明，向近蚀蚀变岩石中添加了大量的Fe_2O_3，CaO，CO_2，S，Cu，Au，Bi和Te。远端蚀变岩石的主要增产是在Na_2O，K_2O和Ba中。流体包裹体数据表明，在主要矿化事件和随后的脆性压裂过程中在岩石中循环的流体是高盐度（NaCl含量小于56％）的H_2O + -CO_2流体。主要矿化过程中的温度在450至550摄氏度之间，压力为1.5至3.5千巴。根据角铁矿石中角砾岩和花岗岩的蚀变后的岩浆锆石的U-Pb年龄数据，矿床年龄在1864±5至1766±5 Ma之间。矽卡岩中的锆石年龄为1797±5 Ma，再加上蚀变的围岩和矽卡岩中的变质钛矿的1810至1780 Ma年龄，表明该沉积物最有可能形成于大约。 1800马该年龄已被解释为与激活Kolari剪切带的Kolari地区的D_3逆冲事件大致相同。这项工作中提出的数据与先前提出的Kolari矿床模型不一致，因为它们是变质的同生铁形成，或与约克山有关的矽卡岩。 1860年Ma巨型岩侵入。取而代之的是，我们认为科拉里铁铜金矿床属于交代置换型，并受与芬兰北部峰后变质D_3逆冲事件有关的科拉里剪切带结构的控制。我们的数据表明，Kolari矿床最适合表观成因的氧化铁-铜-金矿化。

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