The Early Paleoproterozoic Monchegorsk layered mafite-ultramafite massif in the Kola Peninsula: Geology, petrology, and ore potential
The Early Paleoproterozoic Monchegorsk layered mafite-ultramafite massif in the Kola Peninsula: Geology, petrology, and ore potential
复制标题
科拉半岛早古元古代 Monchegorsk 层状镁铁矿-超镁铁矿地块：地质学、岩石学和矿石潜力
作者：
E. Sharkov;A. Chistyakov
摘要：早古元古代蒙切戈尔斯克杂岩体出露面积达 550 km2，由两层不同年龄的镁铁矿-超镁铁矿侵入体组成：由超镁铁质和镁铁质岩组成的蒙切戈尔斯克岩体和以辉长岩为主的主山脉地块（也称为蒙恰-楚纳-沃尔奇苔原地块），二者由断层隔开。两个地块均由夹层堆积物组成（首先，Ol ± Crt、Ol + Opx ± Crt、Opx、Opx + Pl ± Cpx 和 Pl），它们是由相似的硅质高镁系列熔体产生的，但其堆积物的地层学有所不同：Monchegorsk 岩体主要由超镁铁矿组成，而主山脉地块主要由辉长岩组成，首先是辉长岩。该杂岩体伴有PGE-Cu-Ni矿化、低硫化物Pt-Pd矿化和铬铁矿矿化。从地质数据和同位素日期来看，Monchegorsk 杂岩是一个长寿的岩浆中心，其演化时间跨度为 50 Myr，时间跨度为 2.50–2.46 Ga。主山脉地块更年轻，可能截断了 Monchegorsk 岩体的西部延续。该杂岩体在空间上仅限于中古元古代区域中央科拉断层区域，现在是构造拼贴，其岩石在变形过程中受到叠印变质作用的不同影响。这些过程对南部蒙切戈尔斯克岩体周边的岩石影响最为显着。这些岩石在绿片岩相条件下完全转变，但通常保留其原始纹理和结构。这些过程覆盖了岩体本身的边缘部分及其第二阶段的岩石，并伴随着经济的低硫化物铂族元素矿床。 Monchegorsk 杂岩的 PGE-Cu-Ni 矿石矿化在遗传上与两个不同的进化事件相关，中间有一个静止期：
(1)大型层状镁铁矿-超铁矿侵入体就位于2.5~2.45 Ga。Monchegorsk岩体内存在具有次级PGE矿化的硫化物铜镍矿经济矿床，中品位低硫化物PGE矿与其第二演化阶段(Vuruchuaivench山麓、Moroshkovoe湖和Southern Sopcha地区)有关。原生岩浆矿化主要为Cu-Fe-Ni硫化物和PGE铋碲化物。(2)Monchegorsk杂岩体卷入2.0~1.9 Ga的中央科拉断层带，破碎于构造块拼贴中。岩石沿着块体边界被剪切，并受到叠印变质作用的影响，变质作用是在南部 Monchegorsk 岩体周围的构造的绿片岩相条件下进行的。从而使原生PGE-Cu-Ni矿化物经历了变质过程，并发生重结晶，形成Pt-Pd砷化物、锡化物、锑化物、硒化物等。这一过程与PGE的局部积累（达到经济集中度）的部分重新分布有关，并且矿体本身获得了弥漫的轮廓。换句话说，第二幕的标志是较古老的原生岩浆矿化的转变。
AbstractThe Early Paleoproterozoic Monchegorsk Complex is exposed over an area of 550 km2 and comprises two layered mafite-ultramafite intrusions of different age: the Monchegorsk pluton of ultramafic and mafic rocks and the predominantly gabbroid Main Range Massif (also referred to as the Moncha-Chuna-Volch’i Tundras Massif), which are separated by a fault. Both massifs consists of intercalating cumulates (first of all, Ol ± Crt, Ol + Opx ± Crt, Opx, Opx + Pl ± Cpx, and Pl), they were produced by similar melts of siliceous high-Mg series but differ in the stratigraphy of their cumulates: while the Monchegorsk pluton is dominated by ultramafites, the Main Range Massif consists mostly of gabbroids, first of all, of gabbronorites. The complex is accompanied by PGE-Cu-Ni ore mineralization, low-sulfide Pt-Pd mineralization, and chromite mineralization. Judging from geological data and isotopic dates, the Monchegorsk Complex is a long-lived magmatic center, which evolved over a time span of 50 Myr at 2.50–2.46 Ga. The Main Range Massif is younger and likely truncates the western continuation of the Monchegorsk pluton. The complex is spatially restricted to the zone of the Middle Paleoproterozoic regional Central Kola Fault and is now tectonic collage whose rocks were variably affected by overprinted metamorphism in the course of deformations. These processes most significantly affected rocks along the peripheries of the Monchegorsk pluton in the south. These rocks were completely transformed under greenschist-facies conditions but often preserved their primary textures and structures. The processes overprinted both the marginal portions of the pluton itself and the rocks of its second phase, which are accompanied by economic low-sulfide PGE deposits. The PGE-Cu-Ni ore mineralization of the Monchegorsk Complex is genetically related to two distinct evolutionary episodes with a quiescence period in between:
(1)The emplacement of large layered mafite-ultramafite intrusions at 2.5–2.45 Ga. Economic deposits of sulfide Cu-Ni ores with subordinate PGE mineralization occur within the Monchegorsk pluton, and the moderate-grade low-sulfide PGE ores are related to its second evolutionary phase (in the foothills of Vuruchuaivench and in the Moroshkovoe Lake, and Southern Sopcha areas). The primary magmatic ore mineralization is predominantly Cu-Fe-Ni sulfide with PGE bismuthides-tellurides.(2)The Monchegorsk Complex was involved in the zone of the Central Kola Fault at 2.0–1.9 Ga and was broken in a collage of tectonic blocks. The rocks were sheared along the boundaries of the blocks and were affected by overprinted metamorphism, which proceeded under greenschist-facies conditions in the structures surrounding the Monchegorsk pluton in the south. Thereby the primary PGE-Cu-Ni ore mineralization underwent metamorphic processes was recrystallized with the formation of Pt-Pd arsenides, stannides, antimonides, selenides, etc. This processes was associated with the partial redistribution of PGE with their local accumulation (up to economic concentrations), and the orebodies themselves acquired diffuse outlines. In other words, the second episode was marked by the transformation of the older primary magmatic ore mineralization.