Ural-Alaskan type complexes are the sources for unique placer platinum deposits and contain platinum-group minerals (PGM) within lodes. Such complexes occur along modern and ancient convergent tectonic margins and are comprised of dunite, wehrlite, clinopyroxenite and gabbro, which gradually interchange towards the marginal parts of the complex. In-situ PGM are largely restricted to chromitites, which are comprised of small veinlets and schlieren of chromian spinel in the dunite unit. PGM mineralization in chromitites can be extremely rich; however, their distribution is very sporadic, without any apparent regularity. Moreover, the role of accessory chromian spinel and post-magmatic overprinting of platinum group element (PGE) concentrations is poorly defined. Detailed studies of PGM assemblages, including those in chromitites, serpentine veinlets in dunites, and wehrlites, combined with PGE geochemistry could provide insights into the distribution and processes responsible for PGE accumulation.

The Matysken complex in the Koryak Highlands (Far East Russia) is comprised of dunite, wehrlite, clinopyroxenite and gabbro units, and has a classic zoned structure, rendering it an excellent example of an Ural-Alaskan type complex, ideal for this case study. This locality contains mm-scale isoferroplatinum (Pt₃Fe) nuggets that cement chromitites and occur as µm-scale euhedral inclusions in chromian spinel. Placer PGM assemblages in the nearby Matysken River consist of exactly the same assemblages of minerals that are found in dunites and chromitites but with larger compositional scatter, reflecting a complex history of alluvium accumulation, which was sourced from different eroded parts of the complex. Detailed textural investigations discovered a diverse array of hydrous silicate–related mineralization, including euhedral isoferroplatinum grains in chlorite matrix, isoferroplatinum–amphibole intergrowths, and a wide range of PGE, Fe and Cu alloys, sulfarsenides and antimonides, which formed in serpentine veinlets together with awaruite (Ni₃Fe) and base metal sulfides. This provides further evidence that isoferroplatinum, which is widely accepted to be a magmatic mineral, may form under a wide range of conditions, including during serpentinization.

Dunites have fractioned primitive mantle-normalized PGE patterns, typical of Ural-Alaskan type complexes, with strong enrichments in Pt and depletions in Ir, Ru and Pd. PGE, with an exception of Pd, are quite uniformly distributed in dunite containing accessory chromian spinel, with good correlations between PGE and Cr. This correlation, together with data from previous studies, allowed us to calculate the concentration of Pt in accessory chromian spinel (probably hosted as minute PGM inclusions), which is of the same grade as for chromitites (ppm levels). This suggests that the formation of chromitites does not concentrate PGE over Cr, but only assembles them into larger aggregates, causing the observed unevenness in the PGM distribution.

乌拉尔-阿拉斯加类型的络合物是独特的砂金矿床的来源，并且在矿脉中含有铂族矿物质（PGM）。这些复合物沿现代和古代的汇聚构造边缘而生，由榴辉岩，辉绿岩，斜辉石和辉长岩组成，它们逐渐向复合物的边缘部分交换。原位PGM主要限于铬铁矿，该铬铁矿由小脉状和在榴辉岩单元中的铬尖晶石的铁屑组成。铬铁矿中的PGM矿化可能非常丰富；但是，它们的分布非常零散，没有任何明显的规律性。此外，对副铬尖晶石和铂族元素（PGE）浓度的岩浆后叠印的作用定义不清。对PGM组件（包括铬铁矿中的组件）的详细研究，

Koryak高地（俄罗斯远东地区）的Matysken建筑群由榴辉岩，白云母，斜辉石和辉长岩组成，并具有经典的分区结构，使其成为Ural-Alaskan型建筑群的典范，非常适合此案例研究。该位置包含毫米级的异铁铂（Pt ₃Fe）形成铬铁矿的铬块，并以铬铁皮尖晶石中微米级的正方内含物形式存在。邻近的Matysken河中的砂矿PGM组合物与在辉长岩和铬铁矿中发现的矿物质组合完全相同，但具有较大的成分散布，反映出复杂的冲积层积聚历史，其源于该复合物的不同侵蚀部位。详细的组织学调查发现，与水合硅酸盐有关的矿化作用多种多样，包括亚氯酸盐基质中的正金属异铁铂颗粒，异铁铂-安瓿共生体以及各种PGE，Fe和Cu合金，硫代砷化物和锑化物，它们在蛇形细矿中形成，并与蛇纹石一起形成。淡褐色（Ni ₃铁）和贱金属硫化物。这提供了进一步的证据，即被广泛认为是岩浆矿物的异铁铂可能在多种条件下形成，包括在蛇纹石化过程中。

ites石具有原始的地幔归一化PGE模式，这是Ural-Alaskan型复合物的典型特征，Pt含量高，Ir，Ru和Pd含量低。除Pd外，PGE在含辉石尖晶石的辉光岩中分布均匀，在PGE和Cr之间具有良好的相关性。这种相关性，再加上以前的研究数据，使我们能够计算出副铬尖晶石中的Pt浓度（可能是微小的PGM夹杂物），与铬铁矿的品位相同（ppm级）。这表明铬铁矿的形成不会使PGE集中在Cr之上，而只会将它们组装成更大的聚集体，从而导致在PGM分布中观察到不均匀性。