东准噶尔玛因鄂博地区增生楔中基性混杂岩块地球化学特征及构造环境探讨

东准噶尔玛因鄂博地区发育一典型的小型增生楔，增生楔中辉长岩岩块具有高铝（Al2O3：14．38％～16．33％），高钛（TiO2：1．81％～2．46％），贫钾（K2O：0．17％～0．63％）的地球化学特征。相对富集大离子亲石元素（Sr、K、Rb、Ba），高场强元素（Nb、Ta．Zr、Hf）没有明显的异常，源区具有类似于洋脊玄武岩的特征。基性岩块具有类似于E—MoRB和OIB的稀土元素配分形式，没有出现Nb、Ta、Ti的明显亏损，说明其形成过程中可能没有受到或受到较弱的消减带影响，综合上述认识，认为夹于增生楔中的此类基性岩块体很可能来源于洋壳俯冲过程中增生的海山残片；根据玛因鄂博增生楔物质组成特征以及前人的相关年代学证据表明该增生楔形成于古生代弧后盆地环境，在晚泥盆世之前形成俯冲增生杂岩体。

比鲁特构造岩浆混杂带特征

比鲁特构造岩浆混杂带分布于白云鄂博西北7Km的白云鄂博群哈拉霍圪特组、比鲁特组二、三段之间,总体呈北东东向展布,全长约6Km,宽约500—600m。向东与哈拉霍圪特组断层接触,向西被下白垩统固阳组覆盖。北与比鲁特组二、三段以北倾逆断层为界,南与比鲁特组断层接触。整体呈一构造岩片(带)出露在白云鄂博群中。

Deep-seated geodynamics and position of Platinum-bearing basite-ultrabasite massifs of southeast Russia

In the southeast part of the North-Asian craton, several ring basite-uhrabasite plutons have been rec- ognized, with which the commercial placers of platinoids associate. Analysis of the known geodynamic models of the region formation and materials of seismic tomography showed that the subduction processes, that actively manifested themselves in the Asia-Pacific convergence zone in Mesozoic, were responsible for initiation of the stagnated oceanic slab. Its NE and SW boundaries appear to coincide with the transform faults. Projection of the transform fault, bordering the above mentioned slab in the NEN, coincides with the Konder-Feklistovsky metal- logenic belt distinguished earlier and its Aldan （Inaglinsky） member. Higher platinum content of ring massifs of the belt is controlled by the influence of the lower mantle derivatives on the ascending upper mantle plumes.