郭家岭岩体壳幔岩浆混合作用与侵位机制的动力学研究

暗色包体、岩石地球化学及Nd.Sr同位素的研究一致表明,胶东金矿区的郭家岭岩体是由壳幔岩浆混合形成的,混合比大体为3:2.该岩体岩性均一,缺少长英质端元和过渡性岩石类型正是壳幔岩浆混合程度高的表现。以胶东群地层150MPa.850℃条件下的部分熔融产物(熔体分数约35%)作为长英质端元,最偏基性的闪长质包体作镁铁质端元,按3:2的混合比较好地模拟了该岩体的成分,同时也满足了分层岩浆房发生整体对流的动力学条件。根据暗色包体计算了岩体的侵位速度,结果表明该岩体很可能是沿着现在的艾山岩体所占据的断裂通道侵位的。岩体呈EW向带状产出反映了基底构造——栖霞复背斜对该岩体形成的控制作用。

DYNAMIC STUDY ON THE CRUSTAL-MANTLE MAGMA MIXING AND EMPLACEMENT MECHANISM OF GUOJIALING GRANITE

Trap enclaves, petrntgeochemisby and Nd, Sr isotope studies all indicate that the Guojialing granite in the Jiaodong gold zone wasformed from the mixture of crustal-mantle magmas with a mixing ratio of about 3:2. ln the end stage of lndosinian movement in Mesozoic erat Jiaodong region came into crusbelaxing period after collision oregenesis. The uplifing of mantle magma caused panial meldng of the Jiaodong Group metamorphosed basement, and followed by a extensive interaction of two magmas. In the early stage of the interaction, small arnount of basic magma (about 5%) entered felsic magma and subjected to rapid quenching which prevented two magmas from fumher component exchange. Therefore, they were preserved as trap enclaves in the host granite. Thehomogeneous lithology and the lack of felsic end member and tmnsidonal stocks in the grudte only reflect a very high mixing degree of crustmantle magmas, which characterizes a convection mixingin a magma charnber. Taldng the pardal melt of Jiaodong Group strataunder 150MPa, 850℃ (melt fraction of about 35%) as felsic end member and the most basic enclaves as mafic end member. We successfully model thecomposidon of the granite following the mdxing rado of 3: 2, meanwhilethe model meats the dynamic conditions of whole convection in a layered magma chamber. The calculation results of the emplacement rates show that the granite was emplaced along the fault conduit that prescndy is occupied by Aishan granite, The occurrence of the granite as a EVfttending belt batholith is mainly controlled by the brement structure-Qixia andclinoriurn.