摘要
冷口变质火山岩为较典型的双峰式火山岩，以变质基性火山岩为主，夹变质英安质岩石。依据元素地球化学和同位素地球化学分析，它应形成于大陆或大陆边缘裂谷环境。基性岩浆来源于亏损地幔，岩浆在侵位过程中受到强烈的地壳成分混杂作用改造，而英安质岩石可能是由大陆地壳部分熔融作用形成的。
The Lengkou metamorphic volcanics as main part of super-crust rocks in Shushui Comolex croup out in Lengkou village, northern Zhongtiao Mis, which is composed of metamorphic basic volcanics (biotite schists, hornblend-biotite schists, scapolite-biotite schists and amphibolites) interlayered with metamorphic dacitic rocks. It is occurred with bimodal structure. The Lengkou meta-volcanics is daced by single zircon U-Pb and ion probe, whole rock Sm-Nd and Rb-Sr isochron methods and given the 2 350 Ma for crystallization age. The Lengkou basic volcanics are calcalkaline rocks. Its main geochemical characteristics show enrichment of Sr, K, Rb, Ba and Ce and depletion of Ti, Y, Yb, Ta and Nb, which is due to the contamination of crust to basic magma derieved from the depleted mantle. The REE patterns of Lengkou basic rocks are highly fractioned ones and with lower Sm/Nd ratioes. COmbined with Nd and Sr isotopic geochemistry, the basic volcanics were formed in the rift of continent or continetal margin.Lengkou dacitic rocks are high Al2O3 ones with calcalkaline character. The high Al2O3, K2O, Zr, La, Ce, and K/Rb ratioes and low Yb content as well as highly fracoioned REE patterns suggested it formed in continental rift. It is supported by lower 143Nd/144Nd and higher 87Sr/86Sr ratioes.
关键词
涑水杂岩
火山岩
地球化学
Lengkou metamorphic volcanics
continental rift
depleted mantle
custal
contamination
