摘要
元古代，夹持于现今安宁河－元谋深断裂与小江深断裂之间的地区，是扬子古大陆的边缘裂谷，本文以“康滇裂谷带”命名。研究结果表明，该区广泛发育的元古代碱性（钠质）火山岩系列及细碧－角斑岩类火山岩组合，是裂谷火山活动的产物，火山活动时限１９５０～９００Ｍａ，可划分为大红山群及昆阳群两个火山旋回。火山岩系多属碱性玄武岩系列，火山活动的中晚期，分异出少量亚碱性拉斑玄武岩系列和高铝玄武岩系列。裂谷带火山喷发区地壳厚度１２～５０ｋｍ，岩浆来源深度为２７０～１００ｋｍ，形成温度约１２１３～１１６３℃。熔浆来源于慢源，可能是玄武岩浆分异的、富挥发分富钠质的“派生岩浆”。
The area between Anninghe-Yuanmou Deep Fault and Xiao-jiang Deep Fault was the marginal rift of Yangzi Old Land in Proterozoic, which is called 'Kang-Dian Rift Zone' in this paper. The study result shows that the Proterozoic alkalic (sodic) volcanic rock series and spilite-keratophyre assemblage well developed in this area are formed by the rift volcanism. The volcanism age is 1950900Ma, which can be divided into two volcanic cycles belonging to Dahongshan Group and Kunyang Group. The volcanic rock series mainly belong to alkalic basalt series. However, a small amount of subakalic tholeiite series and high-alumina basalt series are formed by differentiation in the middle-late period of the volcanism. The crust thickness of volcanic eruption area in the rift zone is 12-50 km , the depth of the magma origin is 270-100 km, and the formation temperature is about 1213-1163℃. The magma is originated from the mantle and maybe the 'derivative magma' rich in volatile and sodium, formed by the differentiation of basalt magma.
出处
《云南地质》
1995年第2期81-98,共18页
Yunnan Geology
