【摘要】 1998年开展的马池幅1∶5万区调项目,在石泉县—马岭关一带发现一套中浅变质火山杂岩系。通过调查:( 1 )该套变质火山岩系是由大小不等的元古界变质中基—酸性火山岩、变质沉积岩、变质古侵入岩、早古生代脉岩及下古生界变质沉积岩等岩块或岩楔组成,经多期、多级韧性剪切带、脆性断裂分划拼贴形成,呈菱形交织网状岩片拼贴带展布而具构造混杂岩带属性;( 2 )地球化学研究显示,该杂岩中变质火山岩包容有洋溢拉斑玄武岩、岛弧拉斑玄武岩、弧后盆地拉斑玄武岩及板内玄武岩、盖层变质沉积岩等组合,胭脂沟府冲型古侵入岩体侵入其中;( 3)该变质火山岩系夹持于马岭关构造带中,南、北边界分别由推覆构造、剥离断层及断裂构造限定,向西延交于饶峰—麻柳坝断裂带中;向东延伸于茨沟—吕河一线;( 4 )在酸性火山岩中获得1 70 0±1 2Ma (锆石U -Pb)同位素测年值和547±1 4Ma变质年龄值。上述表明马岭关杂岩属一套包容形成于不同构造环境、不同岩类,以多级骨架构造分划、拼贴组成的构造混杂岩,其物质组成复杂,岩浆作用、地质构造演化与古勉略构造带相近,并构成分划南秦岭微地块与凤凰山构造过渡基底的分区界线,应属古勉略构造带的构造物质组成。更多还原

【Abstract】 Regional geological survey of the Machi quadrangle at 1∶50,000 discovered a set of moderate-epimetamorphic volcano complex in the Malingguan area of Shiquan County. The geological survey has concluded that: 1) the complex consists of the Proterozoic metamorphosed intermediate basic-acidity volcanics, metamorphosed sediments, metamorphosed paleo-intrusions, the early Paleozoic dikes, and blocks and sphenolith of the lower Paleozoic metamorphosed sediments. It was formed by division and mosaic of multiphase and multistage shear zones and brittle fractures and is distributed in mosaic belts of rhombus interlocking microlithon with the property of tectonic mélange; 2) the complex rocks are intercalated in the Malingguan structural zones, of which the south and north boundaries are nappe structure, stripped faults and faulted structures. To the west, it is in conjunction with the Raofeng-Maliuba faulted zones and to the east, it extends along a line between Cigou and Luhe; 3) geochemistry research has indicated that the metamorphosed volcanics in the complex contains tholeiite, arc-tholeiite, back-arc tholeiite and the composition of basalt in-plate and metamorphosed sediments in cover rocks, in which the Yanzhigou subducting intrusive rocks exist. 4) isotopic dating (Zr and U-Pb), from the acidity volcanics, attained 1,700+12Ma and the metamorphic age 547+14Ma. The researches above have indicated that the Malingguan complex was formed in different structural environments with different rocks, which is structural complex through mosaic and structural divisions at multiple frameworks. The materials in the complex are complicated, in which the magmatic activities, and tectonic evolution are similar to that occurring in old Mianxian-Lueyang structural zone, which formed a boundary between the southern Qinling micro-block and the transitional basement of the Fenghuangshan structures, belong to the components of the structural material in the old Mianxian-Lueyang structural zone.更多还原