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五河杂岩是华北克拉通东部陆块东南缘最重要的岩石单元。然而,直至今日,人们对于该组杂岩一直缺乏足够的研究,特别是对于其形成的变质条件分歧较大。本文通过对蒙城南ZK02钻孔中五河杂岩的构成和地质特征详细研究表明五河杂岩分为上、下两段。上段主要为一套由云母片岩、大理岩和花岗片麻岩组成的变质表壳岩系;下段为一套基性变质岩,主要岩性为斜长角闪岩、角闪岩、石榴斜长角闪岩和少量的混合岩。同时,针对下段特征岩石(石榴斜长角闪岩),进行了较为详细的岩相学和矿物化学分析,并应用不同的温压计进行P-T条件评价和比较,结合岩相学限定和前人的研究成果,认为五河杂岩的主体普遍经历了高压角闪岩相变质作用,其温压范围为:T=671℃~700℃和P=0.82~0.95GPa,地温梯度约为25~28℃/km,与典型陆壳地温梯度类似。与同邻区主要岩石单元的变质级别相比,五河杂岩应当形成于板内变质环境,并不具备造山带变质特征。
Wuhe Complex is the most important rock unit on the southeastern margin of the eastern block of North China Craton. However, until now, there has been a lack of sufficient research on this group of complexes, especially for the formation of metamorphic conditions. In this paper, a detailed study of the composition and geological characteristics of the Zhongwuhe complex in the ZK02 borehole in Mengcheng South shows that the Wuhe complex is divided into upper and lower sections. The upper section is mainly composed of metamorphic crustal rocks composed of micritoliths, marble and granitic gneiss. The lower section is a set of basic metamorphic rocks with the main lithologies of amphibolite, amphibolite, pomegranate Amphibolite and a small amount of mixed rock. At the same time, more detailed petrography and mineral chemical analysis were carried out for the lower characteristic rocks (porpholnite amphibolite), and PT conditions were evaluated and compared by using different thermometers. Combined with the definitions of lithofacies and predecessors , The author thinks that the main body of Wuhe complex generally experienced the phase change of high pressure amphibolite, and its temperature range is T = 671 ℃ ~ 700 ℃ and P = 0.82 ~ 0.95GPa, and the geothermal gradient is about 25 ~ 28 ℃ / km, similar to the typical geothermal gradient of continental crust. Compared with the metamorphism level of the main rock units in the adjacent area, the Wuhe complex should be formed in a metamorphic environment inside the plate and does not possess metamorphic characteristics of the orogenic belt.