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前寒武纪张八岭建造是一套海底喷发的火山岩系,其原岩由大量石英角斑岩和少数细碧岩及其火山碎屑岩、凝灰质沉积岩组成,并与海相的硅质岩、白云质石灰岩透镜体、粉砂岩、页岩等伴生。受区域变质作用影响,形成绿片岩相的矿物组合。岩石具典型的熔岩组构。主要矿物成分为:石英、低温完全有序的钠长石(An<5)和绿泥石、绿帘石、磁铁矿等。岩石有明显的交代观象,其交代顺序为:钠化→钠硅化→钾化→硅化。据玻璃质固化包裹体测温,其岩浆温度为1030—1180℃;液相包裹体测温,其热液蚀雯温度为300℃。由岩石化学分析资料说明:变质火山岩为弱碱质钠质细碧岩——石英角斑岩系。两者为同源岩浆岩。其原始岩浆成分为——中酸性岩浆。经分异作用,主要向酸性岩浆转化;少量向基性。在岩浆结晶分异的同时并遭受海水及海相沉积物中钠质的混染,成为富钠质的岩浆,逐渐演变成富钠的透岩浆溶液,发生钠质交代,这种作用继续延到岩浆期后的热液期。其后岩石又经低级区域变质作用,形成石英角斑岩及细碧岩。根据变质火山岩的岩石学、岩石化学及火山岩中伴生岩石特征等地质因素,说明:它形成于浅海环境,靠大陆边沿,或岛弧。它是以酸性火山岩为主的,细碧岩——石英角斑岩系,与产于优地槽(或大洋扩张部位)发展早期的蛇绿岩套;包括基性、超基性岩。硅质岩及以基性组分为主的细碧岩——角斑岩建造是迥然不同的。它与岛弧晚期阶段的陆相安山岩——流纹岩也有一定的差别,可能是岛弧早期的产物。
The Precambrian Zhangbaling is a set of submarine eruptive volcanic rocks. Its original rock is composed of a large number of quartz horn porphyries and a few small bixites and their pyroclastic rocks and tuffaceous sedimentary rocks, which are connected with the marine chert, Dolomitic limestone lens, siltstone, shale and other associated. Affected by the regional metamorphism, the formation of the green schist facies mineral assemblage. Rock with a typical lava fabric. The main mineral components are: quartz, fully ordered low temperature albite (An <5) and chlorite, epidote, magnetite and so on. The rock has a clear account of the image, the order of interpretation: sodium → sodium silicosis → potassium → silicification. According to glassy solidified inclusions temperature, the magma temperature is 1030-1180 ℃; liquid inclusions temperature, the hydrothermal etching temperature of 300 ℃. The petrochemical analysis shows that the metamorphic volcanic rocks are weakly alkaline sodium pyroxene-quartz horn porphyry. Both are the same magmatic rocks. The original magmatic component is - acid magma. The differentiation effect, mainly to acidic magmatic transformation; a small amount of basic. At the same time as the differentiation of the magma crystals and suffered from seawater and marine sediment sodium contamination, become rich in sodium magma, and gradually evolved into sodium-rich solution through the exchange of sodium, the sodium continued to explain this role continues to extend to the magma Period after the hydrothermal period. Later, the rocks were further metamorphosed by low-grade regions to form quartz horn porphyry and small bijinite. According to the geology of metamorphic volcanic rocks, petrochemistry and associated rock characteristics in volcanic rocks, it shows that it is formed in the shallow sea environment by the continental margin or island arc. It is mainly composed of acidic volcanic rocks, small bi-quartz-quartz porphyry and ophiolite sets developed in the early stage (or oceanic expansion), including basic and ultrabasic rocks. Silicalites and basic components of the main bixite - angular porphyry construction is very different. It is also different from the continental andesite-rhyolite in the late stage of the island arc and may be the product of the island arc early.