塘古坳陷YL6井寒武系盐下变质岩地层厘定及地质意义

塔里木盆地台盆区广泛发育下寒武统白云岩，厚度大、生储盖条件优越使其具有广阔的勘探前景，而YL6井在中寒武统膏盐岩之下钻揭了一套巨厚大理岩，这对于早寒武世玛东构造带是否为正常沉积的台盆相碳酸盐岩提出了质疑。通过岩心、岩屑薄片、扫描电镜资料明确了塘古坳陷YL6井巨厚大理岩的岩石学特征，根据大理岩变质特征、特征变质矿物的分布以及海绵骨针的发现，结合地震、测井等资料进一步明确了YL6井大理岩的母岩时代及变质成因。研究表明:(1)YL6井大理岩表现为过渡变质特征，大理岩中的特征变质矿物和酸性热液相关矿物证明其为晚期酸性热液活动的变质产物，并非区域变质基底；(2)大理岩中古生物化石以及地震、沉积背景资料表明玛东地区广泛分布正常沉积的下寒武统白云岩，局部因断裂沟通热源导致变质；(3)玛东构造带寒武系盐下石油地质条件优越，具有寻找盐下原生构造油气藏以及岩性—构造复合油气藏的勘探潜力。

Stratigraphy of the Cambrian Subsalt Metamorphic Rocks in the Tanggu Depression (Well YL6) and Its Petroleum Geological Significance

Thick layers of Cambrian dolomite with favorable petroleum geological conditions and great exploration potential are widely developed in the inter platform basin of the Tarim Basin. However, the rocks under middle Cambrian in well YL6 are marble instead of dolomite, and their age determines whether the paleo land extended to the Madong tectonic belt in the Early Cambrian. By analyzing the drill cores, slices, SEM data, fossils, logging and seismic data, we identified the petrological characteristics and formation of the marble in well YL6. We concluded that: (1) Distribution of the marble in well YL6 is transitional, and the metamorphic minerals in the marble indicate that the marble in well YL6 was formed by local thermal metamorphism instead of regional metamorphism; (2) Fossils and seismic data indicate that the Lower Cambrian dolomite is widely distributed in Madong area, and that the metamorphism occurred along deep faults which are locally distributed in this area;(3) The Lower Cambrian sequences in the Madong area have favorable petroleum geological conditions and exploration potential for discovering primary reservoirs and structural lithologic reservoirs.