摘要
从碳酸盐岩的岩石学、建造特征的分析入手,研究了区内石炭-二叠纪碳酸盐岩的沉积特征及其地质意义.野外调查表明,本区域石炭-二叠纪碳酸盐岩以砾屑灰岩、海百合灰岩和微晶灰岩为主,块状构造和粒序层理常见,作为碳酸盐岩建造底座及夹层的火山岩或火山碎屑岩发育,显示了本区域石炭-二叠纪期间张裂频繁、火山作用强烈、地形较陡和覆水较深的浅海古地理背景.本区域石炭-二叠纪碳酸盐岩建造发育于火山岩或火山碎屑岩、辫状三角洲或扇三角洲砂砾岩、海岸泥岩和陆架泥岩等底座之上,分别形成了火山抬高型(VEF)、三角洲垫高型(DEF)、海岸/隆起沉没型(CSF/USF)和陆架变浅型(SSF)4种碳酸盐岩建造.不同类型的碳酸盐岩建造,是区域构造和海平面升降联合作用的产物,但其形成机制有别,其中,火山垫高型建造最普遍,含火山岩或火山碎屑岩夹层,系区域海平面长期上升的背景下,构造张裂引发的火山喷发引起相对海平面下降的产物;三角洲垫高型建造分布也较广,含砂砾岩夹层,为区域海平面长期上升的背景下,构造抬升造成辫状三角洲或扇三角洲进积导致相对海平面下降形成;海岸/隆起淹没型和陆架变浅型建造为纯灰岩建造,相对较少,则是在区域构造稳定的构造背景下,短期相对海平面变化驱动的结果.然而,不同类型碳酸盐岩建造的沉积特征,则受沉积环境制约.同时,针对这4种不同的碳酸盐岩建造,分别建立了火山垫高型碳酸盐台地(VEP)、三角洲垫高型碳酸盐台地(DEP)、海岸/隆起淹没型碳酸盐缓坡(CSR/USR)和陆架变浅碳酸盐缓坡(SSR)4种沉积模式,不同的沉积模式形成了沉积特征有别的碳酸盐岩建造.该时期浅海陆棚的古地理背景,不仅为区内海相烃源岩的发育创造了良好的古地理条件,也使得这一时期的碳酸盐岩、底座火山岩或火山碎屑岩、辫状三角洲或扇三角洲砂砾岩,以及碳酸盐岩建造中的火山岩、火山碎屑岩和砂砾岩夹层,成为本区域石炭-二叠纪的潜在油气储层.
A study of depositional characteristics on carbonate rocks of Permo-Carboniferous was carried out by analyzing of petrology and their formation characteristics of carbonate rocks. A lot of fieldworks of the Permo-Carboniferous system in the study area indicate that,the carbonate rocks of Permo-Carboniferous are dominated by calcirudite,crinoidal limestone and micrite with massive structure and graded bedding,volcanic or pyroclastic rocks acting as pedestals and interbeds of the carbonate formations prevail in the area,which show the neritic paleoenvironmental settings of frequent tension-faulting,strong volcanism,steep topography and deeper water during the period of Permo-Carboniferous. The Permo-Carboniferous carbonate rock formations respectively on the pedestals of volcanic or pyroclastic rocks,granulites from braided river or fan deltas,mudstones originated from littoral zone and shelf comprise volcano-elevated carbonate rock formation (VEF),delta-elevated carbonate rock formation (DEF),coast-subsiding carbonate rock formation (CSF) and shelf-shoaling carbonate rock formation (SSF).The formations,all of which were formed by working together of region tectonics and change in sea level,show the distinct mechanism of construction. Among of them,the volcano-elevated formation,with volcanic or pyroclastic interbeds and prevailling in the area,originated from the relative sea level fall driven by volcano eruption resulting from tectonic extension,in the setting of long-term rise in sea level. The delta-elevated formation inferior to the volcano-elevated in development,with granulite interbeds,arose from the relative sea level fall driven by braided river or fan deltas progradation resulting from tectonic uplifting,in the context of long-term rise in sea level. The coast-subsiding and shelf-shoaling formations,subordinate to the former two,came from short-term sea level fall under the circumstances of regional steady tectonics. However,the depositional characteristics of the carbonate rock formations having the differences in lithology,depositional texture,depositional structure and paleo-fauna assemblage,are constrained by depositional environment. Besides,four kinds of deposition models for the four carbonate rock formations above,i.e. volcano-elevated carbonate platform (VEP),delta-elevated carbonate platform (DEP),coast/uplift-subsiding carbonate ramp (CSR) and shelf-shoaling carbonate ramp (SSR),are produced with distinct depositional characteristics respectively. The neritic shelf paleoenvironment of the age is favorable to development of the marine-originated source rocks. As a result of this,the carbonate rocks,the volcanic rocks,pyroclastic rocks,and the granulites of pedestals and interbeds,originated from braided river and fan deltas become the potential reservoirs of Permo-Carboniferous for oil and gas in the area.
出处
《地球科学(中国地质大学学报)》
EI
CAS
CSCD
北大核心
2011年第1期62-72,共11页
Earth Science-Journal of China University of Geosciences
基金
中国地质大调查项目(No.1212010733506)
关键词
碳酸盐岩
沉积特征
储层
海平面变化
石炭-二叠纪
石油地质
内蒙古
carbonate rocks
sedimentary characteristics
reservoirs
change in sea level
Permo-Carboniferous
petroleum geology
Inner Mongolia.