摘要
桂西南地区锰矿床资源富集并具有较好的找矿前景,然而目前有关该区三叠系主要沉积地层的地层格架划分尚较薄弱且鲜有探讨。利用桂西南地区东平锰矿区四口钻孔的自然伽马测井曲线进行去趋势、高通滤波处理以及累计残差计算等方法,对桂西南地区含锰岩系进行了旋回地层学研究。研究结果表明:含锰岩系下三叠统北泗组共可划分为四个海进—海退旋回层序,碳酸锰矿层发育的旋回层序位置主要出现于各旋回层序内海退沉积序列中,并位于旋回层序内海退—海侵界面附近,锰矿沉积主要发生在相对海平面由缓慢下降至逐渐上升的时期的转换时期。综合研究区锰矿形成的海平面变化、古地理条件、锰质来源、氧化还原条件等特征的基础上,笔者提出了研究区锰矿成因模式,即具有地理隔绝形式的、并由同生断裂控制的"局限海"台盆相碳酸锰矿沉积模式,碳酸锰矿的形成主要经历以下3个阶段:1)海平面下降—氧化锰矿物形成阶段;2)海平面上升—氧化锰矿物转化碳酸锰矿物阶段;3)最高海泛面—少量碳酸锰矿物发育阶段。该研究成果可为桂西南地区今后锰矿勘探工作中的地层分析、建立区域内高频层序单元格架及锰矿成因等研究提供一种新的方法和手段。
The manganese deposits are mainly distributed in Southwestern Guangxi area,which was regarded as one of the most predominant ore types in this area. However,the Triassic stratigraphic frameworks of manganese deposit in the southwestern Guangxi area is rarely discussed. The spectral analysis and filter methods can be adopted to divide cyclic sequence hierarchy and discuss depositional mechanism,and the cumulative residual curves from average amplitude variations of good logs are introduced and demonstrated as a valid graphical method to define depositional regime transformation and check boundary surfaces of cyclic sequences. The cumulative residual curves results show the positive half waves and negative half waves of cumulative residual curves are,respectively,corresponds to upwarddeepening and upward-shallowing sedimentary successions in low frequency cyclic sequences in a well interval. Transform points of positive half waves and negative half waves are calibrated to boundary surface depth of cyclic sequences.The GR log data from Well 0302 of Southwestern Guangxi Area as a case example,cumulative residual curves are calculated and constructed on well log data. The low and high frequency cyclic sequences are distinguished and its procedure and methods are illustrated in detail. The significance and interpretation of amplitudes and wavelength changes of sedimentary cycles are discussed in this paper. The Beisi Formation of the Lower Triassic can be divided into four forth-order sequences,and the manganese ore deposit developed in the regression cycle. The origin model of manganese ore can be divided in three stages： 1） Sea-level fall-the oxidizing manganese is formation; 2） Sea-level rise-the oxidizing manganese is transformed in manganese carbonate; 3） The maximum flooding surface-a little manganese carbonate is formed. The investigation provides a new effective approach to build the correlating framework of high-resolution sequence in Southwestern Guangxi Area.
出处
《沉积学报》
CAS
CSCD
北大核心
2017年第6期1144-1157,共14页
Acta Sedimentologica Sinica
基金
"十二五"国家科技支撑计划项目(2011BAB04B10)
国家自然科学基金项目(40972084)
高等学校博士点专项科研基金课题(20105122110012)~~
关键词
桂西南地区
三叠系
含锰岩系
旋回地层
海平面变化
Technology
spectral analysis
cumulative residual curves
cyclic sequences
oxidizing manganese
