伊犁盆地西南缘侏罗系沉积旋回划分及其与铀成矿的关系
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摘要
根据岩性在垂向上的变化特征,结合煤层的发育情况,伊犁盆地西南缘侏罗系划分为8个沉积旋回。该划分方案主要以地层中比较稳定的煤层做为一个旋回结束的标志,但是在煤层不发育的部位,或者研究区以外的盆地其他地区,在地层划分和对比过程中就会出现人为的不确定性。本文运用旋回地层学理论,利用能敏感地反映岩性尤其是泥、砂含量变化,有效记录地层序列中沉积旋回和沉积环境特点的自然伽马测井曲线,采用累积残差、滤波处理等方法,正弦波拟合等手段,在研究区侏罗系地层识别出了6个完整的向上变细—向上变粗的沉积旋回,以及1个向上变细的正旋回。划分出的沉积旋回在区域内稳定出现,且不受煤层等其他标志层出现或缺失的影响。在侏罗系地层中旋回厚度最大的分布在西山窑组上段,最小的地层分布在三工河组。但是旋回厚度变化最独特的是西山窑组下段,旋回厚度呈阶梯式逐渐增大,而西山窑组下段就是伊犁盆地铀成矿潜力最大的地层。旋回厚度的变化对应沉积速率的变化,由此可以推测沉积速率成阶梯状、逐渐增大的层位,应该是以后找矿工作中的重要目的层。
According to the vertical change characteristics of lithology and the development of coal seam, the Jurassic strata in the southwest margin of Yili basin are divided into 8 sedimentary cycles. The classification scheme marks an end to a cycle just in relatively stable bearing-coal strata,but not in the coal-developing areas,or other areas outside the study area of the basin,the stratigraphic division and correlation in the process will appear artificial uncertainty. Studying sedimentary cycle and deposition rate of Jurassic in the southwestern margin of yili basin,summarizing it's relationship to uranium deposit. Using cyclic stratigraphy theory,cumulative residuals,filter processing methods,sine wave fitting method,in recognition of the Jurassic formations in the study area out of the 6 complete upward fining-toward the table thick sedimentary cycles,and 1 upward fining positive cycle. Sedimentary cycle division of the stability in the region,and is not affected by the presence or absence of coal and other marker bed. In the Jurassic strata,the maximum thickness of the cycle is distributed in Upper Xishanyao Formation,and the smallest is distributed in the Sangonghe Formation. However,the most unique change of cycle thickness is the Lower Xishanyao Formation,the cyclic thickness increases gradually,while the Lower Xishanyao Formation is the largest metallogenic potential of Uranium deposits in Yili basin. The change of cycle thickness corresponds to the change of sedimentary rate,so it can be inferred that the sedimentary rate of a layer is gradually increasing,which should be an important target layer for future prospecting work.
According to the vertical change characteristics of lithology and the development of coal seam, the Jurassic strata in the southwest margin of Yili basin are divided into 8 sedimentary cycles. The classification scheme marks an end to a cycle just in relatively stable bearing-coal strata,but not in the coal-developing areas,or other areas outside the study area of the basin,the stratigraphic division and correlation in the process will appear artificial uncertainty. Studying sedimentary cycle and deposition rate of Jurassic in the southwestern margin of yili basin,summarizing it's relationship to uranium deposit. Using cyclic stratigraphy theory,cumulative residuals,filter processing methods,sine wave fitting method,in recognition of the Jurassic formations in the study area out of the 6 complete upward fining-toward the table thick sedimentary cycles,and 1 upward fining positive cycle. Sedimentary cycle division of the stability in the region,and is not affected by the presence or absence of coal and other marker bed. In the Jurassic strata,the maximum thickness of the cycle is distributed in Upper Xishanyao Formation,and the smallest is distributed in the Sangonghe Formation. However,the most unique change of cycle thickness is the Lower Xishanyao Formation,the cyclic thickness increases gradually,while the Lower Xishanyao Formation is the largest metallogenic potential of Uranium deposits in Yili basin. The change of cycle thickness corresponds to the change of sedimentary rate,so it can be inferred that the sedimentary rate of a layer is gradually increasing,which should be an important target layer for future prospecting work.
引文
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[16]李江涛,李增学,余继峰,等.基于测井数据小波变换的层序地层对比--以鲁西和济阳地区石炭、二叠系含煤地层为例[J].沉积学报,2005,23(4):639-645.
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[18]刘洋,吴怀春,张世红,等.珠江口盆地珠一坳陷韩江组-万山组旋回地层学[J].地球科学--中国地质大学学报,2012,37(3):411~423.
[19]Harper D A T,Ryan P D.Towards a statistical system for palaeontologists[J].Journal of the Geological Society,1990,147:935~948.
[20]黄冰,David A T Harper.定量古生物学软件PAST及其常用功能[J].古生物学报,2013,52(2):161~181.
[2]侯惠群,韩绍阳,柯丹.新疆伊犁盆地南缘砂岩型铀成矿潜力综合评价[J].地质通报,2010,29(10):1517~1525.
[3]赵瑞全,秦明宽.微生物和有机质在512层间氧化带砂岩型铀矿成矿中的应用[J],铀矿地质,1998 14(3):338~343.
[4]张卫民,刘金辉,孙占学,等水岩体系Eh-pH法及其在砂岩型铀矿体定位研究中的应用--以新疆伊犁盆地512铀矿床为例[J]华东地质学院学报2002,25(3):9l~96.
[5]李盛富.流水地貌与铀矿床的关系[J].铀矿地质,2003,19(4):232-236.
[6]刘章月,秦明宽,刘红旭,等.新疆蒙其古尔铀矿床高岭石氢氧同位素组成及其指示意义[J].铀矿地质,2015,31(S1),225~231.
[7]黄世杰.层间氧化带型铀矿形成条件及找矿判据[J],铀矿地质,1994.10(1):6~13.
[8]李盛富,颜启明,王新宇,等.伊犁盆地水西沟群冲积扇-扇三角洲沉积体系研究[J].新疆地质,2006,24(3):297~304.
[9]李盛富,陈洪德,周剑,等.沉积盆地源-汇过程演化对砂岩型铀成矿的制约--以新疆伊犁盆地南缘蒙其古尔铀矿床为例[J].铀矿地质,2016,32(3):137~145
[10]陈戴生,李胜祥.伊犁盆地层间氧化带砂岩型铀矿成矿模式[J],铀矿地质,1997.13(6):327~335.
[11]李盛富,张蕴.砂岩型铀矿床中铀矿物的形成机理[J].铀矿地质,2004,20(2):80~84.
[12]蒋宏,王芳霞,方敏.伊犁盆地南缘蒙其古尔铀矿床含矿砂体与铀成矿的关系[J].铀矿地质,2015,31(S1),213~218.
[13]伊海生.测井曲线旋回分析在碳酸盐岩层序地层研究中的应用[J].古地理学报,2011,13(4):456~466.
[14]伊海生.地层记录中旋回层序界面的识别方法及原理[J].沉积学报,2012,30(6):991~998.
[15]梁定勇,伊海生,邱余波,等.松辽盆地东岭地区泉头组高频沉积旋回的叠加型式分析[J].沉积学报,2014,32(2):198~204.
[16]李江涛,李增学,余继峰,等.基于测井数据小波变换的层序地层对比--以鲁西和济阳地区石炭、二叠系含煤地层为例[J].沉积学报,2005,23(4):639-645.
[17]邱余波,伊海生,张军,等.新疆鄯善油田S3砂层组高频旋回的识别与划分[J].科技导报,2011,29(24):51~56.
[18]刘洋,吴怀春,张世红,等.珠江口盆地珠一坳陷韩江组-万山组旋回地层学[J].地球科学--中国地质大学学报,2012,37(3):411~423.
[19]Harper D A T,Ryan P D.Towards a statistical system for palaeontologists[J].Journal of the Geological Society,1990,147:935~948.
[20]黄冰,David A T Harper.定量古生物学软件PAST及其常用功能[J].古生物学报,2013,52(2):161~181.
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