Formation of fault bend fold-controlled meteoric karst reservoir in the middle and late Himalayan movement: A case study of the Dawangou Formation carbonate rocks at Yangjikan section, Keping, northwestern Tarim Basin

Qian Yixiong; Tian Mi; Li Huili; Chen Yue; Sha Xuguang; Li Hongquan

doi:10.11743/ogg20190405

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Formation of fault bend fold-controlled meteoric karst reservoir in the middle and late Himalayan movement: A case study of the Dawangou Formation carbonate rocks at Yangjikan section, Keping, northwestern Tarim Basin
Vol. 40, Issue 4, Pages: 738-751(2019)
Online First：28 August 2019，

Published：2019
DOI： 10.11743/ogg20190405
稿件说明：

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DOI：

Qian Yixiong, Tian Mi, Li Huili, et al. Formation of fault bend fold-controlled meteoric karst reservoir in the middle and late Himalayan movement: A case study of the Dawangou Formation carbonate rocks at Yangjikan section, Keping, northwestern Tarim Basin[J]. 2019, 40(4): 738-751. DOI： 10.11743/ogg20190405.

摘要

在新疆柯坪羊吉坎中奥陶统大湾沟组碳酸盐岩岩溶特征刻画的基础上，采用了岩相学、地球化学以及褶皱脱空分析等综合研究，并结合了古气候分析等溶蚀实验结果，揭示了喜马拉雅中晚期受断弯褶皱抬升及大气水溶蚀控制岩溶作用过程；估算了受构造挤压的层间滑脱以及溶蚀作用所产生孔隙大小。褶皱脱空（VSD模拟计算）可产生0.2%~0.5%孔隙发育带，占目前有效空洞率的1/50~1/100，但前者为“达西流及溶蚀作用”起了重要的作用。羊吉坎岩溶剖面中发育了机械破碎-流水充填物（角砾岩）、钙华及巨晶方解石；与大湾沟组的围岩相比，其δ

C（PDB），δ

O（PDB）偏负明显、两者呈线性关系，缝洞中方解石中发育了单相盐水溶液包裹体，典型的大气水岩溶标志；由下而上连续钙华沉积δ

C（PDB），δ

O（PDB），δ

S（V-CDT）偏负的程度减弱；从钙华、巨粗晶至（长）柱面的偏三角面体的方解石中，Al

，Fe

，MgO，K

O，Na

O含量依次降低；反映了半潮湿-潮湿至半潮湿-干旱气候条件及其水动力的变化。进一步推断，在潮湿气候和强水动力条件下，高1.5~2.0 m的溶洞体最短可在5 ka内形成，而相对干旱期需要较长的时间。

Abstract

The karst profile at Yangjikan section

Keping

northwestern Tarim Basin

provides an excellent opportunity to evaluate the relative importance of reaction between fault bend fold-controlled uplift and meteoric water dissolution-controlled karstification during the middle and late Himalayan movement; and then the porosity caused by interlayer decollement under structural compression and dissolution was estimated

in line with the comprehensive study of petrographic

geochemical and fold disengaging analyses.The fold disengaging(simulated with VSD)facilitated the result of 0.2%-0.5% porous zones

accounting for 1/50-1/100 of the effective and actual empty-cavity rate.However

the porous zones have played a significant role in Darcy flow channel formation and karstification.The breccias related to mechanical fracture filling

calcareous tufas and megacrystalline calcites are well developed in the Yangjikan section karst reservoir.Compared to the surrounding rocks of the Dawangou Formation

the negative and linear correlation of δ

O(PDB)and δ

C(PDB)in the formation is distinct

and single-phase aqueous inclusions

typical products of meteoric water karstification

grew in the megacryst calcites within fractures and cavities.A successive tufa depositions from the lower to the upper section of karst profile

are characteristic of weakening negative depleted δ

O(PDB)

O(PDB) and δ

S(V-CDT).The content of Al

MgO

and Na