Hydrochemistry Characteristics and Origin of New Brine Sandy Gravel inEarly Pleistocene of Heibei Concave in Qaidam Basin
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摘要: 柴达木黑北凹地深部砂砾石层内的承压水是近期在柴达木西部新发现的规模巨大的孔隙卤水,水位埋深8~24 m,接近地表;富水性中等偏强;矿化度较高,KCl含量达到可开发利用的要求,井采时不易结盐,可作为后续开发钾盐的备选区域.离子统计分析结果显示,TDS、Cl-、Na+、Cs+、B2O3、Ca2+、Mg2+、Sr+、NO3-、Rb+在卤水中的浓度变化幅度小,分布较均匀;SO42-的变化幅度大,分布极不均匀;Br-、I-、Li+、K+变化幅度和均匀程度介于二者之间;Na+、Cl-、Ca2+、Sr2+、TDS呈正态负偏高峰态,K+、SO42-、Li+呈非正态正偏高峰态.成分聚类分析图中,K+、SO42-、Li+首先聚为一亚类,Cl-、TDS、Na+聚为一亚类.从离子含量变化曲线图中可以看到,该孔隙卤水从东至西,Na+、Cl-含量和变化趋势相同,且它们与TDS、B2O3的变化趋势相同.K+、SO42-、Mg2+三种组分含量较一致,变化趋势相同,且同时与Li+的变化趋势相同.孔隙卤水钠氯系数CNa/CCl值为0.85~0.96,溴氯系数为0.01~0.34,与盐岩溶滤卤水接近.在Na+、K+、Mg2+//Cl--H2O四元体系和Na+、K+、Mg2+//Cl-、SO42--H2O五元体系25 ℃介稳相图中反映出2种析盐规律,一种为硫酸镁亚型,另一种是氯化物型.其形成可能与化学沉积层中高矿化度晶间卤水与砂砾石层中原始孔隙(淡)水相互作用有关.Abstract: Confined water in deep sandy gravel layer is newly-discovered large-scale pore brines in Heibei concave in the western Qaidam basin, which poses as an alternative area for potash development due to the following features: medium to strong water yield property, closeness to the surface with water level ranging from 8 to 24 m, high degree of mineralization, high KCl content fit for commercial development, and small salt buildup when mined. The statistical results show that concentration changes of TDS, Cl-, Na+, Cs+, B2O3, Ca2+, Mg2+, Sr+, NO3-, and Rb+ in the brine are small with even distribution. On the contrary, concentration changes of SO42- are big with uneven distribution; concentration changes of Br-, I-, Li+, K+ and uniform degree fall in the range in-between those of the two above-mentioned groups of elements; Na+, Cl-, Ca2+ and Sr2+, TDS show normal negatively skewed peak distribution, K+, SO42-, Li+ show non-normal positively skewed peak distribution. In component clustering analysis diagram, K+, SO42-, Li+ fall into a sub-class, whereas Cl-, TDS and Na+ fall into another sub-class The ion content change curve shows that content of Na+ and Cl- share the same change trend with that of mineralization degree and B2O3 in the pore brine from east to west. Compositions of K+, SO42-, Mg2+ are consistent, with the same change trend with that of Li+. Ratio of CNa/CCl in pore brine is 0.85-0.96, and bromine chloride coefficient is 0.01-0.34, similar to those of salt karst filter brine. It finds two laws of salting, namely, magnesium sulfate and chloride in the metastable phase diagram (25 ℃) of the quaternary system of Na+, K+, Mg2+//Cl--H2O and quinary system of Na+, K+, Mg2+//Cl-, SO42--H2O, which might have formed due to interaction of intercrystalline brine in the sedimentary formation and pore water in the sandy gravel.
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Key words:
- Heibei concave /
- brine /
- hydrochemical composition /
- hydrochemical type /
- metastable phase diagram /
- sand and gravel
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图 1 柴达木西部第四纪早更新世孔隙卤水储层分布
1.第四纪早更新世阿拉尔组; 2.新近纪上新世狮子沟组; 3.新近纪上新世上油砂山组; 4.前新近纪; 5.山前冲洪积扇(靠近山前为砂砾石建造, 向盆地内为细碎建造); 6.盐湖内带; 7.盐湖外带; 8.干盐湖; 9.地质界线; 10.角度不整合地质界线; 11.断层; 12.砂砾石层等厚度线; 13.古水流方向; 14.钻孔位置及编号; 15.图 2位置; 16.研究区
Fig. 1. Early pleistocene of quaternary pore brine reservoir distribution map in western Qaidam
表 1 调查区地层分层
Table 1. The survey area stratum
岩组(段、层)划分 代号 岩性 沉积环境 卤水类型 全新统达布逊组 Qh 化学沉积层 现代盐湖相沉积 晶间卤水 上更新统察尔汗组 Qp3 化学沉积层夹粘土层 干盐湖相、泥坪相 晶间卤水 中更新统尕斯库勒组 Qp2 化学沉积层与粘土层互层 干盐湖相、泥坪相 晶间卤水 上岩段 Qp13 粘土层夹厚层石盐层 泥坪相、干盐湖相 晶间卤水 中岩段 Qp12 粘土层夹薄层石盐层 泥坪相、局部干盐湖相 晶间卤水 下更新统阿拉尔组 下 上层 Qp1 Qp11-3 含石膏的粘土层夹砂砾石层 西部晶间 岩 中层 Qp11 Qp11-2 砂砾石层夹粘土层 西部干盐湖相、东部冲洪积相 卤水,东部 段 下层 Qp11-1 砂砾石层,局部夹粘土层 孔隙卤水 表 2 研究区向斜凹地钻孔多项分析离子平均含量
Table 2. Drilling multiple analysis of average ion content of syncline concave ground in the research area
样号 凹地砾砂层 凹地化学沉积层 南翼山背斜构造 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 K+(g/L) 1.88 1.19 1.99 3.41 3.32 3.24 3.29 1.16 1.10 1.00 0.81 2.62 2.61 2.52 2.61 2.62 2.52 2.32 6.81 Na+(g/L) 80.40 43.00 96.00 102.30 101.80 102.60 103.40 114.50 114.10 114.70 114.90 97.55 96.89 94.04 96.29 96.92 96.08 102.80 86.32 Ca2+(g/L) 4.61 2.43 5.06 5.42 5.52 5.50 5.43 3.53 3.50 3.58 3.51 5.67 5.54 5.38 5.53 5.54 5.46 4.94 15.57 Mg2+(g/L) 4.54 2.44 4.81 5.62 5.54 5.47 5.53 1.81 1.77 1.68 1.55 5.97 5.82 5.61 5.91 5.89 5.76 4.58 1.32 Li+(mg/L) 2.47 1.75 2.96 1.53 1.54 1.53 1.49 1.03 0.95 0.91 0.74 2.41 2.33 2.35 2.38 2.36 2.35 1.79 2.50 Rb+(mg/L) 0.18 0.15 0.19 0.10 0.09 0.09 0.08 <0.01 <0.01 <0.01 <0.01 <0.10 <0.10 <0.10 <0.10 <0.10 <0.10 0.11 - Cs+(mg/L) 0.96 0.60 1.14 0.53 0.52 0.51 0.53 1.01 1.04 1.03 1.06 <0.10 <0.10 <0.10 <0.10 <0.10 <0.10 0.82 - Sr2+(mg/L) 50.12 29.21 59.18 45.49 45.92 50.23 51.55 63.03 64.00 62.92 62.92 82.02 78.92 72.84 77.55 81.98 74.38 64.86 - Cl-(g/L) 144.20 75.21 170.10 183.60 184.60 184.60 185.70 184.90 186.70 187.70 187.70 177.70 176.70 170.70 175.70 175.20 175.20 180.45 171.06 SO42-(g/L) 1.47 1.78 1.51 1.61 1.43 1.47 1.52 1.96 2.14 1.94 2.01 1.38 1.28 1.27 1.10 1.28 1.27 1.54 263.33 CO32-(mg/L) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 19.45 HCO3-(mg/L) 55.01 188.20 6.76 13.05 13.05 13.05 19.58 19.53 37.32 27.95 31.68 0.00 0.00 0.00 0.00 0.00 0.00 12.13 246.24 B2O3(mg/L) 117.20 58.59 151.60 59.57 55.85 63.30 55.85 72.16 69.49 69.49 69.49 142.40 138.20 138.20 138.20 146.70 140.30 100.72 - Br-(mg/L) 1.76 1.98 0.68 52.40 46.80 53.20 47.20 54.40 54.40 52.80 56.00 59.67 59.17 57.50 57.17 54.33 54.67 19.63 52.10 I-(mg/L) 0.00 0.37 0.00 - - - - 7.90 7.65 7.90 7.60 5.45 5.90 5.65 5.80 5.85 6.05 1.37 36.44 NO3-(mg/L) 21.00 20.00 28.80 41.60 40.80 42.40 42.40 39.00 34.50 34.50 57.00 16.00 15.40 15.00 15.60 15.60 14.40 82.32 - 密度(g/cm3) 1.16 1.09 1.18 1.20 1.20 1.20 1.20 1.20 1.19 1.19 1.20 1.18 1.18 1.17 1.18 1.18 1.17 1.72 1.19 pH 7.39 7.70 7.40 7.70 7.75 7.70 7.76 7.48 7.50 7.49 7.51 7.52 7.14 7.47 7.24 7.17 7.47 13.19 - 矿化度(TDS)(g/L) 237.27 126.29 279.63 301.9 302.20 302.80 304.80 308.00 309.50 310.80 310.70 291.30 289.20 279.90 287.50 287.90 286.70 340.43 285.39 CNa/CCl 0.86 0.88 0.87 0.86 0.85 0.86 0.86 0.96 0.94 0.94 0.94 0.85 0.85 0.85 0.85 0.85 0.85 0.92 0.78 [K+]×1 000/[Cl-] 10.00 20.00 10.00 20.00 20.00 20.00 20.00 10.00 10.00 10.00 0.00 10.00 10.00 10.00 10.00 10.00 10.00 50.00 40.00 100×[SO42+]/2[Cl-] 0.51 1.18 0.44 0.44 0.39 0.40 0.41 0.53 0.57 0.52 0.54 0.39 0.36 0.37 0.31 0.37 0.36 10.67 0.08 [Ca2+]/[Mg2+] 1.02 1.00 1.05 0.96 0.99 1.01 0.98 1.95 1.98 2.12 2.27 0.95 0.95 0.96 0.94 0.94 0.95 0.02 11.86 [Ca2+]/[Mg2+] 0.01 0.03 0.00 0.29 0.25 0.29 0.25 0.29 0.29 0.28 0.3 0.34 0.33 0.34 0.33 0.31 0.31 0.10 0.31 [K+]/[Br-]×1 000 1.07 0.60 2.93 0.07 0.07 0.06 0.07 0.02 0.02 0.02 0.01 0.04 0.04 0.04 0.05 0.05 0.05 2.23 0.13 水化学类型 氯化物型 硫酸镁亚型 氯化钙型 备注 孔隙卤水 晶间卤水 构造裂隙水 注:1.梁ZK03SD01;2.梁ZK03SD02;3.梁ZK03SD03;4.梁ZK05SD01;5.梁ZK05SD02;6.梁ZK05SD03;7.梁ZK05SD04;8.梁ZK07SD03;9.梁ZK07SD04;10.梁ZK07SD05;11.梁ZK07SD06;12.黑ZK02I SD01;13.黑ZK02ISD02;14.黑ZK02IISD02;15.黑ZK02ISQ01;16.黑ZK02ISQ02;17.黑ZK02IISQ01;梁ZK03SD01、梁ZK03SD02、梁ZK03SD03;采样位置304.2~501.5 m,梁ZK05SD01、梁ZK05SD02、梁ZK05SD03、梁ZK05SD04;采样位置331~1 025 m,梁ZK07SD06、梁ZK07SD04、梁ZK07SD05、梁ZK07SD03;采样位置465.5~1 029.6 m,黑ZK02ISD01、黑ZK02IISD02、黑ZK02ISQ01、黑ZK02IISQ01、黑ZK02ISQ02、黑ZK02ISD02;采样位置381.05~808.46 m. 表 3 研究区孔隙卤水分布特征
Table 3. Pore brine distribution list in the research area
成分 Cv Cs Ce 特征 K+ 0.88 2.37 5.42 非正态正偏高峰态 Na+ 0.16 -2.39 7.77 正态负偏高峰态 Ca2+ 0.41 -1.50 1.46 正态负偏高峰态 Mg2+ 0.42 -0.40 -0.42 正态负偏低峰态 Cl- 0.15 -3.44 12.88 正态负偏高峰态 SO42- 1.99 2.88 7.24 非正态正偏高峰态 Li+ 0.79 2.33 5.37 非正态正偏高峰态 B2O3 0.39 0.33 -1.87 正态正偏低峰态 Rb+ 0.50 0.87 -0.05 正态正偏低峰态 Cs+ 0.37 0.18 -2.13 正态正偏低峰态 Sr2+ 0.43 -1.24 1.23 正态负偏高峰态 Br- 0.56 -1.12 -0.69 非正态负偏低峰态 I- 0.70 -0.55 -1.54 非正态正偏低峰态 NO3- 0.44 0.44 -0.71 正态正偏低峰态 密度 0.02 -2.17 7.15 正态负偏高峰态 pH值 0.02 -0.53 -0.25 正态负偏低峰态 矿化度(TDS) 0.16 -2.88 10.20 正态负偏高峰态 注:Cl-<Na+=TDS<Cs+<B2O3<Ca2+<Mg2+<Sr+<NO3-<Rb+:<Br-<I-<Li+<K+:<SO42-. 表 4 K+、Na+、Mg2+//Cl--H2O(25 ℃)介稳相图指数
Table 4. K+, Na+, Mg2+//Cl--H2O 25 ℃ of interface stability phase diagram index
图点号 样品编号 水化学组分(%) 相图指数(%) KCl NaCl MgCl2 KCl NaCl MgCl 1 梁ZK03D01 0.31 17.36 1.53 1.588 90.531 7.881 2 梁ZK03D02 0.21 9.7 0.88 1.873 90.248 7.878 3 梁ZK03D03 0.32 20.45 1.60 1.423 91.509 7.068 4 梁ZK05D01 0.54 21.39 1.83 2.254 90.118 7.628 5 梁ZK05D02 0.53 21.53 1.81 2.208 90.222 7.570 6 梁ZK05D03 0.51 21.57 1.79 2.142 90.426 7.432 7 梁ZK05D04 0.52 21.72 1.80 2.155 90.395 7.450 8 梁ZK07D03 0.18 23.88 0.59 0.733 96.907 2.359 9 梁ZK07D04 0.18 24.37 0.58 0.703 96.985 2.312 10 梁ZK07D05 0.16 24.5 0.55 0.637 97.165 2.198 11 梁ZK07D06 0.13 24.34 0.51 0.517 97.457 2.026 12 黑ZK02S(I)Q01 0.42 20.55 1.96 1.824 89.698 8.478 13 黑ZK02S(II)D01 0.42 20.80 1.98 1.808 89.726 8.466 14 黑ZK02S(II)D02 0.41 20.21 1.88 1.807 89.923 8.269 表 5 研究区K+、Na+、Mg2+//Cl--H2O(25 ℃)度介稳相图指数
Table 5. K+, Na+, Mg2+//Cl--H2O (25 ℃) of interface stability phase diagram index table in the research area
图点号 样品编号 离子含量(g/L) 相图指数(%) K+ Mg2+ SO42- 2K+ Mg2+ SO42- 1 梁ZK01D05 9.44 8.73 26.47 15.98 47.55 36.47 2 梁ZK01D011 11.40 7.26 33.34 18.42 37.74 43.85 -
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