0 引言
1 区域地质概况
图1 四川盆地及邻区构造背景(a)与四川盆地须家河组残余厚度等值线图(b)及东北部构造简图(c)[(a)图据文献[30-31]修改,(b)图据文献[32]修改,(c)图据文献[33]修改,上三叠统古水流数据据文献[34-36]]Fig.1 The structural background map(a) of the Sichuan Basin and its adjacent areas, the isocontour map(b) of the residual thickness of Xujiahe Formation in the Sichuan Basin, and the structural sketch (c) in the northeast of the Sichuan Basin ((a) is modified from Refs.[30-31], (b) is modified from Ref.[32], (c) is modified from Ref.[33], Upper Triassic palaeocurrent data is from Refs.[34-36]) |
2 样品与分析
2.1 样品采集
表1 采集的野外露头样品信息Table 1 Information on field outcrop samples collected |
采集地 | 样品编号 | 层位 | 采样点坐标 | 岩性 |
---|---|---|---|---|
宣汉县七里乡 | Qlx-3 | T3 x 3 | N31°11.795′,E107°44.546′ | 深灰色泥岩 |
Qlx-5 | T3 x 5 | N31°11.849′,E107°44.258′ | 泥质粉砂岩 | |
Qlx-6 | T3 x 6 | N31°11.837′,E107°44.175′ | 灰色泥岩 | |
复平镇黑天池 | Htc-5 | T3 x 5 | N30°48.578′,E107°52.244′ | 泥质粉砂岩 |
天城镇铁峰山 | Tfs-2 | T3 x 2 | N30°55.383′,E108°20.588′ | 灰色砂岩 |
朱衣镇黄井水库 | Hjsk-2 | T3 x 2 | N31°03.368′,E109°15.476′ | 灰色泥岩 |
Hjsk-5 | T3 x 5 | N31°03.908′,E109°15.552′ | 黑色泥岩 | |
大巴山地质公园 | Dbs-3 | T3 x 3 | N31°39.256′,E108°15.488′ | 粉砂岩 |
万源市固军水库 | Gjsk-2 | T3 x 2 | N31°45.535′,E108°06.681′ | 灰色泥岩 |
长石镇黄家沟 | Hjg-4 | T3 x 4 | N32°04.8894′,E107°54.746′ | 灰色泥岩 |
2.2 分析测试
3 结果
3.1 岩石学特征
图2 野外露头典型地层剖面照片及岩性地层柱状图(a)大巴山地质公园剖面须二段球枕构造;(b)天城镇铁峰山剖面须二段灰白色中细砂岩和泥岩互层;(c)朱衣镇黄井水库须二段与下伏巴东组呈平行不整合;(d)宣汉县七里乡剖面须二段块状灰色砂岩夹泥砾和炭屑;(e)宣汉县七里乡剖面须三段暗色粉砂质泥页岩夹薄层砂岩;(f)宣汉县七里乡剖面须五段暗色炭质泥岩夹泥质粉砂岩;(g)大巴山地质公园剖面须六段中厚层砂岩;(h)复平镇黑天池剖面三叠系和侏罗系接触面侏罗系珍珠冲段介壳灰岩;(i)五宝浅15井单井沉积相柱状图 Fig.2 Typical outcrop profile photos and lithostratigraphic column charts |
图3 须家河组的成分分类和显微照片(a)须家河组Q—F—R三元图解;(b)五宝浅15井,2 663.19~2 663.32 m,T3 x 4,水下分流河道灰白色岩屑石英中砂岩;(c)五宝浅15井,T3 x 5,中粒岩屑砂岩(单偏光);(d)五宝浅15井,2 925.97 m,石英颗粒紧密接触(正交光);(e)万源市石冠寺野外露头,T3 x 2,石英—长石颗粒接触(正交光);(f)五宝浅15井,2 666.85 m,T3 x 4,千枚岩岩屑挤压变形(正交光);(g)大巴山地质公园野外露头,T3 x 2,方解石胶结(正交光);(h)五宝浅15井,2 922.55 m,T3 x 2,绿泥石薄膜和硅质胶结(正交光);(i)五宝浅15井,2 661.65 m,T3 x 4,伊利石胶结(正交光)。 Fig.3 Composition classification and micrograph of Xujiahe Formation |
3.2 元素地球化学特征
表2 须家河组样品主量、微量元素含量Table 2 Content of main elements and trace elements in samples from Xujiahe Formation |
Qlx-3 | Qlx-5 | Qlx-6 | Htc-5 | Tfs-2 | Hjsk-2 | Hjsk-5 | Dbs-3 | Gjsk-2 | Hjg-4 | ||
---|---|---|---|---|---|---|---|---|---|---|---|
主量 元素 /% | SiO2 | 48.07 | 55.50 | 60.33 | 53.02 | 69.65 | 55.02 | 51.06 | 59.23 | 55.75 | 56.50 |
Al2O3 | 11.35 | 17.51 | 17.75 | 13.32 | 14.02 | 17.11 | 15.68 | 17.55 | 16.58 | 18.86 | |
Fe2O3 | 6.49 | 9.15 | 6.99 | 7.92 | 4.06 | 10.02 | 7.56 | 9.16 | 10.36 | 8.40 | |
CaO | 9.87 | 3.24 | 3.19 | 6.36 | 3.16 | 3.48 | 5.31 | 3.25 | 3.65 | 3.17 | |
MgO | 2.67 | 2.15 | 1.96 | 2.36 | 1.02 | 2.34 | 3.41 | 1.90 | 2.48 | 1.83 | |
K2O | 2.90 | 3.38 | 2.65 | 2.99 | 3.49 | 3.35 | 3.79 | 2.41 | 3.87 | 2.77 | |
Na2O | 0.48 | 0.05 | 0.16 | 0.28 | 0.95 | 1.19 | 0.80 | 0.38 | 0.14 | 0.49 | |
MnO | 0.06 | 0.09 | 0.03 | 0.21 | 0.01 | 0.08 | 0.04 | 0.10 | 0.08 | 0.05 | |
TiO2 | 0.48 | 0.94 | 0.86 | 0.66 | 0.34 | 0.83 | 0.72 | 0.82 | 0.74 | 0.91 | |
P2O5 | 0.14 | 0.08 | 0.11 | 0.13 | 0.05 | 0.15 | 0.15 | 0.13 | 0.10 | 0.09 | |
Total | 82.52 | 92.07 | 94.02 | 87.23 | 96.74 | 93.56 | 88.52 | 94.92 | 93.76 | 93.07 | |
微量 元素 /10-6 | Ba | 238.31 | 562.77 | 557.68 | 390.50 | 316.17 | 503.35 | 363.53 | 522.87 | 447.38 | 625.22 |
Zr | 126.58 | 245.09 | 217.23 | 193.52 | 124.66 | 184.63 | 163.62 | 220.55 | 146.35 | 244.07 | |
Rb | 84.17 | 110.26 | 126.99 | 97.51 | 103.09 | 121.08 | 110.71 | 95.65 | 146.25 | 115.61 | |
Sr | 153.91 | 40.41 | 100.01 | 139.12 | 88.65 | 124.32 | 85.45 | 110.10 | 76.77 | 110.41 | |
Zn | 61.50 | 113.69 | 140.40 | 94.79 | 32.51 | 98.36 | 65.02 | 132.84 | 82.74 | 109.51 | |
Cr | 67.76 | 82.80 | 113.98 | 76.43 | 29.17 | 108.22 | 86.21 | 93.98 | 98.95 | 124.99 | |
V | 57.61 | 100.72 | 92.17 | 76.86 | 41.82 | 89.66 | 82.07 | 90.73 | 88.05 | 98.66 | |
Ni | 29.87 | 33.92 | 53.64 | 39.89 | 33.34 | 42.75 | 34.98 | 46.97 | 37.58 | 52.77 | |
Co | 21.42 | 30.59 | 23.84 | 27.09 | 24.60 | 33.07 | 25.31 | 31.65 | 33.56 | 28.94 | |
Cu | 24.36 | 26.43 | 47.40 | 21.90 | 5.85 | 30.49 | 19.16 | 36.00 | 36.63 | 5.63 | |
Pb | 15.37 | 12.94 | 22.25 | 20.00 | 5.04 | 19.19 | 10.93 | 23.64 | 20.52 | 101.90 | |
Ga | 13.75 | 19.23 | 23.85 | 14.51 | 17.42 | 24.98 | 20.55 | 20.01 | 22.00 | 27.65 | |
Y | 13.94 | 21.66 | 25.27 | 17.88 | 13.80 | 21.36 | 20.36 | 21.75 | 21.75 | 21.74 | |
Nb | 9.86 | 13.11 | 19.58 | 17.41 | 10.52 | 13.19 | 19.09 | 15.87 | 13.81 | 18.72 | |
Th | 6.35 | 7.64 | 18.57 | 7.77 | 5.68 | 10.76 | 11.67 | 12.45 | 9.48 | 16.85 | |
Ge | 1.13 | 5.36 | 4.77 | 8.19 | 57.78 | 1.49 | 3.85 | 6.99 | 1.08 | 6.55 | |
Hf | 3.24 | 4.05 | 11.43 | 5.69 | 2.06 | 6.79 | 6.94 | 11.87 | 11.48 | 1.39 | |
Sc | 23.97 | 1.06 | 0.48 | 12.32 | 0.23 | 1.46 | 9.29 | 0.97 | 2.57 | 0.23 | |
U | 2.59 | 6.09 | 4.29 | 2.40 | 2.11 | 4.74 | 2.27 | 2.67 | 2.82 | 1.75 | |
Ta | 0.61 | 1.37 | 1.87 | 0.74 | 1.44 | 1.37 | 0.95 | 1.27 | 1.42 | 1.46 | |
Mo | 0.61 | 1.08 | 0.88 | 0.75 | 0.37 | 1.02 | 0.74 | 0.78 | 0.91 | 0.84 | |
Cd | 0.22 | 0.16 | 0.96 | 0.18 | 1.05 | 0.74 | 0.08 | 0.50 | 0.36 | 0.20 | |
Bi | 0.01 | 0.02 | 0.04 | 0.25 | 0.24 | 0.02 | 0.12 | 0.09 | 0.02 | 0.16 |
4 讨论
4.1 化学风化与沉积再旋回
表3 化学风化及沉积再旋回判别参数Table 3 Chemical weathering and distinguishing parameters of sedimentary recycle |
参数 | 公式 | 风化 相关性 | 来源 | 须家河组 | 须二段 | 须三段 | 须四段 | 须五段 | 须六段 |
---|---|---|---|---|---|---|---|---|---|
CIA | Al2O3/(Al2O3+Na2O +K2O+CaO*)×100 | + | 文献[38] | 66.97~83.92 | 71.63 | 76.27 | 80.35 | 75.86 | 83.92 |
ICV | (Fe2O3+K2O+Na2O+CaO*+MgO+MnO+TiO2)/Al2O3 | - | 文献[40] | 0.79~1.44 | 1.13 | 1.17 | 0.84 | 1.13 | 0.79 |
CIW | Al2O3/(Al2O3+Na2O+CaO*)×100 | + | 文献[41] | 81.43~99.88 | 88.19 | 90.53 | 92.16 | 91.30 | 97.14 |
PIA | (Al2O3-K2O)/(Al2O3 +Na2O +CaO*-K2O)×100 | + | 文献[42] | 76.58~98.78 | 84.78 | 88.03 | 90.80 | 89.28 | 96.60 |
CIX | Al2O3/(Al2O3+Na2O+K2O)×100 | + | 文献[48] | 72.38~84.97 | 75.18 | 79.34 | 83.19 | 78.65 | 84.97 |
WIP | (2Na2O/0.35+MgO/0.9 +2K2O/0.25 +CaO*/0.7)×100 | - | 文献[49] | 29.84~50.93 | 45.30 | 33.89 | 34.29 | 39.74 | 29.84 |
MWPI | [(Na2O+K2O+CaO*+MgO)/(Na2O+K2O+CaO*+MgO +SiO2+Al2O3+Fe2O3)]×100 | - | 文献[50] | 6.29~12.58 | 9.23 | 8.58 | 7.16 | 8.75 | 6.30 |
CPA | (Al2O3)/(Al2O3+Na2O)×100 | + | 文献[51] | 89.76~99.51 | 93.60 | 95.01 | 95.92 | 95.30 | 98.55 |
|
图5 A—CN—K(a)和A—CNK—FM(b)三角图、ICV—CIA(c)和WIP—CIA(d)交会图[(a)底图据文献[42]修改,(b)底图据文献[57]修改,(c)底图据文献[58]修改,(d)底图据文献[43]修改]((a) base map is modified from Ref.[42], (b) base map is modified from Ref.[57], (c) base map is modified from Ref.[58], (d) base map is modified from Ref.[43]) Fig.5 Triangular plot of A-CN-K (a) and A-CNK-FM (b), Intersection diagram of ICV-CIA (c) and WIP-CIA (d) |