楚雄盆地六苴上白垩统马头山组大村段沉积地球化学

Sedimentary geochemistry of the Dacun Member in the Upper Cretaceous Matoushan Formation in Liuju,Chuxiong Basin

上白垩统马头山组大村段是云南楚雄盆地的主要含铜层位之一。通过六苴zK24401钻孔岩芯样品地球化学研究，认为大村段是半干旱-半潮湿气候条件下盆地边缘的湖泊沉积形成，沉积物距物源区较近，其沉积演化过程与物源区具有一致性。主元素组成的W（SiO2＋Al2Oa＋K2O＋Na2O）占49．64％～81．84％，n（SiO2）／n（Al2O3）平均值为3．65，n（Al）／n（Al＋Fe＋Mn）值为0．71～0．78，n（Si）／n（Si＋Al＋Fe）值为0．69～0．87，反映出沉积物物源以陆源为主；n（Al2O3）／n．（Al2O3＋Fe3O3）值为0．79～0．91，显示了大陆边缘沉积环境的特点；K2O／Na2O多大于1，表明物源区主要为偏酸性的花岗质岩石。沉积旋回造成多层泥页岩中Cu、Zn、Sb等元素初始富集。稀土总量ω（EREE）为104．12×10^-6～181．69×10^-6，n（La）N／n（Yb）N〉1，轻重稀土分异程度较高，稀土配分模式为Eu、Ce亏损——轻稀土富集右斜型。

The Dacun Member of the Upper Cretaceous Matoushan Formation is one of the major Cu-bearing horizons in the Chuxiong Basin. Based on geochemical research of ZK24401 drilled core samples, it has believed that the Dacun Member is formed by lake depositing on the edge of the basin under semiarid and semihumid climate. The sediments are closer to matters source region with the sedimentary evolving processes similar to that of the source region. The Dacun Member rocks are characterized by major elements composition of （SiO2＋Al2O3＋K2O＋Na2O） ranging from 49. 64% to 81.84%,and average n（SiO2）/n（Al2O3） being 3. 65 with n（Al）/n（Al＋Fe＋Mn） ranging from 0. 71 to 0. 78,n（Si）/n（Si＋Al＋Fe） ranging from 0. 69 to 0. 87 that indicates major sediments from terrigenous sources, n（Al2O3）/n（Al2O3＋Fe2O3） ranging from 0.79 to 0. 91 that showes sediments deposited on continental margin, most K2O/Na2O values are higher than 1 which inferres most acidic granites occupied matters souce region. Cu, Zn, Sb are preliminary enriched in multilayered shales by sedimentary cycles. The XREE of the rocks ranges from 104. 12 ×10^-6to 181.69× 10^-6 with n（La）N/n（Yb）Nhigher than 1 and high ratio of LREE to HREE. Chondrite-normalized REE distribution patterns show right oblique to the HREE side with depleted Eu, Ce and enriched LREE.