陕南屈家山锰矿热水沉积成因:元素地球化学和C-O同位素证据  

Hydrothermal Sedimentary Origin of the Qujiashan Manganese Deposit in the South of Shaanxi Province:Evidence of Elemental Geochemistry and C-O Isotope

作　　者：黄建国[1] 李虎杰[1] 任涛[2] HUANG Jianguo;LI Hujie;REN Tao(School of Environment and Resource,Southwest University of Science and Technology,Mianyang 621010,Sichuan,China;Faculty of Land and Resources Engineering,Kunming University of Science and Technology,Kunming 650093,Yunnan,China)

机构地区：[1]西南科技大学环境与资源学院,四川绵阳621010 [2]昆明理工大学国土资源工程学院,云南昆明650093

出　　处：《大地构造与成矿学》2021年第2期345-355,共11页Geotectonica et Metallogenia

基　　金：中国地质调查局项目(资[2013]01-036-078);西南科技大学博士基金(14zx7126)联合资助。

摘　　要：陕南屈家山锰矿属于“巴山锰矿带”中段,赋存于上震旦统陡山沱组第3岩性段(Z2d3)紫红色钙质页岩中。矿石具有粒状(纤维)变晶、微粒泥质、微晶质(含碎屑)、胶状及条带状、微细纹层理、顺层揉皱、脉状、网脉状等热水同生沉积组构。含矿岩系中矿石的Fe/Ti、(Fe+Mn)/Ti及Al/(Al+Fe+Mn)值依次为14.53~25.11(平均21.47)、230.79~412.68(平均332.44)和0.04~0.16(平均0.10),反映成矿作用为典型的热水沉积成因。矿石的Sr/Ba值(0.04~0.56,平均0.22)、U/Th值(0.27~0.80,平均0.47)、Ni/Co值(0.24~2.84,平均1.61)和V/(V+Ni)值(0.63~0.69,平均0.66)及logU-logTh关系图解均反映其有热水沉积特征及氧化、次富氧(或贫氧)的沉积环境。矿石的稀土元素总量为98.38~125.66μg/g,平均110.31μg/g,δEu为0.93~1.04(平均1.00),δCe为0.91~1.03(平均0.98)。菱锰矿的δ^(13)CPDB值为–8.2‰~–20.7‰(平均–11.7‰),δ^(18)OSMOW值为14.3‰~18.7‰(平均17.1‰),指示屈家山锰矿具有深源(上地幔)碳的特征,成矿时形成于拉张环境,并非正常沉积的海相环境,推测有深部热水的加入,通过估算沉积成矿时古海水的温度为78.9~126℃,平均97.6℃。The Qujiashan manganese deposit,which occurs in the middle section of“Bashan Manganese Ore Belt”,is located at the junction of Ziyang and Zhenba counties of the southern Shaanxi province.The manganese ore bodies of the deposit lie in the purple-red calcareous shale of the third Member of the Doushantuo Group of the Upper Sinian System(Z_(2)d^(3)).The ores exhibit hydrothermal syngenetic sedimentary fabric,such as granular fibroblastic,fine grain politic,(clastics)microlitic,colloidal texture and banded,micro-grain,bedding wrinkle,veined,net veined structure etc.The Fe/Ti,(Fe+Mn)/Ti and Al/(Al+Fe+Mn)ratios of the ores wary in ranges of 14.53–25.11(average 21.47),230.79–412.68(average 332.44)and 0.04–0.16(average 0.10),respectively,suggestive of a typical hydrothermal sedimentary origin.The overall Sr/Ba(0.04–0.56,average 0.22),U/Th(0.27–0.80,average 0.47),Ni/Co(0.24–2.82,average 1.61)and V/(V+Ni)(0.63–0.69,average 0.66)ratios and U-Th relationship demonstrate that the ores were hydrothermally deposited under varied oxidation-reduction condition.ΣREE contents of the ores vary from 98.38 to 125.66μg/g,with an average of 110.31μg/g,δEu varies from 0.93 to 1.04(1.00 on average);δCe varies from 0.91 to 1.03(0.98 on average);δ^(13)CPDB(‰)andδ^(18)OSMOW(‰)of rhodochrosite range form–8.2 to–20.7(–11.7 on average)and 14.3 to 18.7(17.1 on average),respectively.C-O isotope characteristics of the ores show that carbon in the ores of the Qujiashan manganese deposit may have a deep source(upper mantle),and therefore,the deposit was likely formed under extensional environment with the involvement of deep hot water.The temperature of the paleoseawater during the sedimentary mineralization is estimated to be 78.9–126℃(average 97.6℃).

关 键 词：屈家山锰矿 大巴山 含锰岩系 C-O同位素 热水沉积成因 

分 类 号：P611[天文地球—矿床学] P597[天文地球—地质学]