贵州省松桃杨家湾锰矿含锰岩系地质地球化学特征

Geological and Geochemical Characteristics of Manganese-bearing Rock Series of Yangjiawan Manganese Deposit,Songtao County,Guizhou Province

贵州松桃南华系"大塘坡式"锰矿经过多年的勘查研究,浅部已形成以西溪堡、李家湾、杨家湾为主的全新"锰三角"格局。杨家湾锰矿是该"锰三角"中一个大型锰矿床。通过对该矿区含锰岩系的地质地球化学特征研究,发现该区含锰岩系中见凝灰质等火山物质,同时具有热水成因的黄铁矿、重晶石、锰方解石等矿物组合。该锰矿在Fe-Mn-(Ni+Co+Cu)×10及P2O5-Y图解上均落在热水沉积区内,As、Sb、Ga、Ag、Ba、Zn、Co、Bi、W及Pb的含量较正常沉积岩明显偏高,且Co/Ni、Y/Ho及Nb/Ta比值均与海底黑烟囱热流体特征类似,该锰矿床稀土含量总体偏高,轻重稀土分异明显,轻稀土相对较富集,稀土配分曲线平缓,略向右倾斜,δEu(0.49～0.71)、δCe(0.94～1.25)及Ce/La-La/Yb图解也均表明热水参与的特征。此外,该锰矿δ13CPDB为-3.80‰～-4.17‰、δ18OPDB为-6.95‰～-8.78‰,据此估算成矿温度为54.2～65.7℃,为中低温热水条件。杨家湾锰矿为海底热水沉积成因。

＂Datangpo type＂ manganese deposits of Nanhua System studied in this paper are located in Songtao County of Guizhou Province.Based on years of exploration and research,there are three superficial deposits of Xixibao manganese deposit,Yangjiawan manganese deposit,Lijiawan manganese deposit,making up a new pattern of ＂Manganese Triangle＂,in which Yangjiawan manganese deposit is a medium-large one.Geological and geochemical characteristics of manganese-bearing rock series of Yangjiawan manganese deposit indicate that in manganese-bearing rock series exists volcanic material such as tuff,and mineral association of pyrite,barite and calcimangite,which shows a hydrothermal origin.Besides,this manganese ore falls on the hydrothermal deposition region according to illustrated diagrams of Fe-Mn-（Ni＋Co＋Cu）×10 and P2O5-Y,and contents of As,Sb,Ga,Ag,Ba,Zn,Co,Bi,W and Pb are higher than those of normal sedimentary rocks,moreover,ratios of Co/Ni,Y/Ho and Nb/Ta all show similar characteristics to hot fluid of ocean-floor black chimney.The overall content of rare earth elements of this manganese deposit is relatively high,and the differentiation of light and heavy rare earth are obvious,and distribution pattern is smooth,slightly lean to the right.In addition,δEu（0.49-0.71）,δCe（0.94-1.25） and Ce/La-La/Yb diagrams also show features of hydrothermal participation.Besides,δ13CPDB and δ18OPDB of the manganese deposit range from-3.80‰ to-4.17‰ and from-6.95‰ to 8.78‰,respectively;therefore,the mineralization temperatures are estimated from 54.2 to 65.7 ℃,belonging to the low and medium temperature hydrothermal condition.In conclusion,the authors consider that Yangjiawan manganese deposit is of hydrothermal genesis.