摘要
三保钨钼矿床位于政和—大浦大断裂之东侧。矿体产于花岗斑岩(85Ma)与侏罗系南园组流纹质晶屑凝灰熔岩的内、外接触带中,属中—高温石英脉型矿床。石英包裹体的δD_(H_2O)值为-4l—-47‰,δ^(18)O_(H_2O)值为-6.0—-7.3‰,表明成矿热液是来自大气降水。根据矿体中δ^(34)S值和黑钨矿中富Nb_2O_5、贫Ta_2O_5,辉钼中Re及黄铁矿中Co高、Ni低等特征,证实成矿物质与同熔型花岗斑岩是同一来源的。花岗斑岩中除W、Mo含量较高外,Cr、Ba、Re的含量和∑Ce/∑Y比值、磁铁矿-(?)石-锆石等副矿物组合都与华南过渡型地壳同熔型花岗岩系列成因相似。根据上述资料推测本矿床成矿模式是:同熔型花岗斑岩形成时初步富集了矿质→地下水循环热液与花岗斑岩作用淋滤出矿质→转移到构造有利部位沉淀形成矿体。
The ore deposit in question lies within the Fujian-Zhejiang-Guangdong Cenozoic fault depression, on the east side of Zhenghe-Dapu fault. The orebodies occur in endo- and exo- contact zones between a granite porphyry (85Ma) and the rhyolitic crystal tufflava of Upper Jurassic Nanyuan Formation.The orebodies have the following characteristics; (1)δ^(18)O_(H_2O)= -3.3—11.7‰ and δD_(H_2O)-41—-120‰ within the field of meteoric hydrothermal fluids;δ^(34)S=1.89—-9.88‰;δ(34)S_(ES)= 4.9‰ at the endocontact zone and 3.8‰ at the exocontact zone respectively, suggesting a mixed crust-mantle sulfur source; (2) wolframite is rich in Nb_2O_5(0.12—1.81% )and poor in Ta_2O_5(0.0017—0.0024%), with low Ta_2O_5/Nb_2O_5 ratios(0.012—0.039);except for very few samples, the Re contents of molybdenite are mostly lower than 15 ppm; Co contents of pyrite are 24—153 ppm, and Ni<10ppm; (3)the ore-formig temperatures of wolframite and molybdenite are 270—297℃ and 240—265℃ respectively, showing gradually decreasing tendency from endo-contact zone to exocontact zone.The granite porphyry has four features; (l)SiO_2>75%, (K_2O+ Na_2O)>8.5% and Na_2O/K_2O = 0.77,Al_2O_3/(K_2O + Na_2O + CaO)(mol) = 1.05; (2) it is of magnetite-orthite-sphene-zircon type granite with magnetite being dominant; (3)∑REE =174ppm, ∑Ce/∑Y=4.77 and δEu=0.51, with moderate Eu deficiency and asymmetric 'V'-shaped distribution curve; (4) the intrusive body is rich in W, Mo, Sn, Be, Ba etc. and poor in Cu, Ni.The researches have led the author to the following conclusions. (1) The granite porphyry is genetically of transitional crustal syntectic type and also serves as the supplier of the ore materials; and (2) the infiltrating metasomatism of granite porphyry by meteoric-hydrothermal fluids leached out the ore materials which formed quartz vein type tungsten-molybdenite deposits at medium-high temperatures.
出处
《矿床地质》
CAS
CSCD
北大核心
1989年第1期29-38,共10页
Mineral Deposits
