黑龙江漠河县八里房金矿床地球化学特征及成因

Geochemistry and Ore Genesis of the Balifang Gold Deposit in Mohe,Heilongjiang Province

八里房金矿床位于黑龙江省漠河县西北部，是一个新发现的金矿床。矿体赋存于闪长岩和中侏罗统额木尔河组长石砂岩中，矿石由含金、黄铁矿的长石砂岩和石英细脉组成。岩石地球化学研究表明：闪长岩稀土总量中到低，富集大离子亲石元素（如K、Rb、Ba）和化学性质活泼不相容元素（如U、Th、Pb），相对亏损高场强元素（如Ta、Nb、P、Sr、Ti），球粒陨石标准化稀土配分模式为轻稀土富集、重稀土亏损的右倾型，具有弱的Eu负异常（6Eu平均值为0．8），无Ce异常（8Ce=0．9～1．0），元素地球化学性质反映出八里房闪长岩具有岛弧岩浆岩的特征；长石砂岩稀土元素总量（∑REE）变化较大，具弱Eu负异常（8Eu平均值为0．8），无Ce异常（8Ce=0．9～1．0），为活动边缘砂岩系列。含金石英脉中流体包裹体有气液两相、含CO2三相和纯CO2流体包裹体3种类型。气液两相包裹体均一温度为107．9～247．4℃，盐度（w（NaCl））为3．05％～8．55％，密度为0．84～1．00g·cm^-3；含CO2三相包裹体完全均一温度为269．8～332．7C，盐度为4．41％～10．29％，成矿流体为中低温、低盐度的热液流体体系。基于矿床地质特征、岩石地球化学和成矿流体特征的研究，笔者认为八里房金矿床为造山型金矿床。

Balifang gold deposit, located in the northwest part of Heilongjiang Province, is one of the recently discovered gold deposits. The ore bodies are hosted in the diorite and arkose of the Middle Jurassic Emuerhe Formation. The ore types include gold and pyrite bearing arkoses and quartz veins. Studies of petrogeochemistry indicate that the diorite, is with medium to low ∑REE concentrations, enriched in LILE （such as K, Rb, Ba） and more mobile incompatible elements （such as U, Th, Pb）, relatively depleting in HFSE （such as Ta, Nb, P, Sr, Ti）. The chondrite-normalized REE patterns of the diorite samples display pronounced LREE enrichment and HREE depletion, slightly negative Eu anomalies （average 0.82）, and no Ce anomalies （δCe-0.97-1.07）. Geochemical characters imply that the Balifang diorite intrusion has the similar geologic characteristic to the island-arc and active continental margin magma. The arkoses has a wide range of ∑REE concentrations, slightly negative Eu anomalies （average 0. 76）, and no Ce anomalies （aCe= 0. 91~0. 99）. The arkoses belongs to the sandstone series in active margin. Fluid inclusions in quartz veins can be classified into aqueous two- phase, CO2-bearing three-phase and pure CO2 types. The homogenization temperatures of aqueous two- phase and CO2-bearing three-phase inclusions range from 107.9 to 247.4 ℃, 269.8 to 332.7 ℃ ,and the salinities（zv（NaC1）） range from 3.05O//oo to 8. 55G, 4. 41 to 10. 29%. The ore-forming fluids are the hydrothermal system with medium-low temperature and low salinity. Combined with the geological characteristics of ore deposit, petrogeochemistry and ore-forming fluids, it can be concluded that the Balifang gold deposit belongs to the orogenic gold deposit.