【作者】 张佩华；

【导师】 赵振华；

【作者基本信息】 中国科学院广州地球化学研究所 ， 元素地球化学， 2000， 博士

【摘要】 “东坪式”金矿系指产于华北克拉通北缘水泉沟碱性杂岩体中的一系列少硫化物、 富Te金矿床，是我国发现的特大型金矿的新类型。 碲在矿床中最高丰度达71 ppm，平均6．71 ppm，Te/Au平均比值0．72，Te丰度呈正 态负偏态分布，即主要分布在富金石英型矿石。Te、Au相关性、Te/Au比值、稀土元素 模式等在石英脉矿体和蚀变岩型矿体之间有显著区别：前者Te、Au绝对含量和Te/Au 比 值高(平均>0．7)、稀土总量低(<10 ppm)，后者贫Te、Te/Au 比值低(平均<0．5)、稀土 总量高(>20 ppm)。碲在石英脉矿体的水平、垂直空间与金显著正相关，相关系数、Te/Au 比值同时随矿石金品位的加富而增大，说明碲与金具有同一矿化富集中心。碲在矿石内主 要以AU、Ag、Pb 碲化物与含Ag自然金共生，它们在局部的矿物量相近，并分布于方铅 矿、黄铁矿、石英表面和裂隙，其中的“难溶金”与碲本身都具有回收价值。 除上述碲化物外，碲在本矿床形成罕见的碲银矿、Au2Te和种类繁多的未名碲化物、 碲酸盐等含氧盐，含氧盐进一步可分为含 Au、不含Au，包括 AuTeO3、Au2TeO4、AuTeO4 等以及水硫碲铅石、Zn2Te3O8、H2Pb2Fe4［TeO4］9.7－12H2O等，后二种为待申报的新矿物。 研究表明，这些碲含氧盐大多数为碲金矿、碲铅矿与硫化物共同氧化的产物，“难溶金” 矿物在氧化条件下发生分解，一般释放出自然金；由于金要么以自然金形式被“捕获”于 这些含氧盐，要么重新与碲形成Au－Te含氧盐，所以抑制了金的次生富集。 “东坪式”金矿的内生成矿可划分为两期四阶段，其中黄铁矿-石英阶段和硫化物-石 英阶段是跨矿物的主要形成阶段，显示其富集的阶段性与空间上的局域性。自然金-跨金 矿、碲铅矿-方铅矿与晚阶段碲银矿-自然银共生组合分析表明，本区碲逸度处于“自然碲 的不饱和”状态，并随成矿温度降低而减小。矿物组合、现代地热流体观察以及碲纳米化 挥发实验与流体包裹体、同位素示踪研究表明，Te、Pb、Au和部分硫化物来源于深部地 幔(岩浆活动)“脱气”形成的高挥发性、纳米态悬浮物流体，沿超壳断裂对区域合矿流 体的混合、沸腾过程对早期“矿胚”改造是形成“东坪式”金矿Au-Te元素组合富矿体的 形成机制。其地质地球化学特征介于典型“碱质类”浅成热液金矿床和大水沟独立碲矿床 之间，但成岩、成矿时差较长。碲的来源主要是区域地幔热柱活动及其岩浆“脱气”产物。更多还原

【Abstract】 Th Dongping-type gold deposit is named after a gold deposit in Dongping villagewas explored, with its gold ores rich in tellurium (Te in abbrev.) and short of sulfides,which has been proven characteristic for all other gold deposits in the Shuiquangousyenite batholith on the northem margin of North China craton.T is 71ppm in maximum and 6.71 ppm in average, respectively for the gold oresand tends to concentrate in high-grade ores of gold bearing quartz veins. The quartzvein orebody is different from auriferous metasomated syenite orebody in correlationcoeffiency and the ratio between Te and Au, along with REE contenis: the former ishigher in Te, Au grades, in the value of Te/Au ratio (>0.7 in average), and lower inREE content (<10 ppm), whereas the latter is lower in Te abundance, in the value ofTe/Au ratio (<0.5) and higher in REE content (>20ppm). Te is in positive correlationwith gold both at depth and in horizon profiles of the quartz vein bodies, whosecorrelation coefficiency and the ratio between Te and An increase along with theincrease of An grade, suggesting that Te has the same concentrative center as of Auin the quartz vein orebody. In gold ores, Te presents as tellurides of Au, Ag, Pb inassociation with native gold, occurring in surfaces or/and fissures of galena, pyriteand quartz minerals. Therefore, Te and the ’refractory gold’ are worth being extractedfrom these abundant tellurides.B ides the tellurides mentioned above that are common in gold deposits, Te isalso seen in such rare minerals as hessite, Au2Te and, a variety of unnamed telluritesand tellurates that may be subdivided into Au-bearing and Au free minerals. Theformer includes AtteO3, Au2TeO4, AuTeO4; and the latter schieffinilite, Zn2Te3O8,H2Pb2Fe4[TeO4]9.7-12H2O that were found by the author and are yet to be furtherstudied for acceptance by IMA-CNMMN as potential new minerals. Most of thesete1lurites and tellurates in these deposits are found to be products of coeval oxidationof calaverite, altaite and sufides, by Which ’refractory gold’ of Au tellurides will bereleased as naive gold. Most native gold released through oxidation of tellurides,however, will be trapped in the telluraes or tellurites; or be combined by Te intellurites or tellurates, which prevent gold of hyPergene from secondaxy enrichmentunder the supergene oxidation environrnenis.Of the fOux metallogenic stages of two periods, Te was mineralized only at bothpyrite-qUartz stage and base metal sulfides quaftz stage, demonstrating itsunsustainable in time and confinement to a small area. From mineral associations ofnative gold -calaverite, ga1ena -altaite in conunon, and native silver-hessite at the endof the sulfides quartz stage, it is concluded that Te, fugacity is in ’unstheated statefor native Te’ and will decline with the temperature of metallogeulc fluids decreased.It is inferred under observations on mineral paragenesis, modem geothermal fluids,and Te evaPoration experiments in nanometer scale particles, along with fluidinclusions and O,H,C,S isotope data that, Te, Pb, Au and parts of sulfides originatefrom deep under the crust during ’magtna degassing’ and are transported in volatilefluids made of suspended nanometer scaled particles. ms high temperthee fluldsmixed with regional auriferous groundwater in the crust-crossing faults, causingboiling of the fluid mixture and depositing Te, Au, Pb in the process of mixing andboiling. The precipitates of Te, Au, and Pb ’reworked’ and added Te, Au, Pb to theearier stages Au concentrates, forming rich ores of Au-Te association. Thismechwhsm is suPPorted by geological and geochemical characteristics of theDongping tyPe gold deposits, which range between tyPical epithermal gold depositsand the Dashuigou Te deposit of the mantle-degassing origin. Te is believed to comefrom the ’magma degassing’ during regional mantle plutne process in the northwestHebei, China.更多还原