胶东和鲁西地体发育大量的中生代金矿床,其金元素的来源一直是学术界争论的焦点,可能的来源方式为:交代岩石圈地幔、前寒武纪变质基底和中生代二长花岗岩.为了进一步厘定金的来源,文章从金的富集阶段模式和金矿床是金元素超常富集地质体的思想出发,运用金矿床的空间分布数据和空间分析的分形地质统计方法,进行了研究.研究结果发现,胶东金矿床(N=823)具有一阶段的空间分形分布模式,其分形维数α=0.726,具有单一来源或单一成因的特征;结合前人研究和克拉通破坏和西太平洋俯冲的地质背景,推断胶东金元素极有可能是单一的交代岩石圈地幔来源;而胶东地体西侧鲁西地体中发育的金矿床(N=139)则具有二阶段的空间分形分布模式,其分形维数分别为α1=1.630 和α2=0.850,具有 2 种金元素来源或 2 种成因类型的特征,可能分别对应着早前寒武纪变质岩及韧性剪切带有关金矿床和晚中生代岩浆活动有关金矿床空间分布的分形维数,后者的值与胶东地体的分形维数相近,结合前人研究,推测鲁西部分金矿床来源于交代岩石圈地幔的贡献,另一部分则可能来自于花岗质岩浆.
The Shazhangtu tin-copper polymetallic deposit is located in the central part of Inner Mongolia.It is a new discovery during the tin ore prospecting in the region in recent years.The tin ore bodies are tourmaline veins tourmalite and tourmaline-quartz altered rocks with cassiterite as the main ore mineral in veins or dissemination The copper ore bodies are tourmaline-quartz altered rocks and galena-sphalerite-chalcopyrite altered rocks with chalcopyrite as the main copper bearing mineral.Concealed diorite porphyrite was found in the deep part of the deposit by drilling.In order to strengthen the study on the ore-forming age and the source of ore-forming materi‐als of the tin-copper ore body,clarify the genetic type of the deposit,and further guide the prospecting work based on detailed field investigation and indoor identification,La-MC-ICP-MS U-Pb dating and electron probe composition analysis of cassiterite were carried out,and also the sulfur isotope analyses of associated sulfide minerals.The result shows that the 206 Pb/ 207 Pb- 238 U/ 207 Pb isochron age of cassiterite is （316.3±8.9）Ma,which is the product of the Late Carboniferous stage of Hercynian,electron probe analytical data of cassiterite illustrate tha the cassiterite is from a hydrothermal deposit.The sulfur isotope results show that the δ 34 S value of sulfide ranges from 0.43‰ to 7.34‰,with an average value of 4.39‰,indicating that the sulfide has the characteristics of mixed sulfur source.In conclusion,it is preliminarily considered that the Shazhangtu tin-copper deposit is a mag‐matic hydrothermal type related to dioritic porphyrite magmatic intrusion.
The Xinling Pb-Zn-Ag deposit is located in the northeastern North China Craton.The ore bodies are hosted in the Paleoproterozoic Liaohe Group metamorphic rock,and are controlled by faults.In order to obtain diagenetic and metallogenic ages,source of ore-forming fluids and materials of the Xinling deposit and its genetic relationship with Mesozoic magmatic activity,a systematic studies of deposit geology,chronology and isotopic chemistry have been carried out in this paper.We present LA-ICP-MS zircon U-Pb age of （227.3±1.5）Ma for ore-related granite porphyry,Rb-Sr isochron age of （222.9±2.9）Ma for five sphalerite samples with initial Sr isotope ratio of 0.7104,which represent the Late Triassic diagenetic and metallogenic ages for the Xinling deposit.The δ 18 O W and δD W values of the ore-forming fluids vary from 4.7‰ to 7.6‰,and -97.7‰ to -82.0‰,respectively,indicating that the ore-forming fluid was mainly derived from magmatic fluid.The ~3He/~4He ratio of fluid inclusions in ore pyrite ranges from 0.15 to 0.21 Ra,further indicates that the ore-forming fluid was a mixing product of crusta and mantle-derived fluids.LA-ICP-MS in-situ δ 34 S values of pyrite sample range from+3.9‰to+7.2‰,with an average of+5.5‰.The lead isotopic compositions of the six sphalerite samples are 206 Pb/ 204 Pb=17.534～17.822, 207 Pb/ 204 Pb=15.527～15.591, 208 Pb/ 204 Pb=37.851～38.162.The K-feldspar Pb isotopic compositions of the two granite porphyry samples are 206 Pb/ 204 Pb=17.411～17.500, 207 Pb/ 204 Pb=15.498～15.509,and 208 Pb/ 204 Pb=37.519～37.614.S-Pb isotope composition indicates that the ore-forming material was mainly derived from the Late Triassic magma with minor Liaohe Group metamorphic rock.
石家金矿床位于胶东中部蓬莱-栖霞成矿带北段,是一个赋存于中生代花岗岩中受构造带控制的石英脉型金矿床.由于多年开采,矿区浅部资源已近于枯竭,亟需向深部拓展找矿空间.黄铁矿是石家金矿床最常见的金属矿物,也是最重要的载金矿物,其标型特征对深部找矿预测具有十分重要的意义.文章对采自石家金矿床326 号矿脉不同海拔标高主成矿阶段黄铁矿的热电性与晶胞参数进行了分析,结果表明:在-595～-165 m标高内,石家金矿床黄铁矿的热电导型以P型为主,占比约 97.5%,表明目前揭露的矿体处于矿化系统的上部或顶部;热电系数(α)变化于-288.3～304.9 μV/℃,较大的离散范围表明矿体垂向延伸较大;黄铁矿热电系数离散度为 8%～68%,较低的离散度指示黄铁矿形成于较为稳定的条件之下,并且矿化程度较好;利用热电系数计算黄铁矿的形成温度集中于 210～250℃,指示石家金矿床属于中温矿床;根据热电系数计算的矿体剥蚀率(γ)为 25.5%～34.0%,表明矿体未遭受大规模的剥蚀,向下仍有较大延伸.黄铁矿晶胞参数a0 介于 0.5418～0.5422 nm,略大于理论值(0.54176 nm).结合黄铁矿热电导型与前人研究,认为晶胞参数的变大可能与As类质同象替代S有关.综合分析认为,石家金矿床在-600 m以下的深部仍具有良好的找矿前景.
单个流体包裹体成分LA-ICP-MS分析在精准示踪成矿物质来源和精细刻画成矿过程方面具有独特优势,但已有研究主要聚焦于透明的脉石矿物中的流体包裹体,对用于矿石矿物较少,二者之间有何异同特别是谁更能代表成矿流体组成目前研究薄弱.闪锌矿是岩浆热液矿床和MVT型矿床中常见的矿石矿物,其通常发育流体包裹体并在透射光下具有透明-半透明特征,是研究流体包裹体较为理想的矿石矿物.文章选择南岭新田岭钨矿硫化物阶段的闪锌矿及共生石英为研究对象,开展流体包裹体成分LA-ICP-MS对比分析.分析结果显示,闪锌矿和石英中的流体包裹体组成存在较大差异,前者异常富Cu、Ag和Sn等金属元素,后者富Li、B、Na、K、Rb、Sr、Cs和Pb等元素.结合闪锌矿本身微量元素特征,文章认为元素Cu、Ag和Sn的超常富集与其从寄主矿物扩散进入流体包裹体有关.在基于大离子亲石元素的流体成因类型判别图中,闪锌矿和石英中的流体包裹体组成均能有效示踪成矿流体来源,但后者示踪效果更好.总体而言,共生石英中流体包裹体组成可能更能代表成矿流体组成,闪锌矿因其莫氏硬度较低、金属元素含量高等原因,元素易发生后期扩散/改变,流体包裹体组成可能不能代表真实流体信息.在研究矿石矿物流体包裹体时,需谨慎对待某些元素的超常富集.综合研究脉石矿物流体包裹体和矿石矿物本身元素组成是成矿流体研究更准确的手段.
