【作者】 石文杰；

【导师】 魏俊浩；

【作者基本信息】 中国地质大学 ， 矿产普查与勘探， 2014， 博士

【摘要】 山东省位于华北克拉通东南缘,是我国重要的黄金产地之一,以沂沭断裂带为界,可分为鲁西、鲁东地区。对于山东省中生代构造-岩浆活动与金成矿作用,前人的研究主要集中于胶东地区,其次为鲁西地区,而沂沭断裂带作为华北克拉通东部最主要的大型走滑构造与骨干断裂,分别控制了上述邻沂与胶东等两个较大的金矿矿集区。论文以鲁西沂南、沂沭断裂带内龙泉站以及鲁东五莲地区金矿床及白垩纪中酸性杂岩体以及基性脉岩为研究对象,以详细的野外地质调查以及矿床地质特征分析为基础,并通过详细的矿石学、岩相学、锆石U-Pb年代学、黄铁矿Rb-Sr年代学、岩石地球化学及Sr-Nd-Pb-S-H-O-He-Ar同位素地球化学研究,探讨了与白垩纪金成矿相关的岩浆作用的成因与地球动力学背景,并对区内鲁西沂南铜井、沂沭断裂带内龙泉站以及鲁东五莲七宝山等典型金矿床开展了成矿流体、成矿物质来源的多元联合示踪研究,分析了成矿流体及成矿物质来源,结合上述研究成果探讨了区内构造-岩浆活动与金成矿等地质事件之间的成因联系,取得的主要结论如下：1.沂沐断裂带内龙泉站金矿区内发育了大量规模不等的中基性脉岩,岩性主要包括辉长岩、辉绿岩、闪长玢岩等为主。脉岩锆石LA-ICP-MS U-Pb年龄值可分为四组：2453±44-2552±47Ma、1852±44-1900±44Ma、730±8Ma及131±2Ma,其中131±2Ma代表了脉岩的形成年龄,形成于早白垩世。脉岩SiO2(47.54%～51.77%)含量变化较大,且具有较低的MgO(Mg#=40-49).Na20+K20(2.17%-3.43%).A1203(11.23%-13.58%).Cr(89.5×10-6-127×10-6).Ni(69.4×10-6-90.4×10-6)及较高的Fe203(13.57%-16.56%).Ti02(1.58%-3.20%). Ca0(8.99%-9.59%).Na2O/K20(1.77-8.03)。岩石微量元素组成(含稀土元素)富集Rb、Ba、Th、U等大离子亲石元素(LILE)和轻稀土元素(LREE),另外,岩石还相对富集高场强元素(HFSE),不具有明显的Nb、Ta、Zr、Hf负异常,岩石属于拉斑玄武岩系列岩石。脉岩(87Sr/86Sr)i(0.71019-0.71676)变化较大,对应的εNd(t)值(-8.66--4.30)与T2DM(1272-1625Ma)变化相对较小,其Sr-Nd组成位于原始地幔与大陆上地壳之间,且Nd同位素模式年龄相对于晚于华北克拉通地壳强烈的增生期,Pb同位素((206Pb/204Pb)i=17.7006-18.2049.(207Pb/204Pb)i=15.4781-15.5627.(208Pb/204Pb)i=38.2248-40.1191)变化较大,介于扬子与华北克拉通基底之间。主微量元素以及同位素综合研究结果表明,沂沭断裂带内基性脉岩为早白垩世强烈伸展背景下软流圈地幔部分熔融产生的岩浆与上地壳混染与分离结晶作用的产物。成岩构造背景与早白垩世郯庐断裂带的左行走滑所引起的岩石圈引张有关,同时也指示华北克拉通东部由挤压向伸展构造体制转换的时限不晚于130Ma。2.鲁西沂南铜井闪长玢岩为高钾钙碱性准铝质岩石,具富钠、高Mg#、富集Rb、Ba、U、Sr等大离子亲石元素(LILEs)与轻稀土元素(LREEs),亏损Nb、Ta、Ti等高场强元素(HFSEs)等特征,且基本无负Eu异常。岩石富集放射性成因铅((206Pb/204Pb)i=16.917-17.956),高(87Sr/86Sr)i (0.707105-0.70788)、低εNd(t)(-15.13--10.23)。主微量元素、Sr-Nd-Pb同位素综合研究表明,沂南闪长玢岩主要起源于富集岩石圈地幔,并伴随有陆壳物质的参与。鲁东七宝山早期次火山岩属于钾玄岩系准铝质岩石,Si02含量变化范围较大,富碱、低Mg#,富集Rb、Ba、Th等大离子亲石元素(LILEs),强烈亏损Nb、Zr、Ti等高场强元素(HFSEs),无-弱负Eu异常,具有相对较高的(87Sr/86Sr)i (0.7090-0.70920),低εNd(t)(-15.17--16.41)。而晚期次火山岩则属于高钾钙碱性弱过铝质岩石,明显富硅,相对高Mg#、富钾,轻重稀土分馏程度以及稀土总量低于早期次火山岩,但重稀土相对于早期岩石偏高,且具有正Eu异常,其(87Sr/86Sr)i (0.70875-0.70879)则与早期次火山岩较为一致。主微量元素、Sr-Nd同位素综合研究表明,早期次火山岩主要来源富集地幔的部分熔融,而晚期次火山岩则主要来源于镁铁质下地壳,可能有少量的幔源组分加入。3.研究区内龙泉站蚀变岩型金矿床黄铁矿Rb-Sr等时线年龄为96±2Ma,确证了华北克拉通东南缘可能存在晚白垩世金成矿作用。沂沭断裂带西侧沂南金场矽卡岩型金矿床辉钼矿Re-Os年龄为128±1Ma,早、晚矽卡岩阶段黑云母Rb-Sr年龄分别为133±6Ma、128±2Ma,与矿区二长花岗斑岩(126～128Ma)、花岗斑岩(127Ma、133Ma两期)等LA-ICP-MS锆石U-Pb年龄在误差范围内一致,二者无时差或较小(<5Ma)；铜井金矿床矿石中锆石U-Pb年代学获得与成矿关系密切的闪长玢岩的成岩年龄为129±4Ma左右,并结合区域内相邻矿床的年代学资料,推测成矿年龄为120Ma,与铜井闪长玢岩锆石U-Pb年龄(128～129Ma)基本一致,表明成岩成矿关系密切。七宝山隐爆角砾岩型金矿床单颗粒黄铁矿Rb-Sr年代(117Ma±),表明成矿时代为早白垩世产物,与区内晚期石英闪长玢岩黑云母K-Ar年龄(124.1Ma)时差较小,成岩成矿时代较为一致,为七宝山金矿成矿作用与晚期次火山岩有关提供了年代学制约。4.龙泉站含金石英脉中石英的6DH2O值为-77‰,对应的δ18OH2o值为+1.77‰～+4.07‰；七宝山金矿主成矿期热液胶结物中的石英δDG2O为-78.6‰--48.14‰,δ18OH2O值为+3.05‰～+5.77‰；沂南铜井形成金的石英-硫化物阶段石英的H-O同位素组成为δDH2O=-87‰,δ18OH2O=-0.4‰区内金矿主成矿期成矿流体主要来源于岩浆水。龙泉站金矿黄铁矿流体包裹体He-Ar同位素组成3He/4He(R/Ra)为0.14-0.78Ra,40Ar/36Ar比值为482-1811,40Ar*/4He比值为0.078～0.272；沂南金矿3He/4He(R/Ra)比值为0.11-1.02,40Ar/36Ar为364-458,40Ar*/4He比值为0.154～0.735；七宝山3He/4He(R/Ra)为0.187-0.194Ra,40Ar/36Ar比值为291-842,40Ar*/4He比值为0-0.04。根据根据壳-幔混合二元模型计算得到龙泉站金矿幔源He所占比例为1.6-9.6%,沂南金矿为1.3-12.6%,七宝山为2.3%。龙泉站金矿放射成因的Ar的比例范围为38.7%～83.7%,沂南铜井金矿为18.8%～35.5%,七宝山金矿为0～64.9%,上述三个矿床中对应的大气Ar的贡献率分别为16.3%～61.3%、64.5%～81.2%、35.1%～100%,上述结果显示龙泉站金矿大气Ar与放射性成因Ar的贡献率差别不大,而沂南与七宝山金矿的放射性成因Ar的参与量远小于大气Ar。综上所述,区内龙泉站金矿主要为壳源流体,沂南金矿成矿流体为壳幔混合成因流体,其幔源组分参与的比例与胶东地区金矿类似,而七宝山金矿则以大气降水为主。另外,七宝山与沂南金矿成矿流体中均有大气降水参与,从而表现出相对较低的40Ar/36Ar,与胶莱盆地内的蓬家夼、发云夼金矿成矿流体的He-Ar同位素组成较为类似。区内龙泉站、沂南铜井以及七宝山金矿床硫化物的δ34S分别为0.9%o-4.4‰、1.53%o-5.6%o和0.3‰～5.89‰,具有岩浆硫的特征。龙泉站金矿3硫化物的n(206Pb)/n(204Pb)=15.779-19.037,n(207Pb)/n(204Pb)=15.076-15.643,n(208Pb)/n(204Pb)=36.744-40.488,3件赋矿围岩(新太古代二长花岗岩)校正后为(206Pb/204Pb)i=15.40-17.754,(207Pb/204Pb)i=15.053-15.472,(208Pb/204Pb)i=35.734-37.801,龙泉站金矿床Pb同位素组成与校正后的围岩Pb同位素组成具有明显的差别,研究表明成矿物质主要来源于壳源；沂南铜井金矿床的10件硫化物的n(206Pb)/n(204Pb)=19.04-23.08,n(207Pb)/n(204Pb):15.69-16.30,n(208Pb)/n(204Pb)=38.40-41.46,与成矿关系密切的2件闪长玢岩的Pb同位素组成为n(206Pb)/n(204Pb)=17.855-17.956,n(207Pb)/n(204Pb)=15.505-15.528,n(208Pb)/n(204Pb)=37.826-37.883,沂南铜井金矿床硫化物的Pb同位素组成明显大于校正后闪长玢岩的Pb同位素组成,但二者Pb呈明显的线性分布趋势,表明矿石Pb主要由成矿母岩以及富集放射性成因Pb的地壳物质等两端元混合而成；七宝山金矿7件硫化物的n(206Pb)/n(204Pb)=16.624-17.725,n(207Pb)/n(204Pb)=15.238-15.512,n(208Pb)/n(204Pb)=36.414-37.721,矿区内早白垩世石英二长岩、安山玢岩与粗面岩的Pb同位素组成为n(206Pb)/n(204Pb)=16.485-17.056,n(207Pb)/n(204Pb)=15.149-15.388,n(208Pb)/n(204Pb)=36.445-37.484,七宝山金矿床Pb同位素组成与区内晚期火山-次火山岩Pb同位素组成基本相似,反映二者具有成因关系,也即成矿物质主要来源于岩浆活动。5.高精度成岩成矿年代学表明研究区内金矿主要存在两期成矿作用,分别为早白垩世与晚白垩世,与早白垩世金矿成矿有关的岩体成岩时代略早或同期,为早白垩世引张背景下富集地幔或地壳来源的浅成次火山侵入杂岩,属于高钾钙碱性系列岩石。金矿成矿流体与成矿物质与岩浆活动关系密切。尽管目前沂沭断裂带内晚白垩世矿内没有发现与金成矿作用关系密切的岩浆活动,但矿床地球化学特征指示金矿成矿流体与成矿物质均具有岩浆来源特征。根据矿床的矿化蚀变与岩浆活动的时空及成因关系,论文建立了沂沭断裂带及邻区早白垩世矽卡岩型金铜矿床+隐爆角砾岩型金铜矿床以及晚白垩世与岩浆热液有关的蚀变岩型金矿床的两阶段成矿模式。更多还原

【Abstract】 The Shandong province hosts the largest gold producing region in the southeastern margin of North China Craton. It is separated by the Tan-Lu fault into two distinct domains, namely, the Luxi to the west and the Jiaodong to the east. In addition, the big gold districts in Jiaodong and Luxi are all controlled by the Tan-Lu fault. Those gold deposits in Jiaodong and Luxi regions have been studied to a varying degree by many previous researches and many models have been developed to focus on their genesis, and the nature and extent of gold metallogeny between Luxi and Jiaodong regions display marked contrast. However, the gold deposits occurred in the the Yi-Shu metallogenic belt have not been well understood so far. In this study, we focus on the Tongjing gold deposit(Luxi), Longquanzhan gold deposit(the Yishu metallogenic belt) and Qibaoshan gold deposit(Ludong) in the middle segement of Tan-Lu fault zone, southeastern North China Craton. Based the detail field investigation of the Tongjing, Longquanzhan and Qibaoshan gold deposits, we present the zircon U-Pb age, major and trace element geochemistry, and Sr-Nd-Pb isotope compositions for the mafic dykes from the Longquanzhan gold district, the pyrite Rb-Sr chronology, S-Pb-He-Ar isotope data of ores from Tongjing, Longquanzhan and Qibaoshan gold deposits. These result are used to (1) document the Early and Late Cretaceous magmatisms and gold metallogenic events,(2) study the petrogenesis, source and geodynamic setting of the Early Cretaceous intrusives, and (3) discussed the magmatic sources for the ore fluids and metal concerning the Cretaceous gold ore system and analyzed the genetic links between gold metallogenesis and magmatism. The main results and conclusions are summarized as follows:(1) The mafic dikes are widely distributed in the Longquanzhan gold district, and they are mainly gabbro, diabase and diorite-porphyrite. LA-ICP-MS zircon U-Pb dating on the gabbro dike s in the Yishu fault zone reveals that they formed at131±2Ma with four major groups of inherited ages at2453±44-2552±47Ma,1852±44-1900±44Ma and730±8Ma. These gabbro dikes exhibit a wide range of SiO2and are characterized by Fe2O3, TiO2, CaO, Na2O/K2O and low abundance of MgO(Mg#=40-49), Na2O+K2O, A12O3, Cr, Ni. They are enriched in large ion lithophile elements (Rb, Ba, Th, U) and light rare earth elements without significant Eu anomalies, and depleted in high field strength elements, they are all belong to the tholeiitic series rocks. All samples show a wide range of Sr compositions with high87Sr/86Sr (0.71019-0.71676),d(t)(-8.66--4.30) and large T2DM ages (1272-1625Ma). Their Pb isotope compositions show a wide range ((206Pb/204Pb)i=17.7006-18.2049,(207Pb/204Pb)i=15.4781-15.5627,(208Pb/204Pb)i=38.2248-40.1191). In combination with the mineralogy, geochemistry and Sr-Nd-Pb isotope compositions, we contend that the gabbro dikes could have originated from partial melting of the upwelling asthenospheric mantle, with a small amount of crustal contamination. Dynamical background is probably related to the second extensional sinistral strike-slip movement of Tan-Lu fault system, which triggered the upwelling asenospheric mantle. Meanwhile, the chronology of mafic dikes also provide the time constraints for the transition from compressional to extensional mechanism.(2) Whole-rock geochemical data show that the Tongjing diorite-porphyrite can be classified as high-potassium calc-alkaline metaluminous rock, which are characterized by high Na2O content and high abundance of Mg#, and they are also enriched in LILE and LREE, and depleted in heavy earth elements (HREE) and HFSE, without significant Eu anomalies. In addition, the studied intrusion exhibit more radiogenic lead ((206Pb/204Pb)i=16.917-17.956), and are characterized by (87Sr/86Sr)i ranging from0.707105to0.70788, low εNd(t) values from-15.17to-16.41. In combination with the mineralogy, geochemistry and Sr-Nd-Pb isotopic compositions of Tongjing diorite-porphyrite, we contend that the Tongjing diorite-porphyrite could have originated from the enriched mantle, accompanying with some crastual contamination. The Qibaoshan subvolcanic intrusions can be divided into two stages. The early stage subvocanic intrusion belong to the alkaline magma series in terms of K2O+Na2O contents, and to shoshonitic series based on their K2O content. They are further characterized by an wide range of SiO2content with relatively low Mg#, positive anomalies in Rb, Ba, and Th, and are depleted in high field strength elements (Nb, Zr, Ti), without significant Eu anomalies. They show uniformly high (87Sr/86Sr)i (0.70900-0.70920), low εNd(t) values (-15.17to-16.41). However, the late stage subvocanic intrusions can be classified as high-potassium calc-alkaline and weaky peraluminous rocks. They show relatively high contents of SiO2and K2O and high abundance of Mg#, with lower degree of fractionation between LREE and HREE compared to those of the early stage subvolcanic intrusion, with positive Eu anomalies. In combination with the mineralogy, geochemistry and Sr-Nd isotopic compositions of Qibaoshan subvolcanic intrusions, we contend that the early stage subvolcanic intrusion could have originated from the partial melting of the enriched mantle, and lower mafic crust for the late stage subvolcanic intrusions.(3) The Longquanzhan gold deposit, as an important part of gold mineralization belt of the Yi-Shu fault zone, is the only one altered-fracture type gold deposit identified up to present. The Rb-Sr isotopic dating of10pyrites separated from the Longquanzhan gold deposit yielded an isochron age of96±2Ma (MSWD=1.2). It is the youngest high-precise age of gold deposits so far identified in Shandong Province. It may represent the Late cretaceous gold mineralization in Shandong Province. The Re-Os isochron age of molybdenite from Yinan Jinchang gold deposit was128±1Ma, and single grain and low background Rb-Sr isochrone dating on biotite from prograde and retrograde skarn gives133±6Ma and128±2Ma, respectively. They are contemporary with the monzonite porphyry (LA-ICP-MS zircon U-Pb age of126-128Ma) and Granite porphyry(LA-ICP-MS zircon U-Pb age of127Ma,133Ma). The zircon SHRIMP U-Pb dating of diorite from the Tongjing gold district in Yinan Country has yield concordant ages of128±3Ma, with which we reach the conclusion that the Tongjing gold deposit was formed at around128Ma. The single grain pyrite Rb-Sr dating of the Qibaoshan gold deposit give an average isochron age of117Ma±, which are later about7Ma than the Quartz diorite porphyry (K-Ar age of124.1Ma). These ages of ore-forming and magmatism provide the time constraints for the genetic relationship between the gold metallogeny and magmatic evolution in the Yishu fault zone and adjacent area.(4) The calculated δD and δ18O using measurements of fluid in inclusion waters extracted from auriferous quartz of Longquanzhan gold deposit is-77%o and3.97%o to4.07%o. the fluid inclusions from the Au and Cu mineralization stage of Qibaoshan gold deposit have δDH2O of-78.6‰-48.14%o and δ18Omo of+3.05‰-+5.77%o, and calculated δDH2O and δ18O values of fluid inclusion from quartz range from the quartz-sulfide stage of Tongjing gold deposit is-87%o and-0.4%o. The fluids of quartz from the above gold deposits are nearly similar to magmatic water and consistent with a predominance of magmatic fluids in the ore system. In addition, the δD and818O values of the carbonation stage fluid, extracted from fluid inclusions in calcite, plot towards the meteoric water line. This indicates the latter fluids likely had a high meteoric component.The3He/4He ratios in inclusion fluids of the Longquanzhan gold deposit are0.14Ra to0.78Ra with an average of0.39Ra. The40Ar/36Ar ratios are482-1811, averaging957, obviously higher than that of air (295.5), and the40Ar*/4He ratios of0.078-0.272. The3He/4He ratios of Yinan gold deposit vary from0.11Ra to1.02Ra. The40Ar/36Ar ratios are in the range of364-458with40Ar*/He ratios of0.154-0.735. The3He/4He ratios of Qibaoshan gold deposit vary from0.187Ra to0.194Ra, and40Ar/36Ar of291-842with40Ar*/4He of0-0.04. The elevated3He/4He ratios indicate a mantle-derived component in the ore fluids, and the percentage of mantle-derived He can be calculated according to the crust-mantle mixing model. The percentage of mantle helium involved in the ore-forming fluids trapped within the pyrite grains from gold deposits of the six metallogenic belts were calculated with the equation mentioned above. The results show1.63%to9.66%(average4.72%) mantle helium involved in the Longquanzhan gold mineralization. They are similar to Yinan gold deposit (1.29-12.60%, average5.09%), and higher than those of Qibaoshan gold deposit (2.21-2.30%, average2.26%). However, they are obviously lower than those of Zhaoyuan-Laizhou-Pingdu metallogenic belt and Mouping-Rushan metallogenic belt. The radiogenic Ar isotope compositions is present in ore-forming fluids and the caculated proportion of Longquanzhan gold deposit is38.7%-83.7%, Tongjing gold deposit of18.8%-35.5%and Qibaoshan gold deposit of0-64.9%. These results indicate that the ore-forming fluid was a mixture of mantle fluid, crustal magmatic fluid and MSAW. The occurrence of a mantle component in ore-forming fluid indicates the gold mineralization, including Tongjing, Longquanzhan and Qibaoshan was the result of crust and mantle interaction. However, the proportion of the mantle He of the Longquanzhan and Yinan gold deposit is a little higher than the Qibaoshan gold deposit, and more air-saturated water participate in the Yinan and Qibaoshan gold deposit. δ34S values of the Tongjing, Longquanzhan and Qibaoshan gold deposits range from0.9%o to4.4%o,1.53%o to5.6%o and0.3%o to5.89%o, respectively, similar to magmatic sulphur.3sulfide samples from the Longquanzhan gold deposit have206Pb/204Pb=15.779-19.037,207Pb/204Pb=15.076-15.643,208Pb/204Pb=36.744-40.488. three wallrock samples have206Pb/204Pb,207Pb/204Pb and208Pb/204Pb calculated using the time (96Ma) of hydrothermal deposition of pyrite, were15.40-17.754,15.053-15.472and35.734-37.801, Ores from the Longquanzhan gold deposit have distinct Pb isotopic compositions to age-corrected data of wallrock and probably indicate that the ore-forming metals were sourced from a crustally-derived magma. This view is also consistent with interpretation of the He-Ar isotope data.10sulfide from the Tongjing gold deposit have206Pb/204Pb=19.04-23.08,207Pb/204Pb=15.69-16.30and208Pb/204Pb=38.40-41.46, they are rich in U-radiogenic Pb and Th-radiogenic Pb. The calculated206Pb/204Pb,207Pb/204Pb and208Pb/204Pb using the time (130Ma) of hydrothermal deposition of molybdenite of2diorite porphyry samples are17.855-17.956,15.505-15.528and37.826-37.883, which are significantly lower than the Pb compositions of sulfide in Tongjing gold deposit, but they share the same linear relationship in the207Pb/204Pb and208Pb/204Pb versus206Pb/204Pb diagram. These isotopic compositions confirm a genetic relationship between the gold mineralization and magmatism and indicate the Pb isotopic compositions of sulfide are probably derived from the lower crust, mantle and sediment strata source.7sulfide samples from Qibaoshan gold deposit have206Pb/204Pb=16.624-17.725,207Pb/204Pb=15.238-15.512,208Pb/204Pb=36.414-37.721, Ores from Qibaoshan gold deposit have similar Pb isotopic compositions to the Pb isotopic data of volcano-subvolcanic rocks(206Pb/204Pb=16.485-17.056,207Pb/204Pb=15.149-15.388,208Pb/204Pb=36.445-37.484), combing with H-O, He-Ar isotopic data, we conclude that these provide multiple constraints for the genetic relationship between the gold mineralization and magmatism.(5) we integrate high-quality radiometric ages of gold mineralization in the study area which are reported in recent years. These results show that two gold metallogeny episodes can be identified, the Early Cretaceous gold metallogeny are related with those of enriched mantle-derived high-K calc-alkaline series, Most important, the ore fluid and metals also derived from the Early Cretaceous and Late Cretaceous (?) magmatism, in combination with these results described above, this paper presents a genetic model of Early Cretaceous skarn gold deposit+cryptoexplosion breccia pipe Au-Cu polymetallic deposit and Late Cretaceous altered rock type gold deposit.更多还原