内蒙古乌日尼图花岗岩的年代学、地球化学及其地质意义

乌日尼图隐伏岩体位于内蒙古自治区苏尼特左旗查干敖包镇西北乌日尼图地区,主要岩石类型为细粒-中细粒花岗岩、二长花岗岩。岩相学及地球化学特征研究表明,乌日尼图花岗岩体属于高钾钙碱性岩系,SiO₂含量为74.85%～78.10%,K₂O/Na₂O比值介于1.45～3.08之间,铝指数A/CNK=1.00～1.21,属过铝质岩石。主微量稀土元素分析表明,该岩体富集Rb、Th、U等元素而Ba、Nb、Sr、P和Ti强烈亏损,Eu为负异常(δEu= 0.22～0.39),总体呈现轻稀土富集的右倾“V”形分布配分模式。LA-ICP-MS锆石U-Pb定年表明,乌日尼图花岗岩体形成于早白垩世(139 Ma),为燕山运动晚期的产物。乌日尼图花岗岩体属A型花岗岩,形成于伸展的大地构造环境,且源区成分不均一,源岩可能主要由富黏土的泥质岩夹杂少量砂屑岩变质形成。     

内蒙古苏尼特左旗乌日尼图钨钼矿床同位素地球化学特征

乌日尼图钨钼矿位于内蒙古苏尼特左旗境内,是近几年在该区新发现较大规模的钨钼矿床。钨钼矿体主要产于燕山期花岗岩体的内外接触带附近,以细脉状矿化类型为主。同位素测试结果表明:δ34SV-CDT值范围为0.6‰～4.1‰,组成较为稳定;显示钨钼矿体的形成与岩浆作用密切相关,硫可能主要来自岩浆源。矿石样品208Pb/204Pb值范围为38.115～38.353,207Pb/204Pb值范围为15.528～15.591,206Pb/204Pb值范围为18.375～18.528;铅构造模式图解和其参数综合分析表明成矿与岩浆作用密切相关,成矿物质来源于上地壳与地幔的混合,具有壳幔混合特点。热液方解石δ13CPDB=-8.63‰～-6.41‰,δ18OSMOW=-1.49‰～8.72‰,表明热液矿物方解石是2个阶段成矿作用的产物,早期成矿流体碳主要来源于岩浆;成矿作用后期有大气降水的加入。     

Geochemistry and Sr-Nd-Pb Isotopes of the Granites from the Hashitu Mo Deposit of Inner Mongolia, China: Constraints on Their Origin and Tectonic Setting

The Hashitu molybdenum deposit is located in the southern part of the Great Hinggan Range,NE China.Molybdenum mineralization is hosted by and genetically associated with monzogranite and porphyritic syenogranite.Sr-Nd-Pb isotopes of the intrusions show that the porphyritic syenogranite has initial~(87)Sr/~(86)Sr ratios of 0.70418-0.70952,ε_(Nd)(t)values of 1.3 to 2.1(t=143Ma),~(206)Pb/~(204)Pb ratios of 19.191-19.573,~(207)Pb/~(204)Pb ratios of 15.551-15.572,and~(208)Pb/~(204)Pb ratios of38.826-39.143.The monzogranite has initial~(87)Sr/~(86)Sr ratios of 0.70293-0.71305,ε_(Nd)(t)values of 1.1 to2.0(t=147 Ma),~(206)Pb/~(204)Pb ratios of 19.507-20.075,~(207)Pb/~(204)Pb ratios of 15.564-15.596,and~(208)Pb/~(204)Pb ratios of 39.012-39.599.The calculated Nd model ages(T_(DM))for monzogranite and porphyritic syenogranite range from 866 to 1121 Ma and 795 to 1020 Ma,respectively.The granitic rocks in the Hashitu area have the same isotope range as granites in the southern parts of the Great Hinggan Range.The isotope composition indicates that these granites are derived from the partial melting of a juvenile lower crust originating from a depleted mantle with minor contamination by ancient continental crust.The integrating our results with published data and the Late Mesozoic regional tectonic setting of the region suggest that the granites in the Hashitu area formed in an intra-continent extensional setting,and they are related to the thinning of the thickened lithosphere and upwelling of the asthenosphere.     

内蒙古锡林浩特东部地区早白垩世花岗岩地球化学、锆石U Pb年龄及地质意义

通过对锡林浩特东部地区早白垩世花岗岩体进行SHRIMP锆石U Pb测年、地球化学测试,讨论其形成构造环境。花岗岩测年结果为：正长花岗岩(DS214)(1391±17) Ma,花岗岩(DS220)(1347±17) Ma,表明研究区花岗岩形成于早白垩世早期。花岗岩地球化学具有高硅、富碱、相对低铝的特征,A/CNK平均值106,为弱过铝质花岗岩。微量元素相对富集大离子亲石元素(Th、U、K),明显亏损Nb、Ba、Sr、P、Ti等高场强元素;稀土总量高,为12290×10-6～36877×10-6,LREE/HREE值为571～1436,呈右倾模式,负Eu异常显著(010～050),表现为A型花岗岩特征。K2O-Na2O构造环境判别图表明样品为A型花岗岩,Y/Nb Ce/Nb图解显示花岗岩为A2型。主量元素、微量元素特征指示花岗岩形成于造山后岩石圈伸展作用阶段,在壳源岩浆演化过程中存在幔源物质混染作用。花岗岩成因可能是晚古生代末—中生代初期间古亚洲洋闭合引起的一系列板块碰撞作用(包括蒙古—鄂霍次克洋闭合),使造山后期地壳逐渐增厚并发生重力垮塌,导致构造环境由挤压转变为伸展,同时受古太平洋板块西向俯冲的影响。     

Zircon U–Pb Dating and Geochemistry of the Linong Granitoid and Its Relationship to Cu Mineralization in the Yangla Copper Deposit,Yunnan, China

The Yangla copper deposit (Cu reserves: 1.2 Mt) in the Jinshajiang–Lancangjiang–Nujiang region in China is spatially associated with the Linong granitoid. Zircon U–Pb dating shows the granitoid formed at 234.1 ± 1.2 to 235.6 ± 1.2 Ma, and the KT2 ore body of the deposit yields a molybdenite Re–Os model age of 230.9 ± 3.2 Ma. The ages of mineralization and crystallization of the granitoid are identical within the measurement uncertainties, suggesting the Yangla deposit is genitically related to the Indosinian Linong granitoid.     

LA-ICP-MS Zircon U-Pb Geochronology of the Fine-grained Granite and Molybdenite?Re-Os?Dating in the Wurinitu Molybdenum Deposit, Inner Mongolia, China

The Wurinitu molybdenum deposit, located in Honggor, Sonid Left Banner of Inner Mongolia, China, is recently discovered and is considered to be associated with a concealed fine-grained granite impregnated with molybdenite.?The wall rocks are composed of Variscan porphyritic-like biotite granite and the Lower Ordovician Wubin’aobao Formation.?LA-ICP-MS zircon U-Pb dating of the fine-grained granite reveals two stages of zircons,?one were formed at 181.7±7.?4 Ma and?the other at 133.6±3.3 Ma. The latter age is believed to be the formation age of the fine-grained granite, while the former may reflect the age of inherited zircons, based on the morphological study of the zircon and regional geological setting. The Re-Os model age of molybdenite is 142.2±2.5?Ma, which is older than the diagenetic age of the fine-grained granite.?Therefore the authors believe that the metallogenic age of the Wurinitu molybdenum deposit should be?nearly 133.6±3.3 Ma or slightly later, i.e., Early Cretaceous.?Combined with regional geological background research, it is speculated that the molybdenum deposits were formed at the late Yanshanian orogenic cycle in the Hingganling-Mongolian orogenic belt, belonging to the relaxation epoch posterior to the compression and was associated with the closure of the Mongolia-Okhotsk?Sea.     

Late Triassic Biotite Monzogranite from the Western Litang Area,Yidun Terrane,SW China: Petrogenesis and Tectonic Implications

The Late Triassic igneous rocks in the Yidun terrane can provide vital insights into the evolution of Plaeo-Tethys in western China. We present new zircon U-Pb, whole-rock geochemistry, and Sr-Nd-Pb-Hf isotopic data for the Litang biotite monzogranites, Yidun terrane. The biotite monzogranites have a zircon U-Pb age of 206.1±1.0 Ma(MSWD=1.9,n=30), which indicates Late Triassic magmatism. The biotite monzogranites display I-type affinity, high Na_2O(3.38-3.60 wt%) contente,medii SiO_2(67.12-69.13 wt%), and low P_2 O_5 contents(0.10～0.12 wt%). They enriched in Rb,and Ba and depleted in Nb and Ta, with negative Eu anomalies(Eu/Eu*=0.74—0.81). They have evolved Sr-Nd-Pb-Hf isotopic composition, i.e.,(~(87) Sr/~(86 )Sr)i=0.714225 to 0.714763, negative ?_(Nd(t)) values of -2.0 to-2.6 with two-stage Nd model ages ranging from 1.01 to 1.05 Ga, negative ?_(Ht)(t)) values o f-3.4 to-4.1 with two-stage Hf model ages of 1.85 to1.88 Ga, suggesting a matured crustal sources. Their low Al_2O_3/TiO_2 ratios and medium Cao/Na_2O ratios, medium Mg~# and SiO_2 contents, low [molar Al_2O_3/(MgO+FeO~T)] values, and high [molar Cao/(MgO+FeO~T)] values indicate that the Litang biotite monzogranite was formed by partial melting of metabasaltic rocks. Based on the previous studies, we propose that the Litang biotite monzogranite derived from the westward subduction and closure of the Ganzi-Litang ocean during the Late Triassic-The mantle wedge-derived mafic melts provided sufficient heat for partial melting of ancient metabasalt protolith within the middle-lower crust.     

辽宁海城地区老虎沟基性岩墙锆石UPbHf同位素、地球化学特征及其地质意义

胶-辽-吉活动带是华北板块重要的古元古代造山带,与南北两侧的狼林地块和龙岗地块通过断层接触,共同构成了东部陆块。造山带内分布有大量的变沉积岩系,并在多期岩浆-变质事件的改造下,经历了十分复杂的构造演化过程。其中,在辽宁海城—草河口地区分布着大量古元古代变质基性岩墙,分别为北东—南西走向的什司县基性岩墙群和北西—南东走向的老虎沟基性岩墙群。什司县基性岩墙与北辽河群中的浪子山岩组和里尔峪岩组呈互层状产出于胶-辽-吉带内,老虎沟基性岩墙高角度侵入到龙岗地块东南缘新太古宙片麻岩中。LA-ICPMS锆石U-Pb-Hf同位素测试结果显示老虎沟基性岩经历（1 864±15）Ma的变质作用,锆石Hf同位素一阶段模式年龄（TDM1）为2 040~2 293Ma,代表了老虎沟基性岩从地幔中抽取出来的时间。以上测试结果与辽阳地区什司县基性岩年代学记录和Hf同位素数据一致。主、微量元素地球化学分析结果亦表明,老虎沟基性岩墙与什司县基性岩墙的地化特征基本一致,均具有右倾型的稀土配分模式,选择性富集大离子亲石元素和亏损高场强元素,暗示两者形成于相似的构造环境。在Nb/Yb-Th/Yb图解中,老虎沟基性岩和什司县基性岩样品均具有Th的强烈富集,指示了俯冲作用的存在。但是老虎沟基性岩具有相对较高的Nb/Zr值,说明其源区经历过硅酸盐熔体的交代富集作用,而什司县基性岩低的Nb/Zr和变化较大的Th/Zr值指示其源区受到了流体的交代作用。综上分析,老虎沟基性岩和什司县基性岩形成于同一构造背景,二者源区分别受到了硅酸质熔浆和流体的交代作用,随后受1 930~1 850Ma的俯冲碰撞造山作用的影响发生了变质。     

中天山天湖东铁钼矿含矿片麻状花岗岩年代学、地球化学和锆石Hf同位素-对于中天山早古生代构造演化的启示

以中天山东段的天湖东铁钼矿含矿花岗岩为例,在LA-ICP-MS锆石U-Pb年代学测定其为早古生代花岗岩（（445.3±4.6） Ma）基础上,通过岩相学、地球化学及锆石原位Hf同位素组成等多方面研究,探讨该岩体的成岩作用及其构造背景。天湖东含矿片麻状花岗岩的主要矿物为斜长石、石英、钾长石,并含少量黑云母和角闪石等。全岩地球化学分析结果表明,该片麻状花岗岩高硅、弱富铝、富钙、富钠而贫钾,ASI值为0.68~0.82,属于准铝质钙碱性花岗岩,总体上富集大离子亲石元素（LILE）Rb、Ba等和轻稀土元素La、Ce、Nd等,而亏损高场强元素Nb、Ta、Ti、Yb等,轻重稀土分异明显,轻稀土分异较为明显,而重稀土分异不明显,表现出典型岛弧岩浆岩的地球化学特征。锆石的ε_Hf(445 Ma)值为-6.31~-1.77,二阶段Hf模式年龄（T_DM2）为1.538~1.825 Ga,表明该花岗岩的源区主要为壳源物质。综合分析上述资料,认为天湖东铁钼矿片麻状花岗岩是由俯冲过程中地壳物质重熔的产物。结合前人的研究和本课题组的新近研究成果认为,在早古生代时,中天山为岩浆弧构造环境,形成一系列的钙碱性岩浆岩,而该岩浆弧的形成可能是受到介于吐哈陆块和塔里木板块之间的古天山大洋在早古生代时期向南俯冲而形成的。     

海南加茂地区红峰队岩体锆石U-Pb年代学、Hf同位素及其对构造环境的指示

本文在野外地质调查的基础上,对海南加茂地区红峰队细中粒黑云母正长花岗岩体进行锆石年代学、Hf同位素及地球化学等特征的深入研究,以揭示该岩体形成的构造环境。结果显示,红峰队花岗岩体锆石LA-ICP-MS U-Pb年龄为259.5±1.3 Ma,形成于晚二叠世;具有高硅（SiO2=72.26%～75.69%）、富碱（K2O+Na2O=8.51%～9.18%）,高钾（K2O/Na2O=1.13～1.7）,贫CaO（0.38%～0.75%）和P2O5（0.01%～0.02%）等地球化学特征,A/CNK值为0.99～1.08,属于准铝质-弱过铝质花岗岩;富集Rb、Th、U、K、Pb、Nd、Zr、Hf、Sm和轻稀土,明显亏损Ba、Nb、Ta、Sr、P、Eu、Ti,具强烈的负Eu异常;锆石饱和温度也较低（767～796℃）;显示该岩体属于高分异I型花岗岩;εHf(t)值变化较小（+3.0 ~ +7.3）,反映了其岩浆来源较为均一。红峰队岩体来源于新生地壳的部分熔融,并且发生了较高程度的分离结晶,可能形成于华南与印支块体的碰撞后伸展环境。     

内蒙古锡林浩特毛登牧场早石炭世花岗岩锆石U Pb年龄、地球化学特征及其地质意义

通过对内蒙古锡林浩特毛登牧场早石炭世花岗岩体进行野外观察、LA ICP MS锆石U Pb测年以及地球化学测试,讨论其构造环境,进一步为研究古亚洲洋闭合时限提供依据。测年结果表明：花岗闪长岩为(3306±18) Ma,二长花岗岩为(3277±26) Ma,成岩时代为早石炭世。岩石地球化学分析表明:花岗闪长岩为强过铝质、钙碱性系列岩石,具有活动大陆边缘的亲缘性特征。微量元素特征指示花岗闪长岩具有典型下地壳来源特征并伴有部分幔源岩浆混合作用,为弧岩浆岩。二长花岗岩为具高硅、富碱、相对低铝特征的高钾钙碱性系列岩石。两类差异明显的岩石稀土配分曲线表明二长花岗岩具有下地壳岩浆重熔的演化特征。微量元素特征指示样品为大陆弧环境下壳源重熔的成熟弧花岗岩。构造判别图显示花岗闪长岩为代表活动大陆边缘环境的I型花岗岩,而二长花岗岩则为指示活动大陆边缘弧后伸展环境的A2型花岗岩,二者构成I－A型复合岩体,说明研究区在早石炭世仍存在古亚洲洋向西伯利亚板块的俯冲作用,推测古亚洲洋此时尚未闭合。     

Emplacement Ages and Petrogenesis of the Molybdenum–bearing Granites in the Jinduicheng Area of East Qinling, China: Constraints from Zircon U–Pb Ages and Hf Isotopes

The Mesozoic porphyry assemblage in the Jinduicheng area is a special molybdenum area in China, the Mo deposits, including the Jinduicheng, Balipo, Shijiawan, Huanglongpu, are distributed. The emplacement age and geochemical features of the granites in the Jinduicheng area can provide essential information for the exploration and development of the porphyry molybdenum deposit. In this study, we report LA–ICP–MS zircon U–Pb age and zircon Hf isotopic compositions of granite porphyries from the Jinduicheng area, and provide insights on the petrogensis and source characteristics of the granites. The results show that the zircon U–Pb ages of the Jinduicheng granite porphyry (143±1 Ma) and the Balipo granite (154±1 Ma), agree well with the Re–Os ages of molybdenite in the Jinduicheng molybdenum polymetallic deposit (139±3 Ma) and the Balipo molybdenum polymetallic deposit (156±2 Ma), indicating that the emplacement of granite porphyries occurred between Late Jurassic and Early Cretaceous. Zircons granite from the Jinduicheng area give the εHf(t) values mainly ranging from ?10 to ?16, and ?20 to ?24, respectively, corresponding to two–stage model ages (tDM2: mainly focused on 1.86–2.0 Ga, and 2.2–2.6 Ga, respectively) of zircons of the granite from the Jinduicheng values. The ore–forming materials are mainly derived from crust, with minor mantle substances. Zircons of the granite from the Balipo area give εHf(t) values ranging from ?18 to ?20, ?28 to ?38, and ?42 to ?44, respectively, corresponding to two–stage model ages (tDM2: mainly focused on 1.88–3.0 Ga, and 3.2–3.90 Ga, respectively). the εHf(t) values of the Jinduicheng porphyry more than that of the Balipo porphyry, and two–stage model ages (tDM2) less than that of the Balipo porphyry, shows that he source of the porphyries originated from ancient lower crustal materials in the Jinduicheng area, and mixed younger components, more younger components contributed for the source of the Jinduicheng porphyry.     

Age and Tectonic Setting of Mesothermal Magmatic Hydrothermal Vein‐Type Pb–Zn–(Ag) Mineralization in the Xiaohongshilazi Deposit,Central Jilin Province,Northeast China

The Xiaohongshilazi deposit located in central Jilin Province, Northeast China, is a newly discovered and medium‐scale Pb–Zn–(Ag) deposit with ore reserves of 34,968 t Pb, 100,150 t Zn, and 158 t Ag. Two‐stage mineralization has been identified in this deposit. Stratiform volcanic‐associated massive sulfide (VMS) Pb–Zn mineralization interbedding with the marine volcanic rocks of the Late Carboniferous–Early Permian Daheshen Formation was controlled by the premineralization E–W‐trending faults. Vein‐type Pb–Zn–(Ag) mineralization occurs within or parallel to the granodiorite and diorite porphyries controlled by the major‐mineralization N–S‐trending faults that cut the stratiform mineralization and volcanic rocks. To constrain the age of vein‐type Pb–Zn–(Ag) mineralization and determine the relationship between mineralization and magmatism, we conducted LA–ICP–MS U–Pb dating on zircon from the ore‐bearing granodiorite and diorite porphyries and Rb–Sr dating on metal sulfide. Granodiorite and diorite porphyries yield zircon U–Pb weighted‐mean ²⁰⁶Pb/²³⁸U ages of 203.6 ± 1.8 Ma (Mean Standard Weighted Deviation [MSWD] = 1.8) and 225.6 ± 5.1 Ma (MSWD = 2.3), respectively. Sulfides from four vein‐type ore samples yield a Rb–Sr isochron age of 195 ± 17 Ma (MSWD = 4.0). These results indicate a temporal relationship between the granodiorite porphyry and vein‐type Pb–Zn–(Ag) mineralization. The granodiorite associated with vein‐type mineralization has high SiO₂ (68.99–70.49 wt.%) and Na₂O (3.9–4.2 wt.%; Na₂O/K₂O = 1.07–1.10) concentrations, and A/CNK values of 0.95–1.04; consequently, the intrusion is classified as a high‐K, calc‐alkaline, metaluminous I‐type granite. The granodiorite porphyry is enriched in large‐ion lithophile elements (e.g. Rb, Th, U, and K) and light REE and is depleted in high‐field‐strength elements (e.g. Nb, Ta, P, and Ti) and heavy REE, indicating that it represents a subduction‐related rock that formed at an active continental margin. Furthermore, the granodiorite porphyry has Mg# values of 31–34, indicating a lower crustal source. Based on petrological and geochemical features, we infer that the ore‐bearing granodiorite porphyry was derived from the partial melting of the lower crust. In summary, mineralization characteristics, cross‐cutting relationships, geochronological data, and regional tectonic evolution indicate that the region was the site of VMS Pb–Zn mineralization that produced stratiform orebodies within the Late Carboniferous–Early Permian marine volcanic rocks of the Daheshen Formation, followed by mesothermal magmatic hydrothermal vein‐type Pb–Zn–(Ag) mineralization associated with granodiorite porphyry induced by the initial subduction of the Paleo‐Pacific Plate beneath the Eurasia Plate during the Late Triassic–Early Jurassic.     

Geology and Geochemistry of the Shizitou Molybdenum Deposit,Jiangxi Province: Implications for Geodynamic Setting and Metallogenesis

The Shizitou molybdenum(Mo) deposit in Yongping, Jiangxi, is an important, recently discovered deposit in the eastern section of the Qin–Hang metallogenic belt. The Mo deposit is located in the outer contact zone between the porphyritic biotite granite and the Neoproterozoic migmatite, and present in the deep central part of the intrusion. Re–Os dating and S and Pb isotopic analysis have been conducted to assess the metallogenesis of the Shizitou Mo deposit. S, Pb and Re isotopes show that the ore–forming materials were derived from the porphyritic biotite granitic magma, which originated from the mixing of mantle and crust. Re–Os dating of molybdenite from the ores gives a model age from 156.9±2.2 to 158.5±2.4 Ma, with a weighted mean age of 158±1 Ma and an isochron age of 158.0±2.5 Ma. Geological and geochemical characteristics of the ore deposit and the related granitoids indicate that the Shizitou deposit is a Climax–type Mo deposit. Based on previous studies of the Qin–Hang metallogenic belt, two metallogenic events are believed to have occurred during 172–145 Ma and 137–132 Ma. These two metallogenic periods are consistent with the timing of two metallogenic peaks during the middle to late Jurassic and the Cretaceous in South China. These events represent responses to the partial back–arc extension associated with the subduction of the Izanagi plate beneath the Eurasian continent and the rapid northeastward movement of the subducting Izanagi plate.     

Geology and Mineralization at the Dajing Tin-polymetallic Ore Deposit, Inner Mongolia, China

Abstract: Dajing is a large-scale tin–polymetallic ore deposit in north China with Sn, Cu, Pb, Zn, Ag, and minor elements such as Co and In. The deposit is controlled by a passage-host structure system. Two groups of NE direction faults such as F₂ and F₁ are characterized by sinistral and multiphase activities, and the syn-ore NE faults with their derivative faults nearly in N-S direction constitute an important structure system as channelway for ore fluid. Around F₂ fault (mineralization center), metallic elements display horizontal zoning outwards from Sn, Cu to Cu, Sn, Pb, Zn, Ag and to Pb, Zn, Ag. Controlled by sinistral pull-apart vein system, the WNW direction host structure yielded the ore vein to "W" shape on horizontal plan while to staircase shape on vertical profile. Multiperiodic activities of the host structures system lead to multistage of ore mineralization. Four mineralization stages are recognized in the main mineralization, i.e. 1) cassiterite–arsenopyrite–quartz stage, 2) cassiterite-sulfide (or Cu–poly–metallic mineralization) stage, 3) massive pyrite stage, and 4) galena-sphalerite stage. Besides, fluid activities are identified here at the pre-mineral stage of the formation of quartz veins and sheared deformation, and at the post-mineral stage of quartz–calcite–fluorite deposition.
The earlier tin-rich ore solution raised from NE faults and its nearly N-S derivatives filled the NW-WNW direction fractures, and formed tin ore veins. Subsequent mineralization of Cu-polymetallic stage, pyrite stage and galena-sphalerite stage, overlapping on the same fracture system, sequentially expanded outwards from the fractures, and produced different kinds of ore types and mineralization zoning.     

西昆仑沙子沟铜矿区花岗闪长岩年代学、地球化学及Hf同位素特征

沙子沟铜矿床位于西昆仑造山带西段,矿区内发育与成矿关系密切的花岗闪长岩体。笔者针对该岩体开展了岩石地球化学、锆石U-Pb年代学及Lu-Hf同位素组成的研究。LA-ICP-MS锆石U-Pb测年结果为（213.7±2.6）Ma,为锆石结晶年龄,属于晚三叠世;锆石Hf同位素组成表明εHf（t）值为-2.72~1.21,显示成岩过程中有少量幔源岩浆的参与;岩石地球化学结果表明花岗闪长岩具有富钙、富钾、富镁、富铁的特征,铝饱和指数A/CNK为0.99~1.04（<1.1）,具有中等强度的负Eu异常（δEu为0.54~0.94,平均为0.79）,富集Rb、Th、K、Nd、Sm和LREE等大离子亲石元素,亏损Ba、Nb、Ta、Sr、P、Ti和HREE等高场强元素,显示了I型花岗岩的特征。沙子沟铜矿床成因为岩浆热液型,其早期成矿时代与沙子沟花岗闪长岩形成时代吻合,成矿物质主要来自造山带下地壳,矿区弱过铝质I型花岗岩为成矿提供物源和热源。笔者认为沙子沟花岗闪长岩构造背景属古特提斯洋俯冲碰撞造山作用之后的后碰撞伸展构造,源岩可能由地幔底侵古老陆壳,是壳源花岗质岩浆与幔源基性岩浆发生强烈混合作用的产物,正是这种壳幔物质交换为区内铜多金属矿化提供大量成矿物质来源。     

黑龙江省四平山金矿床成矿作用及矿床成因：来自矿床地质、地球化学、锆石U-Pb年代学及H-O-S同位素的制约

四平山金矿床位于我国黑龙江省东部的完达山陆缘增生带内,矿体主要赋存于下白垩统四平山组,表现出明显的两阶段成矿作用特征。为进一步确定四平山金矿床的成矿作用及矿床成因,本次研究对其成矿地质特征、地球化学、成矿年代学及成矿物质来源进行了分析。地球化学分析结果表明：成矿花岗斑岩为具有高SiO₂（70.07%~72.93%）、（K₂O+Na₂O）（7.17%~8.42%）质量分数和右倾“海鸥型”稀土配分型式特征的A型花岗岩;含矿层状硅质岩中,Al/（Fe+Al+Mn）<0.32、Fe/Ti >20、(Fe+Mn)/Ti>20,并具有较高Fe₂O₃（0.18%～1.79%）、FeO（0.17%～0.96%）、MnO（0.03%~0.12%）、TiO₂（0.03%~0.04%）、Al₂O₃（0.30%~2.79%）和（K₂O+Na₂O）（0.07%~1.76%）质量分数,指示四平山金矿床形成于活动大陆边缘构造背景下与岩浆活动有关的热水沉积环境。四平山金矿床成矿花岗斑岩锆石U-Pb年龄为（113.5±0.7）Ma。H、O、S同位素分析结果（δD=-182.3‰~-84.0‰、δ¹⁸O_V-SMOW=6.5‰~14.3‰、δ³⁴S=-12.4‰~29.7‰）显示,成矿流体主要为大气降水,成矿物质具有以地层为主的多来源特征。综上,四平山金矿床为形成于燕山晚期活动大陆边缘构造背景下的热水沉积型矿床,太平洋板块持续俯冲造成了区域上大规模的拆沉作用,导致区域构造背景由挤压向伸展发生转换,此时形成的花岗斑岩岩浆运移至地壳浅部岩浆房加热上覆地层,在地壳浅部形成了温度与压力梯度带,促使地表的大气降水沿裂隙进入地层后形成流体循环系统,并不断萃取地层中的Au元素形成含矿流体。在成矿早阶段,当压力驱动含矿流体喷出地表后与地表水相遇快速冷却,成矿物质快速沉淀,形成含矿层状硅质岩和硅质胶结砾岩,并通过交代下伏流纹斑岩形成层状、似层状矿体;在成矿晚阶段,随着岩浆房提供的热动力减弱,含矿流体滞留在裂隙通道中或穿切进入早期固结的含矿层裂隙中,沉淀形成脉状-网脉状矿体。     

Geochronology and Geochemistry of the Early Permian A‐type Granite in the Hongol Area,Central Inner Mongolia: Petrogenesis and Tectonic Implications

We performed geochronological and geochemical analyses of the A-type granite in the Hongol area, central Inner Mongolia, to determine its age, petrogenesis and tectonic setting, which are significant for clarifying the Late Paleozoic tectonic evolution of the Xing'an Mongolian Orogenic Belt(XMOB). The rock type of the A-type granite in the Hongol area is alkali-feldspar granite, and it constitutes a western part of the Baiyinwula-Dongujimqin A-type granite belt. Zircon U-Pb geochronology yields ~(206)Pb/~(238)U ages ranging from 293 to 286 Ma for the alkali-feldspar granite, indicating this granitic pluton formed in the Early Permian. The alkali-feldspar granite is high in silica(SiO_2=75.13 wt%-80.17 wt%), aluminum(Al_2 O_3=10.59 wt%-13.17 wt%) and alkali(Na_2 O+K_2 O=7.33 wt%-9.11 wt%), and low in MgO(0.08 wt%-0.39 wt%) and CaO(0.19 wt%-0.70 wt%). It is obviously enriched in LILEs such as Rb, Th and K,depleted in HFSEs such as Nb, Ti, La and Ce, with pronounced negative anomalies of Nb, Ti, P, Eu, Sr and Ba. Its Sr-Nd-Pb isotopic compositions show positive ε_(Nd)(t)(+0.72-+3.08), low T_(DM2)(805-997 Ma),and high radioactive Pb with(~(206)Pb/~(204)Pb)_i of 18.710-19.304,(~(207)Pb/~(204)Pb)_i of 15.557-15.604 and(~(208)Pb/~(204)Pb)_i of 37.887-38.330. Petrological characteristics and geochemical data suggest that the alkalifeldspar granite in the Hongol area belongs to aluminous A-type granite. This A-type granite formed in a post-collisional extensional setting and was generated by the partial melting of felsic rocks in the middlelower crust resulting from post-collisional slab breakoff. It is suggested that the Paleo-Asian Ocean was closed before the Permian in central Inner Mongolia.     

内蒙古大井矿床碳氧同位素组成及其成因意义

利用碳氧同位素组成可以很好地判别其形成的沉积环境.以内蒙古大井矿床为例,对该矿床16个菱铁矿样品进行碳、氧同位素分析,δ13CPDB变化范围为-1.8‰～-6.6‰,δ18OVPDB变化范围为-23.1‰～-17.3‰.根据矿物δ13C与δ18O值投影到δ13C-δ18O图解中,样品数据在图中的投点落入热水沉积区,说明其形成过程中具有热水沉积作用的发生.古温度可以通过T=16.998-4.52(δ18cO-δ18wO)+0.03(δ18cO-δ18wO)2计算,其形成时的温度平均值为117℃,比海底和湖底的温度要高得多,主要原因在于热水流体参与成矿.碳酸盐的成矿环境可以通过公式Z=2.048(δ13C+50)+0.498(δ18O+50)计算:Z值大于120,表示成矿环境为海水;如果Z值小于120,表示成矿环境为淡水或湖水.内蒙古大井矿床菱铁矿的Z值为100～114,结合区域地质背景,大井矿床形成的古环境为深水湖泊环境.通过对碳氧同位素的分析,结合成矿地质背景、矿床地质特征以及微量元素组成,认为在大井矿床成矿的早期阶段曾经发生过热液沉积作用,本次研究不仅有利于全面理解和认识大井矿床成矿过程的全貌,而且有益于对古湖相环境热液事件的探索.     

湖南七宝山铜多金属矿床石英斑岩时代与成因:锆石U-Pb定年及Hf同位素与稀土元素证据

湖南浏阳七宝山铜多金属矿床位于钦杭成矿带西段,是湘东北规模最大的铜多金属矿床。矿床的形成与区内的石英斑岩关系密切。石英斑岩内锆石具有岩浆锆石特征,LA-ICP-MS锆石U-Pb定年结果为155~153 Ma,代表其形成年龄,属晚侏罗世岩浆活动产物。岩浆锆石的~(176)Hf/~(177)Hf=0.282296~0.282603,εHf(t)=–12~–2.7,平均地壳模式年龄tDM2=1377~2056 Ma;锆石ΣREE=496~4162μg/g,(Yb/Nd)N=71.9~3133.8,HREE强烈富集,具有强烈Ce正异常(δCe=1.68~203.13)和强烈至中等Eu负异常(δEu=0.05~0.67),表明石英斑岩的岩浆源区具有明显壳源特征,来自于古元古代至中元古代地壳的部分熔融。结合岩石学研究,七宝山矿区石英斑岩的形成除了中下地壳冷家溪群或更古老的基底物质的部分熔融外,还有幔源组分加入,这一期岩浆与成矿作用与岩石圈拆离和软流圈物质上涌及随后的玄武岩底侵作用有关。