文章快速检索    
 
  中国地质 2020, Vol. 47 Issue (4): 1109-1126  
0
引用本文
江拓, 邱啸飞, 卢山松, 杨红梅, 邓新, 彭练红. 2020. 桐柏—大别造山带南缘七尖峰花岗岩成因:来自地球化学、锆石U-Pb年代学和Hf同位素的制约[J]. 中国地质, 47(4): 1109-1126.  
Jiang Tuo, Qiu Xiaofei, Lu Shansong, Yang Hongmei, Deng Xin, Peng Lianhong. 2020. Petrogenesis of the Qijianfeng granite in southern Tongbai-Dabie orogenic belt:Constraints from geochemistry, zircon U-Pb age and Hf isotope[J]. Geology in China, 47(4): 1109-1126. (in Chinese with English abstract).  

桐柏—大别造山带南缘七尖峰花岗岩成因:来自地球化学、锆石U-Pb年代学和Hf同位素的制约
江拓1,2,3, 邱啸飞1,2,3, 卢山松1,2,3, 杨红梅1,2,3, 邓新1,2, 彭练红1,2    
1. 中国地质调查局武汉地质调查中心, 湖北 武汉 430205;
2. 中南地质科技创新中心, 湖北 武汉 430205;
3. 中国地质调查局花岗岩成岩成矿地质研究中心, 湖北 武汉 430205
摘要:以桐柏—大别造山带南缘七尖峰花岗岩体为研究对象,进行了详细的同位素年代学和元素-同位素地球化学研究,对其岩石成因和桐柏—大别造山带南缘早白垩世构造背景与钼成矿作用进行了探讨。锆石LA-ICP-MS U-Pb定年结果表明,七尖峰花岗岩形成年龄为(140±1)Ma,说明其为早白垩世岩浆活动的产物。地球化学研究表明,七尖峰花岗岩具有高SiO2(72.88%~73.60%)、低MgO(0.33%~0.36%),高Sr(620×10-6~642×10-6)、Sr/Y(107~111)比值,低Y(5.65×10-6~5.95×10-6)、Yb(0.52×10-6~0.59×10-6)、无Eu负异常的地球化学特征,是典型的埃达克岩。岩体富K2O、贫Cr和Ni,具有富集的Sr-Nd同位素组成(ISr=0.7075~0.7078,εNdt)=-15.5~-15.1),锆石εHft)值在-19.9~-13.2变化,对应的两阶段Nd和Hf模式年龄分别介于2.15~2.19 Ga和2.00~2.43 Ga,暗示七尖峰花岗岩是由古老的加厚下地壳含石榴石角闪岩部分熔融形成。结合前人的研究成果,认为桐柏—大别造山带白垩纪存在两期与钼成矿密切相关的岩浆事件,早期(>130 Ma)与加厚下地壳部分熔融有关,晚期(< 130 Ma)则形成于非加厚地壳部分熔融,证明桐柏—大别造山带南缘早白垩世(约130 Ma)经历了从碰撞挤压地壳加厚到碰撞后伸展地壳减薄的构造垮塌演化过程。
关键词桐柏-大别造山带    七尖峰花岗岩    锆石U-Pb年龄    Hf同位素    埃达克岩    地质调查工程    矿产勘查工程    
中图分类号:P541            文献标志码:A             文章编号:1000-3657(2020)04-1109-18
Petrogenesis of the Qijianfeng granite in southern Tongbai-Dabie orogenic belt:Constraints from geochemistry, zircon U-Pb age and Hf isotope
JIANG Tuo1,2,3, QIU Xiaofei1,2,3, LU Shansong1,2,3, YANG Hongmei1,2,3, DENG Xin1,2, PENG Lianhong1,2    
1. Wuhan Center of China Geological Survey, Wuhan 430205, Hubei, China;
2. Central South China Innovation Center for Geosciences, Wuhan 430205, Hubei, China;
3. Research Center of Petrogenesis and Mineralization of Granitoid Rock, China Geological Survey, Wuhan 430205, Hubei, China
Abstract: Based on comprehensive geochronological, elemental and isotopic geochemical studies of the Qijianfeng granite in southern Tongbai-Dabie orogenic belt, the authors investigated the petrogenesis as well as the geodynamic settings and Mo mineralization of southern Tongbai-Dabie orogenic belt during Early Cretaceous. LA-ICP-MS zircon U-Pb dating yielded an age of (140±1) Ma for the Qijianfeng granite. The rocks exhibit adakitic characteristics, such as high SiO2 (72.88%-73.60%), low MgO (0.33%-0.36%), high Sr (620×10-6-642×10-6) content and high Sr/Y(107-111) ratios, low Y (5.65×10-6-5.95×10-6) and Yb (0.52×10-6-0.59×10-6) content, with negligible Eu anomalies. The rocks are enriched in K2O and depleted in Cr and Ni, and show enriched Sr-Nd isotopic compositions with initial 87Sr/86Sr and epsilon Nd(t) ranging from 0.7075 to 0.7078 and from -15.5 to -15.1, respectively. The rocks have zircon εHf(t) values of -19.9--13.2 with corresponding two-stage Nd and Hf model ages from 2.15 to 2.19 Ga and from 2.00 to 2.43 Ga respectively, suggesting that the magmas were derived from partial melting of ancient garnet-bearing amphibolites from the thickened lower crust. Combined with the previous studies, the authors propose two-stage magmatic activities and accompanying Mo mineralization during Early Cretaceous in southern Tongbai-Dabie orogenic belt. The first stage Mo-related rocks (>130 Ma) were derived from the partial melting of the thickened lower crust, while the second stage Mo-related rocks (< 130 Ma) were generated in a normal crustal environment. It is suggested that the southern Tongbai-Dabie orogenic belt experienced a tectonic transition from collisional compression to post-collisional extension, i.e., collapse, delamination and thinning of over-thickened orogenic crust and lithosphere during early Cretaceous (ca. 130 Ma).
Key words: Tongbai-Dabie orogenic belt    Qijianfeng granite    zircon U-Pb age    Hf isotope    adakite    geological survey engineering    mineral exploration engineering    

1 引言

秦岭—桐柏—大别—苏鲁造山带是扬子与华北板块之间的复合型碰撞造山带,不仅是目前世界上出露规模最大、保存最好的高压—超高压变质区之一,也是陆-陆碰撞后岩浆活动最为强烈的地区之一(张国伟等, 1996; 郑永飞, 2008Wu and Zheng, 2013; Dong and Santosh, 2016)。在深俯冲陆壳折返和碰撞后加厚造山带拉张垮塌过程中,可以形成大量的同折返和碰撞后岩浆岩,研究这些碰撞后岩浆岩的形成时代、岩石成因、物质来源及其形成的地球动力学背景,对认识俯冲大陆岩石圈再循环和碰撞造山带的构造演化具有十分重要的意义(赵子福等, 2009)。

大别造山带是中国一条重要的钼多金属成矿带,与东秦岭相连构成中国最大的钼成矿带,拥有钼资源储量超过8×106 t,占中国钼资源储量的66%(Mao et al., 2011Chen et al., 2017b)。目前大别山地区已相继发现多处钼矿床,自西向东依次有肖畈、母山、千鹅冲、宝安寨、大银尖、姚冲、汤家坪和沙坪沟等钼矿床(图 1),其中沙坪沟钼矿达到超大型规模,是仅次于美国Climax的世界第二大钼矿床,也是亚洲第一大钼矿(Mao et al., 2011)。研究表明,这些钼矿床绝大多数都是斑岩型矿床,与区内广泛分布的早白垩世花岗岩紧密相关(Chen et al., 2017b)。值得注意的是,截至目前已报道的钼矿多位于安徽和河南省内的大别山地区,而桐柏地区尤其是湖北省内发现的钼矿无论在数量上还是规模上,都明显不及大别山地区。最近,在湖北随县发现了黄家沟中型钼矿床(Chen et al., 2017a),同时在随州—枣阳七尖峰地区发现了一系列钼矿化围绕七尖峰花岗岩分布(谭超等, 2018)。研究表明,黄家沟钼矿含矿花岗岩成岩年龄为(137.6±1.6) Ma,辉钼矿Re-Os年龄为(137.0±8.1) Ma(Chen et al., 2017a),七尖峰岩体的年龄为141~133 Ma (Zhang et al., 2013; 陈超等, 2018),成岩时代与钼成矿时代近于同时,暗示这些钼矿(化)可能与七尖峰岩体存在一定关系(谭超等, 2018)。虽然前人对该岩体的形成时代、地球化学特征进行了部分研究,但缺乏该岩体与大别地区同时代岩浆岩,尤其是与钼成矿相关花岗岩的综合对比研究,制约了对桐柏地区早白垩世岩浆岩成因及钼成矿地球动力学背景的系统认识。

图 1 桐柏—大别造山带大地构造位置(a)和区域地质简图(b)(据Wang et al., 2014b修改) 1—沉积物(< 100 Ma);2—梅山群(石炭纪);3—信阳群(泥盆纪—三叠纪);4—苏家河群(0.85~0.43 Ga);5—随县群(新元古代);6—红安群(新元古代);7—大别/桐柏杂岩(>0.75 Ga);8—栾川群(新元古代早期);9—宽坪群(1.8~1.45 Ga);10—秦岭群(>0.43 Ga);11—二郎坪群(1.0~0.43 Ga);12—古生代花岗岩;13—古生代闪长岩;14—中生代花岗岩;15—中生代闪长岩-花岗闪长岩;16—中生代火山岩;17—采样点;18—断裂;19—大—超大型矿床;20—小—中型矿床;DWF—大悟断裂;SMF—商麻断裂;TSF—桐商断裂;XMF—晓天—磨子潭断裂;XTF—浠水—桐城断裂 Fig. 1 Schematic tectonic map (a) and simplified geological map (b) of the Tongbai-Dabie orogenic belt (modified from Wang et al., 2014b) 1-Sediments (< 100Ma); 2-Meishan Group (Carboniferous); 3-Xinyang Group (Devonian-Triassic); 4-Sujiahe Group (0.85-0.43Ga); 5-Suixian Group (Neoproterozoic); 6-Hong'an Group (Neoproterozoic); 7-Dabie/Tongbai complex (>0.75Ga); 8-Luanchuan Group (Early Neoproterozoic); 9-Kuanping Group (1.8-1.45Ga); 10-Qinling Group (>0.43Ga); 11-Erlangping Group (1.0-0.43 Ga); 12-Paleozoic granite; 13-Paleozoic diorite; 14-Mesozoic granite; 15-Mesozoic diorite-granodiorite; 16-Mesozoic volcanic rocks; 17-Sampling location; 18-Fault; 19-Large to giant deposit; 20-Small to medium deposit; DWF-Dawu Fault; SMF-Shangma Fault; TSF-Tongshang Fault; XMF-Xiaotian-Mozitan Fault; XTF-Xishui-Tongcheng Fault

本研究在详细的野外调查基础上,对桐柏造山带南缘七尖峰岩体进行了详细的锆石U-Pb年代学及Hf同位素、全岩主-微量元素和Sr-Nd同位素地球化学研究,精确限定了七尖峰花岗岩的侵位时代,详细探讨了其岩石成因及源区,并与桐柏—大别地区白垩纪与钼成矿密切相关的岩浆岩进行了系统对比,为探讨桐柏—大别造山带南缘早白垩世地球动力学背景及钼成矿作用提供了重要证据。

2 地质背景和岩石学特征

桐柏—大别造山带南北分别以襄樊—广济断裂和栾川—明港—固始断裂为界,夹持于华北克拉通与扬子克拉通之间,向西以南阳盆地为界与秦岭造山带相接,向东与苏鲁造山带之间被郯庐断裂所截切(图 1a),是一个经历了多期次造山作用的复合型造山带(张国伟等, 1996Wu and Zheng, 2013刘晓春等, 2015)。

区内断裂构造发育,包括NW向和NE向两组。NW向断裂包括朱夏断裂、龟梅断裂、桐商断裂、晓天—磨子潭断裂、七里坪断裂和高桥断裂,NE向断裂包括大悟断裂、陡山河断裂和商麻断裂,以大致50 km等间距平行产出并截切NW向断裂呈棋盘格子状。其中,以大悟断裂和商麻断裂为界,桐柏—大别造山带从西到东可划分为桐柏、西大别和东大别地区(图 1a)。以龟梅断裂为界,桐柏—大别造山带可进一步划分为北段和南段(图 1b)。北段主要出露中元古代宽坪群、新元古代—早古生代二郎坪群和古元古代秦岭群。宽坪群主要由绿片岩相-角闪岩相变质的基性火山岩、碳酸盐岩夹基性火山岩及具有浊积岩特征的砂泥质岩互层组成;二郎坪群为一套角闪岩相变质火山-沉积岩,以基性—酸性火山岩和碳酸盐岩组合与细碎屑岩混杂为特点;秦岭群原岩主要为一套富铝、富碳沉积岩系,包含若干花岗质片麻岩侵入体,经历了角闪岩相-麻粒岩相变质(王宗起等, 2009刘晓春等, 2015Zhou et al., 2016)。北段在秦岭和桐柏地区称为北秦岭构造带,而在大别地区则称为北淮阳构造带,记录了华北克拉通南缘古生代增生造山作用(刘晓春等, 2015)。南段以桐商断裂、晓天—磨子潭断裂、七里坪断裂和高桥断裂为界,从北往南出露信阳群、苏家河群、桐柏/大别杂岩、红安群和随县群5个构造地层单元(Mi et al., 2015),主要记录了中生代华南与华北板块之间的俯冲碰撞作用。信阳群为一套泥盆纪—早三叠世增生杂岩,可进一步解体为龟山杂岩和南湾复理石(刘志刚等, 1992)。龟山杂岩主要由角闪岩相变质基性岩(斜长角闪岩)、白云石英片岩和白云母构造片麻岩组成,夹有变泥砂质岩、石英岩和少量变质酸性火山岩,代表秦岭大陆弧与弧前复理石的混杂体。南湾复理石与龟山杂岩构造接触,主体是一套由绿片岩相变质的互层状石英砂岩、泥质粉砂岩、泥质岩和少量硬砂岩组成的泥盆纪弧前盆地复理石建造(刘晓春等, 2015)。苏家河群为一套早古生代增生杂岩,由强烈变形的花岗岩、变辉长岩、云母片岩、长英质片麻岩、斜长角闪岩、大理岩和榴辉岩包体组成(Liu et al., 2008)。桐柏/大别杂岩由变质深成岩系和表壳岩系组成,变质深成岩系以新元古代TTG片麻岩和少量混合岩为主,其中可见超高压榴辉岩地体;表壳岩系由麻粒岩、斜长角闪岩、黑云斜长片麻岩和大理岩组成(Zheng et al., 2006Liu and Liou, 2011)。根据原岩成分差异,以浠水—桐城断裂为界可分为北大别和南大别杂岩(Zhao et al., 2011)。新元古代红安群由长英质片岩、白云母钠长片岩、二云母片麻岩和少量榴辉岩、斜长角闪岩、大理岩、含磷变质岩系及石墨片岩组成(Liu et al., 2008)。随县群又称为木兰山蓝片岩单元,主要为一套新元古代火山-沉积岩(Liu et al., 2008)。区内岩浆岩发育,尤以燕山期岩浆活动最为强烈,主要为大量陆相火山岩、中酸性花岗岩和少量镁铁质—超镁铁质岩。燕山期火山岩以英安岩-流纹岩组合为特征,主要沿桐柏—大别造山带北麓信阳—商城—霍山一带分布,在晓天—磨子潭断裂以南未见出露。同时期的花岗岩分布广且规模大,沿桐商断裂自西向东依次分布七尖峰、鸡公山、灵山、新县和商城等岩基。此外,还分布众多早白垩世中酸性小型斑岩体,产出受网格状构造系统控制,具等间距成群成带展布的特征,与斑岩型钼矿关系密切,代表岩体包括天目山岩体、黄家沟岩体、肖畈岩体、母山岩体、大银尖岩体、千鹅冲岩体、宝安寨岩体、汤家坪岩体和沙坪沟岩体(Chen et al., 2017b)。少量镁铁质—超镁铁质岩呈小规模侵入体或岩墙形式产出(Zhao et al., 2011)。

七尖峰岩体出露于桐柏地区新城—黄陂断裂以南,沿北西-南东向呈纺锤状产出,出露面积约为300 km2,主要侵位于随县群中,局部被上白垩统寺沟组角度不整合覆盖。岩体具有明显分带性,由外至内可分为外带中粒斑状黑云二长花岗岩、中带中粒(含斑)黑云二长花岗岩、内带中粒黑云二长花岗岩(图 2)。岩石具块状构造(图 3ab),细粒—中粗粒花岗结构(图 3c),局部可见似斑状结构。岩体内部无变形,仅在边部发育宽约2 m片麻理带,具弱片麻状构造。主要组成矿物为斜长石(30%~35%)、钾长石(35%~40%)、石英(20%~25%)、少量黑云母和角闪石(< 5%,图 3d),副矿物出现磁铁矿、锆石、榍石和磷灰石。斜长石呈半自形板状,大小一般1~2 mm,杂乱分布,局部被绢云母及少量方解石交代。钾长石呈半自形-他形粒状,大小一般2~5 mm,部分1~2 mm,少数可达5~7 mm,可见蠕英交代结构,轻微土化。石英呈他形粒状,大小一般1~2 mm,部分可达2~5 mm,星散状、填隙状分布。黑云母呈片状,一般0.5~1 mm,零星分布,局部被绿泥石交代。

图 2 七尖峰岩体地质图(据陈超等, 2018修改) 1—中粒黑云母二长花岗岩;2—含斑细粒黑云母二长花岗岩;3—含斑中粗粒黑云母二长花岗岩;4—中粗粒黑云母二长花岗岩;5—斑状中粒黑云母二长花岗岩;6—随县群;7—耀岭河组;8—陡山沱组;9—寺沟组;10—第四系;11—片麻状花岗岩;12—超镁铁质岩;13—变辉长辉绿岩;14—桐柏杂岩;15—不整合;16—断裂;17—前人采样点;18—本文采样点 Fig. 2 Geological map of the Qijianfeng pluton (modified from Chen et al., 2018) 1-Medium-grained biotite monzonite; 2-Phenocryst-bearing fine-grained biotite monzonite; 3-Phenocryst-bearing medium-to coarse-grained biotite monzonite; 4-Medium-to coarse-grained biotite monzonite; 5-Porphyritic medium-grained biotite monzonite; 6-Suixian Group; 7-Yaolinghe Formation; 8-Doushantuo Formation; 9-Sigou Formation; 10-Quaternary; 11-Gneissic granite; 12-Ultramafic rock; 13-Meta-gabbro/diabase; 14-Tongbai complex; 15-Unconformity; 16-Fault; 17-Sampling location of previous studies; 18-Sampling location of this study
图 3 七尖峰花岗岩野外及镜下照片 a—七尖峰采石场;b—七尖峰花岗岩野外露头;c—中粗粒花岗结构;d—由钾长石+斜长石+石英+少量黑云母+角闪石组成花岗结构;Kfs—钾长石;Pl—斜长石;Qtz—石英;Bt—黑云母 Fig. 3 The photos of the Qijianfeng granite in the field and under the microscope a-Qijianfeng quarry; b-Outcrop of the Qijianfeng granite; c-Medium-to coarse-grained granitic texture; d-Granitic texture shown by K-feldspar, plagioclase, quartz, minor biotite and hornblende; Kfs-K-feldspar; Pl-Plagioclase; Qtz-Quartz; Bt-Biotite
3 分析测试方法

锆石分选在廊坊市宇能岩石矿物分选技术服务公司完成,岩石样品经破碎、淘洗后,采用重选和磁选技术进行初步分选,最后于双目镜下手工挑纯。锆石制靶及透、反射光显微照相和阴极发光照相在北京锆年领航科技有限公司完成。

锆石U-Pb定年及微量元素含量分析在湖北省地质实验测试中心利用LA-ICP-MS完成。激光器型号为美国Coherent Inc公司生产的GeoLasPro全自动版193 nm ArF准分子激光剥蚀系统,ICP-MS型号为美国Agilent公司生产的7700X型电感耦合等离子质谱仪。本次分析的激光束斑直径为32 μm。样品测试时,每个点的分析时间为60 s,其中背景信号10 s,样品剥蚀40 s,管路吹扫10 s。锆石微量元素含量利用NIST 610作为外标,Si作为内标进行定量计算。锆石U-Pb定年分析采用锆石标准物质91500作为外标进行同位素分馏校正,每分析5个样品点分析2次91500,同时采用Plésovice作为监控标样。锆石样品的同位素比值和元素含量采用ICPMSDataCal (Liu et al., 2010b)进行处理分析,U-Pb年龄谐和图绘制和年龄加权平均计算采用Isoplot 3.0 (Ludwig, 2003)完成。

锆石Lu-Hf同位素分析在中南矿产资源监督检测中心LA-MC-ICPMS实验室进行,所用仪器为RESOlution LR 193 nm激光剥蚀系统和Neptune型多接收电感耦合等离子体质谱仪。分析点选在锆石U-Pb分析点上或附近。激光剥蚀脉冲速率8~10 Hz,激光束斑直径43 μm,激光束能量密度15 J/cm2。采用锆石标准物质91500和Plésovice监控仪器的稳定性,所获实验数据通过ICPMSDataCal (Liu et al., 2010b)进行处理分析。采用176Lu衰变常数1.867×10-11a-1和样品176Lu/177Hf实测值进行εHf(t)和两阶段Hf模式年龄计算。两阶段Hf模式年龄计算假定大陆地壳的176Lu/177Hf平均值为0.015,球粒陨石和亏损地幔现今176Hf/177Hf和176Lu/177Hf比值分别为0.282785和0.0336、0.28325和0.0384。

全岩主、微量元素及Sr-Nd同位素分析均在武汉上谱分析科技有限责任公司完成。主量元素含量利用日本理学PrimusⅡX射线荧光光谱仪(XRF)分析完成,采用标准物BHVO-2、GBW07103、GBW07105、GBW07111、GBW07112进行监控,分析精度优于5%。微量元素含量利用Agilent 7700e ICP-MS分析完成,测试过程中,以国际标样AGV-2、BHVO-2、BCR-2、RGM-2进行质量监控,元素含量大于10×10-6的分析精度优于5%,小于10×10-6的分析精度优于10%。Sr-Nd同位素利用美国Thermo Fisher Scientific公司的Neptune Plus型多接收电感耦合等离子体质谱仪(MC-ICP-MS)完成。Sr、Nd同位素分析过程分别采用NBS SRM 987和JNdi-1作为仪器监控标样,获得NBS SRM 987的87Sr/86Sr分析测试值为0.710239±10(2SD,n=8),JNdi-1的143Nd/144Nd分析测试值为0.512114±6(2SD,n=8),与各自的推荐值在误差范围内一致,保证了仪器的稳定性。采用BCR-2和RGM-2作为流程监控标样,获得BCR-2的87Sr/86Sr分析测试值为0.705038±8(2SD, n=4)、143Nd/144Nd分析测试值为0.512630±8(2SD, n=4),获得RGM-2的87Sr/86Sr分析测试值为0.704184±10(2SD, n=4)、143Nd/144Nd分析测试值为0.512802±6(2SD, n=4),分别与相应的推荐值在误差范围内一致,保证了实验流程的可靠性。Sr-Nd同位素计算采用公式如下:

其中,t为样品的年龄,下脚标S、CHUR、DM分别代表样品、球粒陨石和亏损地幔,fccfsfDM分别为地壳、样品和亏损地幔的fSm/Ndfcc=-0.4,fDM=0.0859,(143Nd/144Nd)DM =0.51315,(147Sm/144Nd)DM =0.2137,Rb衰变常数为1.42×10-11 a-1,Sm衰变常数为6.54×10-12 a-1

4 测试结果

对样品17QJF01进行了LA-ICP-MS锆石U-Pb定年,结果见表 1。对5件代表性岩石样品进行了主、微量元素和Sr-Nd同位素测试,结果分别见表 2表 3。样品17QJF01的锆石原位Hf同位素分析结果见表 4

表 1 七尖峰花岗岩(17QJF01)LA-ICP-MS锆石U-Pb测试结果 Table 1 LA-ICP-MS zircon U-Pb analytical data for the Qijianfeng granite (17QJF01)
表 2 七尖峰花岗岩主(%)、微量(10-6)元素分析结果 Table 2 Major(%)and trace elements(10-6)compositions of the Qijianfeng granite
表 3 七尖峰花岗岩Sr-Nd同位素分析结果 Table 3 Sr-Nd isotopic composition of the Qijianfeng granite
表 4 七尖峰花岗岩锆石Lu-Hf同位素分析结果 Table 4 In situ Lu-Hf isotopic data of zircon from the Qijianfeng granite
4.1 锆石U-Pb年龄

样品17QJF01中锆石多呈自形长柱状,长宽比为1:2~1:4,阴极发光图像显示锆石具有清晰的岩浆振荡环带(图 4a)。对其中19个颗粒进行了19个点的U-Pb同位素分析,所分析的锆石Th含量介于135×10-6~849×10-6,U含量介于503×10-6~2102×10-6,Th/U比值为0.2~0.8。19个分析点均落于谐和线上(图 4b),206Pb/238U年龄比较集中,变化于137~144 Ma(图 4c),加权平均年龄为(140±1) Ma (MSWD=0.58)。

图 4 七尖峰花岗岩锆石阴极发光图像(a,实线和虚线圈分别代表U-Pb年龄和Hf同位素测点,“/”两侧分别为U-Pb年龄和εHf(t)值)、LA-ICP-MS锆石U-Pb年龄谐和图(b)和加权平均年龄图(c) Fig. 4 Representative cathodoluminescence (CL) images of zircon grains (a, the solid and dotted circles represent the analysis spots for U-Pb dating and Hf isotope, respectively. The U-Pb age and εHf(t) are shown on both sides of the slash), LA-ICP-MS zircon U-Pb concordia diagram (b) and weighted average age diagram (c) of the Qijianfeng granite
4.2 岩石地球化学特征

5件花岗岩样品SiO2含量介于72.88%~73.60%(扣除挥发分,下同),Al2O3含量介于14.48%~14.86%,K2O含量介于3.84%~4.15%,Na2O含量介于4.65%~4.81%,K2O/Na2O比值介于0.80~0.88。Fe2O3T含量介于1.24%~1.40%,MgO含量介于0.33%~0.36%,Mg#介于33~35。在TAS和An-Ab-Or图解上均落于花岗岩范围内(图 5ab)。样品铝饱和指数ACNK值为1.00~1.02,属弱过铝质(图 5c)。在SiO2-K2O图上,样品均落于高钾钙碱性系列范围内(图 5d)。微量元素方面,所有样品均表现出贫Cr (2.34×10-6~2.69×10-6)和Ni (2.19×10-6~3.01×10-6)等过渡金属元素、贫Y (5.65×10-6~5.95×10-6)和Yb (0.52×10-6~0.59×10-6)等重稀土元素及富Sr (620×10-6~642×10-6)的特征。

图 5 七尖峰花岗岩主量元素成分图解 a—TAS图解(据Middlemost, 1994);b—An-Ab-Or图解(据O’connor and Colo, 1965);c—A/NK-A/CNK图解(据Maniar and Piccoli, 1989);d—K2O-SiO2图解(据Peccerillo and Taylor, 1976),早期(>130 Ma)和晚期(< 130 Ma)花岗岩参考文献见表 5 Fig. 5 The diagrams of major elements for the Qijianfeng granite a-TAS diagram (after Middlemost, 1994); b-An-Ab-Or diagram (after O'connor and Colo, 1965); c-A/NK-A/CNK diagram (after Maniar and Piccoli, 1989); d-K2O-SiO2 diagram (after Peccerillo and Taylor, 1976). The references for early (>130 Ma) and late-stage (< 130 Ma) granites are shown in Table 5

岩石的稀土元素总量介于85.4×10-6~95.0×10-6,在球粒陨石标准化的稀土配分模式图上(图 6a),表现出轻稀土富集,重稀土平坦的分布特征((La/Yb)N=27.4~30.1, (Gd/Yb)N=2.21~2.60),无显著的铕异常(Eu/Eu*=0.83~0.94)。在原始地幔标准化的多元素蛛网图上(图 6b),七尖峰花岗岩样品显示出富集大离子亲石元素(Rb、Th、K),亏损高场强元素(Nb、Ta、P、Ti)的特征。

图 6 七尖峰花岗岩球粒陨石标准化的稀土配分模式图(a)及原始地幔标准化的多元素蛛网图(b),球粒陨石和原始地幔标准化值引自Sun and McDonough(1989) Fig. 6 Chondrite-normalized REE patterns (a) and primitive mantle-normalized spider diagrams (b) for the Qijianfeng granite. Normalization values for chondrite and primitive mantle after Sun and McDonough(1989)
4.3 Sr-Nd同位素地球化学特征

5件样品具有比较均一的87Sr/86Sr比值(0.708748~0.709081)、143Nd/144Nd比值(0.511750~0.511776),按t=140 Ma计算获得Sr同位素初始值ISr=0.7075~0.7078, εNd(t)值为-15.5~-15.1(图 7),对应的两阶段Nd模式年龄TDM2(Nd)=2.15~2.19 Ga。

图 7 七尖峰花岗岩ISr-εNd(t)图解 底图及华夏陆块、华北陆块(太行、鲁中、鲁西—胶北)、大别片麻岩、大别早白垩世花岗岩等范围来自赵子福等(2009)及其中参考文献,图例同图 5 Fig. 7 Whole-rock ISr-εNd(t) diagram for the Qijianfeng granite The fields of Cathaysia Block, North China Craton (Taihang, Luzhong, Luxi and Jiaobei), Dabie gneiss and Dabie early Cretaceous granite modified from Zhao et al. (2009) and references therein. Symbols as for Fig. 5
4.4 锆石Hf同位素

对15个锆石颗粒进行了原位Hf同位素分析,获得176Hf/177Hf比值介于0.282135~0.282328,按t=140 Ma进行回算,获得εNd(t)值介于-19.9~-13.2,对应的两阶段Hf模式年龄TDM2(Hf)介于2.00~2.43 Ga(图 8)。

图 8 七尖峰花岗岩锆石t-εNd(t)演化图 灰色区域代表华北陆块(太华群、熊耳群),北大别杂岩数据来自Zhao et al., 2008, 南大别杂岩数据来自Xia et al., 2009Zheng et al., 2006, 早期(>130 Ma)和晚期(< 130 Ma)花岗岩参考文献见表 5 Fig. 8 Zircon t versus εNd(t) diagram for the Qijianfeng granite Gray field represents the North China craton (Taihua Group and Xiong'er Group), data source: the north Dabie complex after Zhao et al., 2008, the south Dabie complex after Xia et al., 2009 and Zheng et al., 2006. The references for early (>130 Ma) and late-stage (< 130 Ma) granites see Table 5
5 讨论 5.1 侵位时代

前人采用全岩Rb-Sr、黑云母K-Ar、单颗粒锆石U-Pb等不同定年方法对七尖峰岩体的形成时代进行过研究,获得的年龄结果从115~262 Ma不等(陈超等, 2018)。由于Rb-Sr同位素体系封闭温度低,易受到后期热事件扰动;K-Ar年龄记录的是冷却年龄,可能显著小于岩体的真实侵位年龄;单颗粒锆石U-Pb法对于具有复杂核边结构的锆石,获得的结果为混合年龄等原因,导致早先的年龄数据不能很好地代表七尖峰岩体的真实侵位年龄。

Zhang et al. (2013)获得七尖峰斑状角闪黑云二长花岗岩LA-ICP-MS锆石U-Pb年龄为(133.1±0.5) Ma。陈超等(2018)报道七尖峰中粒斑状黑云二长花岗岩LA-ICP-MS锆石U-Pb年龄为(141±0.98) Ma。本研究显示,七尖峰岩体的锆石多呈自形长柱状,且具有清晰的岩浆振荡环带,所分析点的Th/U比值为0.2~0.8,表现出典型的岩浆锆石特征(吴元保等, 2004)。高精度锆石U-Pb年代学研究结果获得(140±1) Ma的年龄,与最近报道的LA-ICP-MS锆石U-Pb年龄在误差范围内一致(Zhang et al., 2013; 陈超等, 2018),代表了七尖峰花岗岩的结晶年龄,说明七尖峰花岗岩于早白垩世发生侵位。

5.2 岩石成因

七尖峰岩体具有高SiO2(72.88%~73.60%)、低MgO(0.33%~0.36%),高Sr(620×10-6~642×10-6)、Sr/Y(107~111)比值,低Y(5.65×10-6~5.95×10-6)、Yb(0.52×10-6~0.59×10-6)的地球化学特征,与典型埃达克岩非常相似(SiO2≥56%, MgO < 3%, Sr≥400×10-6, Y≤18×10-6, Yb≤1.9×10-6, Sr/Y≥40, Defant and Drummond, 1990)。在Sr/Y-Y和(La/Yb)N-YbN图解中(图 9ab),七尖峰花岗岩样品均落于埃达克岩范围内。

图 9 七尖峰花岗岩Sr/Y-Y图解(a, Defant and Kepezhinskas, 2002)和(La/Yb)N-YbN图解(b, Drummond and Defant, 1990),图例同图 5 Fig. 9 Sr/Y versus Y diagram (a, after Defant and Kepezhinskas, 2002) and (La/Yb)N versus YbN diagram (b, after Drummond and Defant, 1990) for the Qijianfeng granite. Symbols as for Fig. 5

目前对埃达克岩的成因机制存在不同认识,主要包括:(1)俯冲板片部分熔融(Defant and Drummond, 1990);(2)玄武质岩浆结晶分异(Castillo et al., 1999);(3)幔源镁铁质岩浆与壳源长英质岩浆混合(Guo et al., 2007; 陈斌等, 2013);(4)加厚/拆沉下地壳部分熔融(Atherton and Petford, 1993; Xu et al., 2002; Gao et al., 2004)。七尖峰花岗岩具有相当低的MgO(0.33%~0.36%)、Cr(2.34×10-6~2.69×10-6)和Ni(2.19×10-6~3.01×10-6),且缺乏共生的中-基性岩端元,故不可能由玄武质岩浆结晶分异形成。此外,野外露头尺度未见暗色微粒包体,薄片尺度未发现针状磷灰石等指示岩浆混合的岩石学证据,且岩石的Sr-Nd同位素及锆石Hf同位素相当均一,源区主要为古老地壳物质,而无幔源物质的加入,故幔源镁铁质岩浆与壳源长英质岩浆混合模式也不适合用来解释七尖峰花岗岩的埃达克岩地球化学特征。俯冲板片熔融形成的埃达克岩(O型)通常相对富Na2O(K2O/Na2O < 0.5,张旗等, 2004),而七尖峰花岗岩相对富K2O,K2O/Na2O比值为0.80~0.88,表现出与下地壳部分熔融成因的埃达克岩相似的特征(图 10a)。同时,七尖峰花岗岩样品具有相对较高的Rb/Sr比值(0.20~0.22),明显高于板片熔融形成的埃达克岩(Rb/Sr < 0.05, Huang et al., 2009)。另外,俯冲板片熔融形成的埃达克岩通常具有MORB-like同位素特征(Defant and Drummond, 1990),而七尖峰花岗岩富集的Sr-Nd同位素组成ISr=0.7075~0.7078,εNd(t)=-15.5~-15.1,TDM2=2.15~2.19 Ga表明其为古老地壳部分熔融的产物,进一步排除了俯冲板片部分熔融的可能性。此外,板片熔融成因和拆沉下地壳部分熔融成因的埃达克岩,通常因与上覆地幔橄榄岩相互作用而具有相对较高的MgO、Cr和Ni含量,而七尖峰花岗岩样品具有极低的MgO (0.33%~0.36%)、Cr(2.34×10-6~2.69×10-6)和Ni(2.19×10-6~3.01×10-6)含量,与1.0~4.0 Gpa条件下变玄武岩或榴辉岩实验熔体相当(Rapp et al., 1999),落在加厚下地壳部分熔融形成的埃达克岩区域内(图 10b)。总之,本研究表明,七尖峰花岗岩具有低MgO、Mg#、Cr和Ni,以及高SiO2富K2O的特征,属低镁埃达克岩,可解释为加厚下地壳部分熔融的产物。

图 10 七尖峰花岗岩Al2O3-K2O/Na2O图解(a, Deng et al., 2016)及SiO2-MgO图解(b, Wang et al., 2007),图例同图 5 Fig. 10 K2O/Na2O versus Al2O3 diagram (a, after Deng et al., 2016) and MgO versus SiO2 diagram (b, after Wang et al., 2007) for the Qijianfeng granite. Symbols as for Fig. 5

七尖峰花岗岩具有高SiO2、低CaO、MgO、Fe2O3T、Cr、Ni含量,富集轻稀土元素和大离子亲石元素、亏损高场强元素以及富集的Sr-Nd-Hf同位素组成,暗示其来源于古老地壳物质部分熔融。岩石ISr=0.7075~0.7078,εNd(t)=-15.5~-15.1,在Isr-εNd(t)图解中,七尖峰岩体的Sr-Nd同位素组成明显不同于华南板块、华北陆块(太行、鲁中、鲁西—胶北)的同位素组成,而与大别造山带广泛分布的早白垩世花岗岩Sr-Nd同位素组成相似,落于大别片麻岩区域内(图 7),指示大别片麻岩可能是七尖峰花岗岩的源岩,这也得到锆石Hf同位素证据的支持(图 8)。大量的研究也表明,大别造山带大面积出露的早白垩世花岗岩源自于扬子陆块北缘地壳物质的部分熔融(He et al., 2013; Xu et al., 2013)。由于大别片麻岩时代主要为新元古代,而七尖峰花岗岩中未发现新元古代继承锆石,且两阶段Nd模式年龄(2.15~2.19 Ga)和Hf模式年龄(2.00~2.43 Ga)明显比大别片麻岩时代老,说明其源区并不单一,可能为新元古代片麻岩和少量古元古代古老残片(如崆岭杂岩)混合熔融的产物。

大量研究表明埃达克岩是由榴辉岩或含石榴石角闪岩部分熔融形成(Defant and Drummond, 1990; Martin et al., 2005)。七尖峰花岗岩样品轻重稀土分馏强烈,且低Y和Yb,暗示源区残留相中出现石榴石;显著亏损高场强元素(Nb、Ta、P、Ti),表明源区有富Ti相或角闪石残留相;所有样品均富Sr且无负Eu异常,说明源区残留相中不出现斜长石。此外,七尖峰花岗岩样品具有较低的Nb/Ta比值(15~16)和较高的Zr/Sm比值(42~52),指示其源区残留相为以角闪石为主(Foley et al., 2002)。实验岩石学研究表明,斜长石在P>1.2 Gpa时(相当于40 km深度)变得不稳定,发生分解并释放Sr (Moyen, 2009);变质基性岩部分熔融过程中,角闪石在P≤2.2~2.5 Gpa条件下保持稳定(Xiong et al., 2011)。上述微量元素特征共同指示了七尖峰花岗岩源区残留相组合,表明其形成于加厚地壳部分熔融。此外,锆石饱和温度计是估算花岗质岩浆形成温度的有效工具,七尖峰花岗岩样品Zr含量介于115×10-6~126×10-6,利用Watson and Harrison(1983)提出的锆石饱和温度计获得TZr为754~762℃。因此,七尖峰花岗岩可能由早白垩世加厚下地壳含石榴石角闪岩在754~762℃条件下部分熔融形成。

5.3 构造与成矿意义

高压变质岩的研究表明,桐柏造山带高压变质作用及退变质作用分别发生于255 Ma和238 Ma左右(Liu et al., 2010a)。七尖峰花岗岩侵位于早白垩世,明显属于碰撞后岩浆作用的产物。最近的矿产地质调查工作在环七尖峰地区发现了一系列钼矿化(谭超等, 2018),同时在桐柏南缘的湖北随县发现了黄家沟中型钼矿床(Chen et al., 2017a),但相比于大别地区与早白垩世碰撞后花岗岩密切相关的众多钼矿床,桐柏地区的钼矿在数量和规模上都明显不及大别地区。

本文对桐柏—大别地区天目沟、七尖峰、黄家沟、母山、陡坡、大银尖、千鹅冲、宝安寨、姚冲、汤家坪、沙坪沟等11个成矿岩体进行了综合对比分析,其成岩成矿时代及微量元素特征见表 5。根据成矿岩体的地球化学特征、成岩成矿时代及可分为早、晚两个阶段,早阶段(>130 Ma)包括母山、陡坡、七尖峰、黄家沟和姚冲岩体,主要为花岗岩和少量石英二长岩(图 5ab),成分以准铝质为主(图 5c),多为中-高钾钙碱性系列(图 5d),并表现出埃达克质特征,如高Sr、低Y、高Sr/Y和(La/Yb)N比值(表 5),在Sr/Y-Y图解和(La/Yb)N-YbN图解中落在埃达克岩范围内(图 9ab);晚阶段包括天目沟、大银尖、千鹅冲、宝安寨、汤家坪、沙坪沟岩体,主要为花岗岩,酸性程度较早阶段更高(图 5a),多为弱过铝质,高钾钙碱性-钾玄岩系列,在Sr/Y-Y图解和(La/Yb)N-YbN图解中大多落在岛弧岩浆岩区域内(图 9ab)。其中,早阶段岩体相较于晚阶段显示出更高的(La/Yb)N比值,表明早阶段成矿岩体经历了更强烈的轻重稀土分馏,可能源于深部含石榴石残留相部分熔融的产物。在MgO-SiO2图解上,早阶段具埃达克质岩特征的岩体均落在加厚下地壳部分熔融形成的埃达克岩区域内(图 10b)。此外,晚阶段岩体的Eu/Eu*普遍较低(0.06~0.75,表 5),负Eu异常显著,而早阶段岩体的Eu/Eu*则相对较高,大部分在1左右,几乎不具Eu异常,说明晚阶段岩体源区有斜长石残留或岩浆经历了斜长石的分离结晶。由于晚阶段岩体在La-La/Sm图解中表现出明显的部分熔融趋势,暗示其负Eu异常可能主要为源区有斜长石残留导致(陈伟等, 2018)。因此,本文认为晚阶段岩体形成深度较浅,可能是非加厚地壳部分熔融的产物。早、晚两阶段成矿岩体岩石成因上的差别可能是导致早阶段以小—中型钼矿为主,而晚阶段以中—大型为主乃至出现超大型钼矿的根本原因(陈伟等, 2018)。

表 5 桐柏—大别造山带早白垩世与钼成矿相关花岗岩特征汇总 Table 5 Summary of the early Cretaceous Mo-related granites in the Tongbai-Dabie orogenic belt

事实上,前人对东大别碰撞后花岗岩开展了大量的研究,研究结果表明这些碰撞后花岗岩主要形成于早白垩世,根据微量元素特征的差异可划分为早、晚两期:早期花岗岩(>130 Ma)具有典型的埃达克岩地球化学特征,表现为高Sr、低Y、高Sr/Y比值、亏损HREE以及无Eu负异常,被认为是由加厚下地壳(>50 km)部分熔融形成;晚期花岗岩(< 130 Ma)则不具埃达克质特征,而表现出低Sr、高Y、低Sr/Y比值、相对弱的轻重稀土分馏及显著的Eu、Sr负异常,被认为是由相对较薄的地壳(约35 km)部分熔融形成(马昌前等, 2003He et al., 2011; Xu et al., 2013)。因此,桐柏—大别与钼成矿相关的岩体成因与东大别早白垩世碰撞后花岗岩成因类似,均指示了桐柏—大别造山带在早白垩世(约130 Ma)从碰撞挤压构造体制向碰撞后伸展构造体制转换,伴随加厚下地壳的垮塌、拆沉和岩石圈减薄及大规模岩浆作用和成矿(Chen et al., 2017b; 陈伟等, 2018)。

6 结论

(1)LA-ICP-MS锆石U-Pb定年结果表明,七尖峰花岗岩形成年龄为(140±1) Ma,属早白垩世。

(2)七尖峰花岗岩具有富SiO2、K2O,贫MgO、Cr和Ni,高Sr、Sr/Y比值,低Y、Yb、不具Eu异常的地球化学特征,属典型的C型埃达克岩,具有富集的Sr-Nd-Hf同位素组成,是古老的加厚下地壳物质部分熔融的产物。

(3)桐柏—大别造山带南缘早白垩世(约130 Ma)经历了从碰撞挤压地壳加厚到碰撞后伸展地壳减薄的构造垮塌演化过程,并伴生了两阶段钼成矿事件。

致谢: 锆石Hf同位素得到中南矿产资源监督检测中心童喜润、杨文武工程师的热情帮助,文稿修改过程中审稿专家和责任编辑给予了宝贵的修改意见,在此一并表示衷心的感谢!

参考文献
Atherton M P, Petford N. 1993. Generation of sodium-rich magmas from newly underplated basaltic crust[J]. Nature, 362(6416): 144-146. DOI:10.1038/362144a0
Castillo P R, Janney P E, Solidum R U. 1999. Petrology and geochemistry of Camiguin Island, southern Philippines:Insights to the source of adakites and other lavas in a complex arc setting[J]. Contributions to Mineralogy & Petrology, 134(1): 33-51.
Chen Bin, Chen Changjian, He Jingbo, Liu Ankun. 2013. Origin of Mesozoic high-Mg adakitic rocks from northeastern China:Petrological and Nd-Sr-Os isotopic constraints[J]. Chinese Science Bulletin, 58(20): 1941-1953 (in Chinese with English abstract). DOI:10.1360/972012-1254
Chen Chao, Mao Xinwu, Peng Shaonan, Liao Mingfang, Yang Jinxiang, Zhu Jin. 2018. LA-ICP-MS zircon U-Pb dating of Qijianfeng pluton in the Northern Hubei Province and its petrogenesis, metallogenic significance[J]. Resources Environment & Engineering, 32(2): 167-172 (in Chinese with English abstract).
Chen Q Z, Jiang S Y, Duan R C. 2017a. The geochemistry, U-Pb and Re-Os geochronology, and Hf isotopic constraints on the genesis of the Huangjiagou Mo deposit and related granite in the Dabie region, Hubei Province, China[J]. Ore Geology Reviews, 81: 504-517. DOI:10.1016/j.oregeorev.2016.07.009
Chen Wei, Mao Jingwen, Xu Zhaowen, Qu Xiaoming, Yu Yang. 2018. Two stages of the Cretaceous franitic magmatisms and Mo mineralizations in western Dabie orogenic belt[J]. Earth Science, 43(12): 4368-4650 (in Chinese with English abstract).
Chen W, Xu Z W, Lu X C, Yang X N, Li H C, Qu W J, Chen J Q, Wang H, Wang S H. 2013. Petrogenesis of the Bao'anzhai granite and associated Mo mineralization, western Dabie orogen, east-central China:Constraints from zircon U-Pb and molybdenite Re-Os dating, whole-rock geochemistry, and Sr-Nd-Pb-Hf isotopes[J]. International Geology Review, 55(10): 1220-1238. DOI:10.1080/00206814.2013.772322
Chen W, Xu Z W, Qiu W H, Li C, Yu Y, Wang H, Su Y. 2015. Petrogenesis of the Yaochong granite and Mo deposit, western Dabie orogen, eastern-central China:Constraints from zircon U-Pb and molybdenite Re-Os ages, whole-rock geochemistry and Sr-Nd-Pb-Hf isotopes[J]. Journal of Asian Earth Sciences, 103: 198-211. DOI:10.1016/j.jseaes.2015.01.010
Chen Y J, Wang P, Li N, Yang Y F, Pirajno F. 2017b. The collision-type porphyry Mo deposits in Dabie Shan, China[J]. Ore Geology Reviews, 81(2): 405-430.
Defant M J, Drummond M S. 1990. Derivation of some modern arc magmas by melting of young subducted lithosphere[J]. Nature, 347(6294): 662-665. DOI:10.1038/347662a0
Defant M, Kepezhinskas P. 2002. Adakites:some variations on a theme[J]. Acta Petrologica Sinica, 18(2): 129-142.
Deng J H, Yang X Y, Li S, Gu H L, Mastoi A S, Sun W D. 2016. Partial melting of subducted paleo-Pacific plate during the Early Cretaceous:Constraint from adakitic rocks in the Shaxi porphyry Cu-Au deposit, Lower Yangtze River Belt[J]. Lithos, 262: 651-667. DOI:10.1016/j.lithos.2016.07.039
Dong Y P, Santosh M. 2016. Tectonic architecture and multiple orogeny of the Qinling orogenic belt, Central China[J]. Gondwana Research, 29(1): 1-40. DOI:10.1016/j.gr.2015.06.009
Drummond M S, Defant M J. 1990. A model for trondhjemite-tonalite-dacite genesis and crustal growth via slab melting:Archean to modern comparisons[J]. Journal of Geophysical Research, 95(B13): 21503-21521.
Foley S, Tiepolo M, Vannucci R. 2002. Growth of early continental crust controlled by melting of amphibolite in subduction zones[J]. Nature, 417(6891): 837-840. DOI:10.1038/nature00799
Gao S, Rudnick R L, Yuan H L, Liu X M, Liu Y S, Xu W L, Ling W L, Ayers J, Wang X C, Wang Q H. 2004. Recycling lower continental crust in the North China craton[J]. Nature, 432(7019): 892-897. DOI:10.1038/nature03162
Gao Y, Mao J W, Ye H S, Li F L, Li Y F, Luo Z Z, Xiong B K, Meng F. 2014. Geochronology, geochemistry and Sr-Nd-Pb isotopic constraints on the origin of the Qian'echong porphyry Mo deposit, Dabie orogen, east China[J]. Journal of Asian Earth Sciences, 85: 163-177. DOI:10.1016/j.jseaes.2014.02.004
Gao Y, Mao J W, Ye H S, Li Y F, Luo Z Z, Yang Z Q. 2016. Petrogenesis of ore-bearing porphyry from the Tangjiaping porphyry Mo deposit, Dabie orogen:Zircon U-Pb geochronology, geochemistry and Sr-Nd-Hf isotopic constraints[J]. Ore Geology Reviews, 79: 288-300. DOI:10.1016/j.oregeorev.2016.05.015
Guo F, Nakamuru E, Fan W M, Kobayoshi K, Li C W. 2007. Generation of Palaeocene Adakitic Andesites by Magma Mixing; Yanji Area, NE China[J]. Journal of Petrology, 48(4): 661-692. DOI:10.1093/petrology/egl077
He Y S, Li S G, Hoefs J, Huang F, Liu S A, Hou Z H. 2011. Post-collisional granitoids from the Dabie orogen:New evidence for partial melting of a thickened continental crust[J]. Geochimica et Cosmochimica Acta, 75(13): 3815-3838. DOI:10.1016/j.gca.2011.04.011
He Y S, Li S G, Hoefs J, Kleinhanns I C. 2013. Sr-Nd-Pb isotopic compositions of Early Cretaceous granitoids from the Dabie orogen:Constraints on the recycled lower continental crust[J]. Lithos, (156/159): 204-217.
Huang Fan, Wang Denghong, Lu Sanming, Chen Yuchuan, Wang Bohua, Li Chao. 2011. Molybdenite Re-Os isotopic age of Shapinggou Mo deposit in Anhui Province and mesozoic Mo ore-forming stages in East Qinling-Dabie mountain region[J]. Mineral Deposits, 30(6): 1039-1057 (in Chinese with English abstract).
Huang X L, Xu Y G, Lan J B, Yang Q J, Luo Z Y. 2009. Neoproterozoic adakitic rocks from Mopanshan in the western Yangtze Craton:Partial melts of a thickened lower crust[J]. Lithos, 112(3): 367-381.
Li H C, Xu Z W, Lu X C, Chen W, Qu W J, Fu B, Yang X N, Yang J, Chen J Q. 2012. Constraints on timing and origin of the Dayinjian intrusion and associated molybdenum mineralization, western Dabie orogen, central China[J]. International Geology Review, 54(13): 1579-1596. DOI:10.1080/00206814.2012.684460
Li Mingli. 2009. Characteristics of Intermediate-Acid Small Intrusive Bodies and Metallogenic System of Molybdenum-Polymetallic Deposits in Mesozoic in Dabie Mountain, Henan Province[D]. Beijing: China University of Geosciences, 1-147 (in Chinese with English abstract).
Liu F L, Liou J G. 2011. Zircon as the best mineral for P-T-time history of UHP metamorphism:A review on mineral inclusions and U-Pb SHRIMP ages of zircons from the Dabie-Sulu UHP rocks[J]. Journal of Asian Earth Sciences, 40(1): 1-39.
Liu Xiaochun, Li Sanzhong, Jahn Borming. 2015. Tectonic evolution of the Tongbai-Hong'an orogen in central China:From oceanic subduction/accretion to continent-continent collision[J]. Science China Earth Sciences, 58(9): 1477-1496 (in Chinese). DOI:10.1007/s11430-015-5145-z
Liu X C, Jahn B M, Cui J J, Li S Z, Wu Y B, Li X H. 2010a. Triassic retrograded eclogites and Cretaceous gneissic granites in the Tongbai Complex, central China:Implications for the architecture of the HP/UHP Tongbai-Dabie-Sulu collision zone[J]. Lithos, 119(3): 211-237.
Liu X C, Jahn B M, Dong S W, Lou Y X, Cui J J. 2008. High-pressure metamorphic rocks from Tongbaishan, central China:U-Pb and 40Ar/39Ar age constraints on the provenance of protoliths and timing of metamorphism[J]. Lithos, 105(3): 301-318.
Liu Yongsheng, Hu Zhaochu, Zong Keqing, Gao Changgui, Gao Shan, Xu Juan, Chen Haihong. 2010b. Reappraisement and refinement of zircon U-Pb isotope and trace element analyses by LA-ICP-MS[J]. Chinese Science Bulletin, 55(15): 1535-1546 (in Chinese). DOI:10.1007/s11434-010-3052-4
Liu Zhigang, Niu Baogui, Ren Jishun. 1992. Disintegration of the Xinyang group and its tectonicimplications[J]. Geological Review, 38(4): 293-301 (in Chinese with English abstract).
Ludwig K R. 2003. User's manual for Isoplot 3.00: A Geochronological Toolkit for Microsoft Excel[M]. Berkeley Geochronology Center (Special Publications No. 4).
Ma Changqian, Yang Kunguang, Ming Houli, Lin Guangchun. 2004. The timing of tectonic transition from compression to extension in Dabieshan:evidence from Mesozoic granites[J]. Science in China (Series D:Earth Sciences), 33(9): 817-827 (in Chinese).
Maniar P D, Piccoli P M. 1989. Tectonic discrimination of granitoids[J]. Geological society of America bulletin, 101(5): 635-643. DOI:10.1130/0016-7606(1989)101<0635:TDOG>2.3.CO;2
Mao J W, Pirajno F, Xiang J F, Gao J J, Ye H S, Li Y F, Guo B J. 2011. Mesozoic molybdenum deposits in the east Qinling-Dabie orogenic belt:Characteristics and tectonic settings[J]. Ore Geology Reviews, 43(1): 264-293.
Martin H, Smithies R H, Rapp R, Moyen J F, Champion D. 2005. An overview of adakite, tonalite-trondhjemite-granodiorite (TTG), and sanukitoid:Relationships and some implications for crustal evolution[J]. Lithos, 79(1-2): 1-24.
Mi M, Chen Y J, Yang Y F, Wang P, Li F L, Wan S Q, Xu Y L. 2015. Geochronology and geochemistry of the giant Qian'echong Mo deposit, Dabie Shan, eastern China:Implications for ore genesis and tectonic setting[J]. Gondwana Research, 27(3): 1217-1235. DOI:10.1016/j.gr.2014.05.006
Middlemost E A K. 1994. Naming materials in the magma/igneous rock system[J]. Earth-Science Reviews, 37(3/4): 215-224.
Moyen J F. 2009. High Sr/Y and La/Yb ratios:The meaning of the "adakitic signature"[J]. Lithos, 112(3): 556-574.
O'connor J, Colo D. 1965. A classification for quartz-rich igneous rocks based on feldspar ratios[J]. United States Geological Survey Professional Paper, 525: 79-84.
Peccerillo A, Taylor S R. 1976. Geochemistry of Eocene calc-alkaline volcanic rocks from the Kastamonu area, northern Turkey[J]. Contributions to mineralogy and petrology, 58(1): 63-81. DOI:10.1007/BF00384745
Rapp R P, Shimizu N, Norman M D, Applegate G S. 1999. Reaction between slab-derived melts and peridotite in the mantle wedge:Experimental constraints at 3.8 GPa[J]. Chemical Geology, 160(4): 335-356. DOI:10.1016/S0009-2541(99)00106-0
Sun S S, Mcdonough W. 1989. Chemical and isotopic systematics of oceanic basalts:implications for mantle composition and processes[J]. Geological Society London Special Publications, 42(1): 313-345. DOI:10.1144/GSL.SP.1989.042.01.19
Tan Chao, Qu Jing, Leng Shuangliang, Tian Cheng. 2018. Geological characteristics and prospecting potential of molybdenum deposit in Qijianfeng Area of Suizhou-Zaoyang, Hubei Province[J]. Resources Environment & Engineering, 32(3): 362-366 (in Chinese with English abstract).
Wang G G, Ni P, Yu W, Chen H, Jiang L L, Wang B H, Zhang H D, Li P F. 2014a. Petrogenesis of Early Cretaceous post-collisional granitoids at Shapinggou, Dabie Orogen:Implications for crustal architecture and porphyry Mo mineralization[J]. Lithos, 184-187: 393-415. DOI:10.1016/j.lithos.2013.11.009
Wang P, Chen Y J, Fu B, Yang Y F, Mi M, Li Z L. 2014b. Fluid inclusion and H-O-C isotope geochemistry of the Yaochong porphyry Mo deposit in Dabie Shan, China:A case study of porphyry systems in continental collision orogens[J]. International Journal of Earth Sciences, 103(3): 777-797.
Wang P, Wang Y, Yang Y F. 2017. Zircon U-Pb geochronology and isotopic geochemistry of the Tangjiaping Mo deposit, Dabie Shan, eastern China:Implications for ore genesis and tectonic setting[J]. Ore Geology Reviews, 81: 466-483. DOI:10.1016/j.oregeorev.2016.05.004
Wang Q, Wyman D A, Zhao Z H, Xu J F, Bai Z H, Xiong X L, Dai T M, Li C F, Chu Z Y. 2007. Petrogenesis of Carboniferous adakites and Nb-enriched arc basalts in the Alataw area, northern Tianshan Range (western China):Implications for Phanerozoic crustal growth in the Central Asia orogenic belt[J]. Chemical Geology, 236(1/2): 42-64.
Wang Zongqi, Yan Quanren, Yan Zhen, Wang Tao, Jiang Chunfa, Gao Lianda, Li Qiugen, Chen Junlu, Zhang Yingli, Liu Ping, Xie Chunlin, Xiang Zhongjin. 2009. New division of the main tectonic units of the Qinling orogenic belt, Central China[J]. Acta Geologica Sinica, 83(11): 1527-1546 (in Chinese with English abstract).
Watson E B, Harrison T M. 1983. Zircon saturation revisited:temperature and composition effects in a variety of crustal magma types[J]. Earth and Planetary Science Letters, 64(2): 295-304.
Wu Yuanbao, Zheng Yongfei. 2004. Genesis of zircon and its constraints on interpretation of U-Pb age[J]. Chinese Science Bulletin, 49(15): 1554-1569 (in Chinese). DOI:10.1007/BF03184122
Wu Y B, Zheng Y F. 2013. Tectonic evolution of a composite collision orogen:An overview on the Qinling-Tongbai-Hong'an-Dabie-Sulu orogenic belt in central China[J]. Gondwana Research, 23(4): 1402-1428. DOI:10.1016/j.gr.2012.09.007
Xia Q X, Zheng Y F, Yuan H, Wu F Y. 2009. Contrasting Lu-Hf and U-Th-Pb isotope systematics between metamorphic growth and recrystallization of zircon from eclogite-facies metagranites in the Dabie orogen, China[J]. Lithos, 112(3): 477-496.
Xiong X L, Keppler H, Audetat A, Ni H W, Sun W D, Li Y. 2011. Partitioning of Nb and Ta between rutile and felsic melt and the fractionation of Nb/Ta during partial melting of hydrous metabasalt[J]. Geochimica et Cosmochimica Acta, 75(7): 1673-1692. DOI:10.1016/j.gca.2010.06.039
Xu H J, Ma C Q, Zhang J F, Ye K. 2013. Early Cretaceous low-Mg adakitic granites from the Dabie orogen, eastern China:Petrogenesis and implications for destruction of the over-thickened lower continental crust[J]. Gondwana Research, 23(1): 190-207. DOI:10.1016/j.gr.2011.12.009
Xu J F, Shinjo R, Defant M J, Wang Q, Rapp R P. 2002. Origin of Mesozoic adakitic intrusive rocks in the Ningzhen area of east China:Partial melting of delaminated lower continental crust?[J]. Geology, 30(12): 1111-1114. DOI:10.1130/0091-7613(2002)030<1111:OOMAIR>2.0.CO;2
Yang Meizhen, Zeng Jiannian, Ren Aiqun, Lu Jianpei, Pan Sidong. 2011. Characteristics of Mo mineralization and zircon LA-ICP-MS U-Pb geochronology of Mushan Mo deposit from Luoshan county, Henan province[J]. Mineral Deposits, 30(3): 435-447 (in Chinese with English abstract).
Yang Y F, Wang P, Chen Y J, Li Y. 2017. Geochronology and geochemistry of the Tianmugou Mo deposit, Dabie Shan, eastern China:Implications for ore genesis and tectonic setting[J]. Ore Geology Reviews, 81: 484-503. DOI:10.1016/j.oregeorev.2016.04.010
Yang Zeqiang. 2007. Re-Os isotopic ages of Tangjiaping molybdenum deposit in Shangcheng County, Henan and their geological significance[J]. Mineral Deposits, 26(3): 289-295 (in Chinese with English abstract).
Zhang Guowei, Meng Qingren, Yu Zaiping, Sun Yong, Zhou Dingwu, Guo Anlin. 1996. Orogenesis and dynamics of the Qinling orogen[J]. Science in China (Series D:Earth Sciences), 9(3): 225-234 (in Chinese).
Zhang Qi, Xu Jifeng, Wang Yan, Xiao Long, Liu Hongtao, Wang Yuanlong. 2004. Diversity of adakite[J]. Geological Bulletin of China, 23(Z2): 959-965 (in Chinese with English abstract).
Zhang J Y, Ma C Q, Li J W, She Z B, Zhang C. 2013. Geochronology and geochemistry of the Early Cretaceous Jigongshan and Qijianfeng batholiths in the Tongbai orogen, central China:implications for lower crustal delamination[J]. International Journal of Earth Sciences, 102(4): 1045-1067.
Zhao Z F, Zheng Y F, Wei C S, Wu F Y. 2011. Origin of postcollisional magmatic rocks in the Dabie orogen:Implications for crust-mantle interaction and crustal architecture[J]. Lithos, 126(1): 99-114.
Zhao Zifu, Zheng Yongfei. 2009. Remelting of subducted continental lithosphere:Petrogenesis of Mesozoic magmatic rocks in the Dabie-Sulu orogenic belt[J]. Science in China (Series D:Earth Sciences), 52(9): 1295-1318 (in Chinese). DOI:10.1007/s11430-009-0134-8
Zhao Z F, Zheng Y F, Wei C S, Chen F K, Liu X M, Wu F Y. 2008. Zircon U-Pb ages, Hf and O isotopes constrain the crustal architecture of the ultrahigh-pressure Dabie orogen in China[J]. Chemical Geology, 253(3): 222-242.
Zheng Y F. 2008. A perspective view on ultrahigh-pressure metamorphism and continental collision in the Dabie-Sulu orogenic belt[J]. Chinese Science Bulletin, 53(20): 3081-3104 (in Chinese).
Zheng Y F, Zhao Z F, Wu Y B, Zhang S B, Liu X M, Wu F Y. 2006. Zircon U-Pb age, Hf and O isotope constraints on protolith origin of ultrahigh-pressure eclogite and gneiss in the Dabie orogen[J]. Chemical Geology, 231(1): 135-158.
Zhou Z J, Mao S D, Chen Y J, Santosh M. 2016. U-Pb ages and Lu-Hf isotopes of detrital zircons from the southern Qinling Orogen:Implications for Precambrian to Phanerozoic tectonics in central China[J]. Gondwana Research, 35: 323-337. DOI:10.1016/j.gr.2015.06.003
陈斌, 陈长健, 贺敬博, 刘安坤. 2013. 华北东部中生代高镁埃达克质岩浆的起源:岩石学和Nd-Sr-Os同位素证据[J]. 科学通报, 58(20): 1941-1953.
陈超, 毛新武, 彭少南, 廖明芳, 杨金香, 朱金. 2018. 鄂北七尖峰岩体LA-ICP-MS锆石U-Pb测年及其岩石成因、成矿意义[J]. 资源环境与工程, 32(2): 167-172.
陈伟, 毛景文, 徐兆文, 曲晓明, 于旸. 2018. 西大别白垩纪两阶段花岗岩成岩及钼成矿作用的讨论[J]. 地球科学, 43(12): 4368-4650.
黄凡, 王登红, 陆三明, 陈毓川, 王波华. 2011. 安徽省金寨县沙坪沟钼矿辉钼矿Re-Os年龄——兼论东秦岭-大别山中生代钼成矿作用期次划分[J]. 矿床地质, 30(6): 1039-1057. DOI:10.3969/j.issn.0258-7106.2011.06.005
李明立. 2009.河南省大别山地区中生代中酸性小岩体特征及钼多金属成矿系统[D].北京: 中国地质大学. http://cdmd.cnki.com.cn/Article/CDMD-11415-2009075396.htm
刘晓春, 李三忠, 江博明. 2015. 桐柏-红安造山带的构造演化:从大洋俯冲/增生到陆陆碰撞[J]. 中国科学:地球科学, 45(8): 1088-1108.
刘志刚, 牛宝贵, 任纪舜. 1992. 信阳群的解体及其大地构造意义[J]. 地质论评, 38(4): 293-301. DOI:10.3321/j.issn:0371-5736.1992.04.001
马昌前, 杨坤光, 明厚利, 林广春. 2003. 大别山中生代地壳从挤压转向伸展的时间:花岗岩的证据[J]. 中国科学(D辑:地球科学), (9): 817-827.
谭超, 渠婧, 冷双梁, 田成. 2018. 湖北随州-枣阳七尖峰地区钼矿地质特征及找矿前景分析[J]. 资源环境与工程, 32(3): 362-366.
王宗起, 闫全人, 闫臻, 王涛, 姜春发, 高联达, 李秋根, 陈隽璐, 张英利, 刘平, 谢春林, 向忠金. 2009. 秦岭造山带主要大地构造单元的新划分[J]. 地质学报, 83(11): 1527-1546. DOI:10.3321/j.issn:0001-5717.2009.11.001
吴元保, 郑永飞. 2004. 锆石成因矿物学研究及其对U-Pb年龄解释的制约[J]. 科学通报, 49(16): 1589-1604. DOI:10.3321/j.issn:0023-074X.2004.16.002
杨梅珍, 曾键年, 任爱群, 陆建培, 潘思东. 2011. 河南罗山县母山钼矿床成矿作用特征及锆石LA-ICP-MS U-Pb同位素年代学[J]. 矿床地质, 30(3): 435-447. DOI:10.3969/j.issn.0258-7106.2011.03.005
杨泽强. 2007. 河南商城县汤家坪钼矿辉钼矿铼-锇同位素年龄及地质意义[J]. 矿床地质, 26(3): 289-295. DOI:10.3969/j.issn.0258-7106.2007.03.005
张国伟, 孟庆任, 于在平, 孙勇, 周鼎武, 郭安林. 1996. 秦岭造山带的造山过程及其动力学特征[J]. 中国科学(D辑:地球科学), 26(3): 193-200.
张旗, 许继峰, 王焰, 肖龙, 刘红涛, 王元龙. 2004. 埃达克岩的多样性[J]. 地质通报, 23(Z2): 959-965.
赵子福, 郑永飞. 2009. 俯冲大陆岩石圈重熔:大别-苏鲁造山带中生代岩浆岩成因[J]. 中国科学:地球科学, 39(7): 888-909.
郑永飞. 2008. 超高压变质与大陆碰撞研究进展:以大别-苏鲁造山带为例[J]. 科学通报, 53(18): 2129-2152. DOI:10.3321/j.issn:0023-074X.2008.18.001