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1.
在青藏高原东南缘和扬子克拉通西缘,哀牢山-红河断裂带南段,产出了一些新生代富碱斑岩,本文选择绿春-金平一带的三类斑岩进行了年代学、地球化学和岩石成因研究,试图为研究区的壳幔相互作用和哀牢山-红河断裂带的关联提供新证据。研究区出露的三类富碱斑岩及其锆石U-Pb年龄分别是花岗斑岩(34.36±0.39Ma)、石英二长斑岩(35.48±0.39Ma)和正长斑岩(35.36±0.43Ma)。三类岩石的锆石ε_(Hf)(t)值分别是-6.4～+2.6、-1.5～+3.6和-3.1～+1.0。三类岩石具有相似的微量元素、稀土元素和同位素特征,具有富集大离子亲石元素、轻重稀土分馏强烈、亏损Nb、Ta和Ti等高场强元素的特征,具有弱的Eu负异常,~(87)Sr/~(86)Sr值为0.7067～0.7078,ε_(Nd)(t)为-3.8～-3.7。花岗斑岩和石英二长斑岩都来源于加厚的铁镁质下地壳,但正长斑岩来源于交代富集的岩石圈地幔,源区的富集可能是新元古代和晚古生代大洋俯冲交代导致的,印度与欧亚大陆的持续汇聚导致哀牢山-红河断裂带下部地壳和岩石圈地幔的增厚,在35Ma左右三江地区应力转变引起了岩石圈地幔的拆沉,使得软流圈上涌引起下地壳和岩石圈地幔的部分熔融,然后岩浆沿着地壳裂隙上涌和侵位,形成不同类型的富碱斑岩。  相似文献   

2.
大理笔架山铜矿区位于金沙江-红河富碱斑岩成矿带中部,与斑岩有关的铜(金)矿找矿取得了新突破。本文在详实的成矿斑岩岩相学观察基础上,开展了系统的岩石地球化学和年代学研究。与成矿相关的石英二长斑岩具有富碱(K2O+Na2O均值为9.97%)、富钾(K2O/Na2O均值为2.34)和准铝质(A/CNK均值为0.89)特征,属准铝质钾玄岩系列;微量元素具LILE(Rb、Ba、U、Th和Sr)富集和HFSE(Ta、Nb和Ti)亏损特征,与大陆地壳特征相似;稀土元素具LREE富集和Eu(均值0.73)弱负异常特征,与壳幔混合型花岗岩相近。岩石地球化学特征表明,石英二长斑岩源区具典型壳-幔混合特征,其中以部分熔融的古老地壳物质为主。LA-ICP-MS锆石U-Pb年龄(35.6±0.19 Ma)与金沙江-红河富碱斑岩带岩浆活动高峰期(45~30 Ma)一致。研究结果进一步佐证了本区富碱斑岩是在印-欧板块后碰撞伸展背景下,由加厚下地壳和上地幔部分熔融形成的,与金沙江-红河断裂的走滑构造事件相关。  相似文献   

3.
滇西新生代富碱斑岩及其深源包体的岩石学和地球化学特征   总被引：22，自引：6，他引：22  
滇西地区沿金沙江—哀牢山断裂带产出了一套第三纪富碱斑岩 ,其中包含有多种类型的深源包体 ,它们对于了解滇西地区的地幔组成与演化及壳幔相互作用有重要意义。介绍了鹤庆六合、剑川新华、甸心和石鼓小桥头等地的富碱斑岩及其深源包体的岩石类型和岩相学特征 ;通过对寄主岩及其包体的主量元素、微量元素、稀土元素和Pb、Sr、Nd同位素的分析 ,运用多种地球化学判别图解并结合实验岩石学和相平衡的研究结果 ,认为研究区的富碱斑岩属于钾玄岩系列的岩石 ,主要形成于后碰撞弧环境 ;富碱斑岩起源于滇西加厚地壳的下部 (约 5 5km处 ) ,源区岩石应是榴辉岩相的岩石 ;富碱斑岩的源区具有EMⅡ型富集地幔的地球化学特征 ,其成因可能和下地壳岩石与具有俯冲残留洋壳特征的地幔的混合作用有关  相似文献   

4.
贺娟  王启宇  闫国川 《地球科学》2018,43(8):2586-2599
前人对金沙江-红河构造带上的煌斑岩研究工作主要集中在南段哀牢山地区.对构造带中段鲁甸地区新发现的煌斑岩脉进行了锆石U-Pb年代学和全岩地球化学研究.结果表明,煌斑岩形成时代为始新世末期,与滇西新生代富碱斑岩高峰期一致.鲁甸煌斑岩具有高钾、富碱、高Mg#,富集大离子亲石元素（LILE）和轻稀土元素（LREE）,亏损高场强元素（HFSE,尤其是Ta-Nb-Ti）的特征.其岩浆源区为受俯冲流体和熔体交代的岩石圈地幔,源区组分为含金云母的尖晶石相方辉橄榄岩.结合同期的镁铁质火山岩和富碱斑岩研究成果,滇西区域的岩石圈地幔富集过程可能为元古宙时期与罗迪尼亚超大陆聚合相关的俯冲作用.始新世时期,在印度和亚洲大陆碰撞过程中,金沙江-红河构造带的富集岩石圈地幔发生拆沉或对流减薄,软流圈物质上涌,引发富集的岩石圈地幔部分熔融,形成本期煌斑岩岩浆作用.   相似文献   

5.
桐村地区与德兴矿区岩石系列相似,为高钾钙碱性系列;在岩石结构上,桐村地区花岗闪长岩为似斑状结构,德兴矿区花岗闪长斑岩为斑状结构。两者均为钙碱—碱质镁质I型花岗岩。桐村岩石富Si和K,A/CNK和K/(K+Na)值均小于德兴岩石。微量元素、同位素及岩石学特征表明桐村地区的物质来源以壳源为主,而德兴地区为有大量幔源物质参与的壳幔混合型,其原因可能与两区不同的构造位置有关。中晚侏罗世时,太平洋板块西向俯冲,下插板片发生部分熔融形成的岩浆与岩石圈地幔楔发生作用从而形成斑岩岩浆是桐村和德兴地区可能的成因模式。桐村矿床含矿斑岩的氧逸度、演化程度和地壳混染程度均较德兴斑岩铜矿高。对于同时代、近距离的岩浆岩形成如此规模悬殊的矿床还有许多问题值得研究和思考。  相似文献   

6.
滇中老街子Pb-Ag多金属矿床位于红河-哀牢山新生代富碱斑岩带的中段,是与富碱火山-岩浆热液密切相关的典型矿床。首次在该矿床深部发现70m宽的高Cu-Mo异常黄铁矿化蚀变正长斑岩和黄铁矿-辉钼矿矿脉(2073中段3#穿脉),认为该矿床深部存在明显的富碱斑岩-岩浆热液型铜-钼矿化叠加成矿作用。本文选取深部坑道内的辉钼矿-黄铁矿脉、黄铁矿-方铅矿脉和高Cu-Mo异常黄铁矿化蚀变正长斑岩进行辉钼矿-黄铁矿Re-Os同位素成矿年代研究,获得了辉钼矿Re-Os等时线年龄33.71±0.29Ma和加权平均值年龄33.99±0.22Ma,说明滇中老街子斑岩型铜-钼成矿作用时代为渐新世,与Cu-Mo异常黄铁矿化蚀变正长斑岩成岩年龄一致。黄铁矿的初始Os比值(0.3049~1.5549)及其γOs值(140.5~1126)指示老街子Pb-Ag多金属矿床金属成矿物质主要来源于壳幔相互作用而形成的岩浆。老街子Pb-Ag多金属矿床成岩成矿年龄和区域上富碱斑岩-岩浆热液型多金属矿床成岩成矿年龄(30~40Ma)大致相当,表明印度板块与欧亚板块碰撞期后,构造应力场发生转变形成大规模区域左行走滑断裂系统,在稳定块体内部诱发壳幔过渡层发生部分熔融形成富碱岩浆和成矿流体,成矿流体沿着构造薄弱部位形成富碱斑岩-岩浆热液型多金属矿床。  相似文献   

7.
郯庐断裂带中-南段中生代岩浆活动的构造背景与深部过程   总被引：47，自引：13，他引：47  
郯庐断裂带内岩浆岩及糜棱岩的年龄及野外研究表明以中-酸性为主的岩浆活动主要发生在早白垩世走滑运动的晚期,岩石化学以富钾、富碱为特征;稀土元素以轻稀土富集、重稀土亏损为特征;微量元素表现出富集大离子亲石元素,尤其是强不相容元素;同位素组成显示岩浆来源于壳幔过渡带.带内岩浆活动明显受断裂带控制,走滑晚期的岩浆活动起源于地幔底侵、壳幔相互作用下的壳幔过渡带,在伊泽奈崎板块斜向俯冲、中国东部遭受区域性剪切-挤压的背景下出现.在此背景下中国东部发生了岩石圈减薄,同时出现了一系列北东-北北东向已深切至壳幔边界的左行平移断裂系,从而诱发了大规模的岩浆活动.  相似文献   

8.
九顶山复式岩体沿北西向金沙江–红河断裂与南北向程海断裂交汇处发育,处于南北地洼区与滇西地洼区接触带,是滇西地洼期斑岩成矿带中段的代表性富碱斑岩体之一。该岩体由呈岩株、岩脉、岩墙或岩床等产出的斑状花岗岩、正长斑岩、(二长)花岗斑岩、碱长花岗斑岩和煌斑岩等组成。本文着重对正长斑岩的形成年代、岩石地球化学和成因特征开展研究,结果表明:正长斑岩的LA-ICP-MS锆石U-Pb年龄为34.6±0.7 Ma,即岩浆侵位于始新世(E2),属滇西地洼激烈期及新生代富碱岩浆活动高峰期(45~30 Ma)的产物;岩石具高硅(Si O256%)、高钾(K2O=3.38%~8.92%,K2O/Na2O1)、富碱(ALK=8.15%~11.15%)和低Mg O(3%)的特征,属钾玄岩系列–高钾钙碱性系列过铝质(A/CNK=0.71~1.22)花岗岩;在微量元素组成上,岩石高Sr(400×10-6)、低Y(18×10-6)和Yb(1.9×10-6),与陆内造山环境形成的"C型"钾质埃达克岩地球化学特征类似;全岩的Sr-Nd-Hf同位素组成特征显示岩浆源区是壳幔物质混合的"EMII型"富集地幔源。正长斑岩的形成应与印度–欧亚板块碰撞俯冲背景下,金沙江–红河断裂大规模左行走滑引起的热扰动和局部引张作用有关,在这种区域热–动力学条件下,地幔部分熔融与地壳物质发生混合作用,形成活化型壳幔混合源高钾富碱岩浆。  相似文献   

9.
滇西剑川富碱岩浆岩位于青藏高原东南缘的三江南段,是金沙江-红河富碱岩浆岩带的重要组成部分。剑川富碱岩浆岩包括花岗岩和正长岩两类岩石,前者主要有花岗斑岩和石英二长斑岩,后者主要是正长斑岩和粗面岩。本文对剑川富碱岩浆岩进行了主微量元素、锆石U-Pb年代学和Sr-Nd-Hf同位素特征研究。锆石U-Pb测年结果显示,剑川花岗岩结晶年龄为35. 1～36. 1Ma,正长岩结晶年龄为35. 7～35. 8Ma,均形成于始新世。花岗斑岩和石英二长斑岩的SiO_2含量为67. 92%～69. 93%,K_2O/Na_2O比值介于0. 86～1. 22,具有高钾钙碱性特征;正长斑岩和粗面岩的SiO_2含量为53. 94%～63. 51%,K_2O/Na_2O比值介于1. 30～2. 68,属于钾玄质岩石系列。两类岩石都富集轻稀土元素(LREE)和大离子亲石元素(LILE),相对亏损高场强元素(HFSE)。其中,花岗斑岩和石英二长斑岩有着较高的Sr、Sr/Y、La/Yb值和低的Y、Yb含量,具有埃达克质岩浆属性。结合Sr-Nd-Hf同位素研究认为,滇西剑川地区花岗岩起源于增厚的镁铁质新生下地壳部分熔融,正长岩是由交代富集的岩石圈地幔熔融产生的基性岩浆演化而来的产物。滇西剑川新生代富碱岩浆活动是对印度与欧亚板块晚碰撞阶段,岩石圈地幔发生对流减薄和软流圈物质上涌过程的响应。  相似文献   

10.
贵州从江地区花岗质斑岩的地球化学特征   总被引：3，自引：1，他引：2  
王敏 《贵州地质》1999,16(4):278-281
从江地区花岗质斑岩分布于摩花岗岩体的周级,主要有二长花岗斑岩、普通花斑岩、碱长花岗斑岩、混合花岗斑岩４种类型。就岩石化学特征而言,二长花岗斑岩以壳源为主, 幔源成分的壳幔混源成因;普通花岗斑岩属壳源交代成因;而混合花岗斑岩与区内负变质岩的岩石化学成分相似。  相似文献   

11.
Berzina AN  Berzina AP 《岩石学报》2008,24(12):2657-1668
The Aksug deposit, located in Altay-Sayan region of Russia, is one of the largest porphyry Cu-Mo deposits in Southern Siberia. The ore-bearing porphyries of the Aksug porphyry Cu-Mo system were formed in post-collisional environment. Geochemically they belong to calk-alkaline and high K-calk-alkaline series. Rocks are characterized by enrichment of LILE and depletion of HSFE and HREE, showing the importance of subduction-related components in magma generation. Large plutonic intrusions that host porphyry systems have been formed during collision. The origin of porphyritic rocks is dominantly the mantle with lower crustal contribution. The mainly economically important Cu-Mo mineralization is closely related to a porphyry series in time and space, being emplaced towards the end of magmatic activity. Though the emplacement of plutonic and ore-bearing porphyry complexes took place in different geodynamic environments, both complexes are characterized by certain similarity in geochemical composition, alkalinity, trace element content, Sr isotopic composition. This fact evidently indicates a common deep-seated magmatic source (at the lower crust-upper mantle level). Low initial 87 Sr/86 Sr, sulfur isotopic characteristics and presence of PGE-Co-Ni mineralization in associated pyrite-chalcopyrite ores suggest that mantle source of chalcophile elements was of high importance in porphyry Cu-Mo mineralization of the Aksug deposit.  相似文献   

12.
北衙金多金属矿床产出于滇西北富碱斑岩-多金属成矿带内。矿床严格受富碱斑岩及其成生的深大断裂构造控制,并发育热液交代现象,且在围岩内以产出充填型矿脉(囊)、交代型条带矿(似层状)为主,构成斑岩-矽卡岩成矿系统,具超大型金矿床规模。本文利用Re-Os同位素定年方法首次对北衙铁金多金属矿床全矿段金属硫化物成矿年龄进行精确测定,获得5件辉钼矿样品的模式年龄为37.46~39.44 Ma,其加权平均年龄为(38.48±0.54)Ma,等时线年龄为(37.9±2.5)Ma,两者在误差范围内一致,与区域及区内富碱斑岩锆石U-Pb年龄基本保持一致;辉钼矿中Re含量主体26.84×10-6~43.15×10-6之间,指示其成矿物质来源于上地幔和下地壳,为壳幔混合源;两者均指示成矿作用与该时期具幔壳混合源性质的富碱岩浆浅成侵入关系密切。  相似文献   

13.
We have determined the ages of the ore-bearing Tinggong porphyries and the Eocene granites using the LA-ICPMS zircon U-Pb method. Zircons from one adamellite porphyry and two diorite porphyries yield ages of 15.54±0.28 Ma, 15.02±0.25 Ma and 14.74±0.22 Ma, respectively. The ages of two granites are 50.48±0.71 Ma and 50.16±0.48 Ma. Light Rare Earth Elements(LREE) are enriched in the ore-bearing adamellite porphyries, which are high-K calc-alkaline and metaluminous, while Heavy Rare Earth Elements(HREE) and Y are strongly depleted, indicating an adakitic affinity. The Large Ion Lithophile Elements(LILE) of the adamellite porphyries are highly enriched, whereas some High Field Strength Elements(HFSE) are depleted. The diorite porphyry in this study is chemically similar to the adamellite porphyries, except that the Mg# of the diorite porphyry is a little higher, demonstrating more mantle contamination. Four samples from different rocks are selected for in situ zircon Hf isotopic analyses. The samples show positive εHf(t) values and young Hf model ages, indicating their derivation from juvenile crust. However, the adamellite porphyry and diorite porphyry formed in the Miocene exhibit more heterogeneous Hf isotopic ratios, with lower εHf(t) values than the granites formed in the Eocene, suggesting the involvement of old Indian continent crust in their petrogenesis. The geochronology and geochemistry of the adamellite porphyries and the diorite porphyries indicate that they formed from the same source region in a post-collisional environment, but contaminated by crust and mantle materials in different ratios. The metallic minerals formed mainly during the older adamellite porphyry stage, but they were recycled and reactivated by the diorite porphyry intrusion.  相似文献   

14.
The Alkaline porphyries in the Beiya area are located east of the Jinshajiang suture, as part of a Cenozoic alkali-rich porphyry belt in western Yunnan. The main rock types include quartz-albite porphyry, quartz-K-feldspar porphyry and biotite–K-feldspar porphyry. These porphyries are characterised by high alkalinity [(K2O + Na2O)% > 10%], high silica (SiO2% > 65%), high Sr (> 400 ppm) and 87Sr/86Sr (> 0.706)] ratio and were intruded at 65.5 Ma, between 25.5 to 32.5 Ma, and about 3.8 Ma, respectively. There are five main types of mineral deposits in the Beiya area: (1) porphyry Cu–Au deposits, (2) magmatic Fe–Au deposits, (3) sedimentary polymetallic deposits, (4) polymetallic skarn deposits, and (5) palaeoplacers associated with karsts. The porphyry Cu–Au and polymetallic skarn deposits are associated with quartz–albite porphyry bodies. The Fe–Au and polymetallic sedimentary deposits are part of an ore-forming system that produced considerable Au in the Beiya area, and are characterised by low concentrations of La, Ti, and Co, and high concentrations of Y, Yb, and Sc.The Cenozoic porphyries in western Yunnan display increased alkalinity away from the Triassic Jinshajiang suture. Distribution of both the porphyries and sedimentary deposits in the Beiya area are interpreted to be related to partial melting in a disjointed region between upper mantle lithosphere of the Yangtze Plate and Gondwana continent, and lie within a shear zone between buried Palaeo-Tethyan oceanic lithosphere and upper mantle lithosphere, caused by the subduction and collision of India and Asia.  相似文献   

15.
银厂坪花岗斑岩岩体位于扬子陆块的西南缘,处于鲜水河-小江碱性岩带和金沙江-哀牢山富碱斑岩带之间。其主量元素具有高碱,高Na2O/K2O值,低TiO2特征,属于高钾钙碱性系列岩石。微量元素富集LILE,LREE和过渡金属元素(Cu、Ni、Co),具有明显的“Ta-Nb-Ti"负异常,Eu负异常不明显。锆石LA-ICP-MS U-Pb年龄表明该区岩石的结晶年龄为(37.39±0.33) Ma。εHf(t)值为-1.8~+1.8,两阶段模式年龄为996~1 226 Ma。该区岩石具有较低的εNd(t)值（-7.4~-3.6）,较高的(87Sr/86Sr)i比值（0.706 077~0.706 231）,以及具有造山带铅特征的207Pb/204Pb值（15.567~15.574）和208Pb/204Pb值（38.321~38.335）。对银厂坪岩体的元素地球化学以及Sr-Nd-Pb-Hf同位素组成特征分析研究认为,研究区的花岗斑岩形成于近似大陆弧环境,同位素地球化学属于EMI-EMII过渡型源区,岩体形成于壳幔混合层。银厂坪岩体的地球化学属性更靠近安宁河碱性岩带,是该带分异末端的酸性端员组分。  相似文献   

16.
The Kalaxiange’er porphyry copper ore belt is situated in the eastern part of the southern Altai of the Central Asian Orogenic Belt and forms part of a broad zone of Cu porphyry mineralization in southern Mongolia, which includes the Oyu Tolgoi ore district and other copper–gold deposits. The copper ore bodies are spatially associated with porphyry intrusions of granodiorite, quartz diorite, quartz syenite, and quartz monzonite and have a polygenetic (polychromous) origin (magmatic porphyry, hydrothermal, and supergene). The mineralized porphyries are characterized by almost identical REE and trace element patterns. The Zr/Hf and Nb/Ta ratios are similar to those of normal granite produced through the evolution of mantle magma. The low initial Sr isotope ratio ISr, varying within a narrow range of values (0.703790–0.704218), corresponds to that of primitive mantle, whereas the εNd(T) value of porphyry varies from 5.8 to 8.4 and is similar to that of MORB. These data testify to the upper-mantle genesis of the parental magmas of ore-bearing porphyry, which were then contaminated with crustal material in an island-arc environment. The isotopic composition of sulfur (unimodal distribution of δ34S with peak values of − 2 to − 4‰) evidences its deep magmatic origin; the few lower negative δ34S values suggest that part of S was extracted from volcanic deposits later. The isotopic characteristics of Pb testify to its mixed crust–upper-mantle origin. According to SHRIMP U–Pb geochronological data for zircon from granite porphyry and granodiorite porphyry, mineralization at the Xiletekehalasu porphyry Cu deposit formed in two stages: (1) Hercynian “porphyry” stage (375.2 ± 8.7 Ma), expressed as the formation of porphyry with disseminated and vein–disseminated mineralization, and (2) Indosinian stage (217.9 ± 4.2 Ma), expressed as superposed hydrothermal mineralization. The Re–Os isotope data on molybdenite (376.9 ± 2.2 Ma) are the most consistent with the age of primary mineralization at the Xiletekehalasu porphyry Cu deposit, whereas the Ar–Ar isotopic age (230 ± 5 Ma) of K-feldspar–quartz vein corresponds to the stage of hydrothermal mineralization. The results show that mineralization at the Xiletekehalasu porphyry Cu deposit was a multistage process which resulted in the superposition of the Indosinian hydrothermal mineralization on the Hercynian porphyry Cu mineralization.  相似文献   

17.
秦岭显生宙地幔组成及其演化   总被引：2，自引：1，他引：2  
通过对秦岭造山带及扬子克拉通北缘显生宙时期 3个含地幔捕虏体的煌斑岩、钾镁煌斑岩、碱性玄武岩以及 11个不含捕虏体的辉石岩、辉长岩、玄武岩出露点的岩石地球化学对比研究 ,揭示出研究区地幔演化经历了自古生代的OIB亏损地幔到中生代的高度富集地幔再到中生代末期 -新生代的OIB MORB的亏损地幔的两次明显变更。制约这种变更的主要因素是熔融岩浆时源区发生的层圈相互作用类型。鉴于大陆岩石圈软流层体系的特征 ,有必要划分出岩石圈 /软流层相互作用带(过渡带 ) ,它是大陆岩浆作用的重要源区。  相似文献   

18.
藏南冈底斯带中新世斑岩成因主要存在残留洋壳的部分熔融、加厚下地壳的部分熔融、陆下岩石圈的部分熔融和俯冲流体交代基性下地壳的部分熔融四种观点.为了进一步阐明该时期的岩浆成因和大地构造背景,对冈底斯带甲玛矿区不同类型的斑岩体进行了岩石学分析和LA-ICP-MS锆石U-Pb测试,并运用X荧光光谱仪和电感耦合等离子体质谱仪分别对样品进行了全岩主、微量元素测试.测试结果显示冈底斯带甲玛矿区的斑岩类形成于16.7~14.4 Ma,总体上具有埃达克质岩石的地球化学特征.其中花岗斑岩类来自于藏南加厚的基性新生下地壳的部分熔融,而辉长闪长玢岩来源于富集的岩石圈地幔.早中新世以来（18~13 Ma）青藏高原处于构造转换阶段,含矿的埃达克质岩浆沿断裂通道上升,并且在上升过程中遭受到了中上地壳物质的混染,演化形成甲玛矿区内石英闪长玢岩、花岗闪长斑岩、二长花岗斑岩和花岗斑岩,而近乎同时期来自于岩石圈地幔的岩浆则演化形成辉长闪长玢岩;矿区内含矿热液流体在岩浆热驱动和构造应力作用下,在林布宗组砂板岩、角岩与多底沟组大理岩、灰岩的层间滑脱带或褶皱的构造虚脱空间就位,形成冈底斯带甲玛矽卡岩型铜多金属主矿体.   相似文献   

19.
《International Geology Review》2012,54(15):1835-1864
The Yinshan deposit is a large epithermal-porphyry polymetallic deposit, and the timing and petrogenesis of ore-hosting porphyries have been hotly debated. We present new results from geochemical, whole-rock Sr–Nd and zircon U–Pb–Hf–O isotopic investigations. Zircon U–Pb data demonstrate that the quartz porphyry, dacitic porphyry, and quartz dioritic porphyry formed at ?172.2 ± 0.4 Ma, ?171.7 ± 0.5 Ma, and ?170.9 ± 0.3 Ma, respectively. Inherited zircon cores show significant age spreads from ?730 to ?1390 Ma. Geochemically, they are high-K calc-alkaline or shoshonitic rocks with arc-like trace element patterns. They have similar whole-rock Nd and zircon Hf isotopic compositions, yet an increasing trend in ?Nd(t) and ?Hf(t) values typifies the suite. Older (inherited) zircons of the three porphyries display Hf compositions comparable to those of the Jiangnan Orogen basement rocks. In situ zircon oxygen isotopic analyses reveal that they have similar oxygen isotopic compositions, which are close to those of mantle zircons. Moreover, a decreasing trend of δ18O values is present. We propose that the ore-related porphyries of the Yinshan deposit were emplaced contemporaneously and derived from partial melting of Neoproterozoic arc-derived mafic (or ultra-mafic) rocks. Modelling suggests that the quartz porphyries, dacitic porphyries, and quartz dioritic porphyries experienced ?25%, ?10%, and ?10% crustal contaminations by Shuangqiaoshan rocks. Our study provides important constraints on mantle–crust interaction in the genesis of polymetallic mineralization associated with Mesozoic magmatism in southeastern China.  相似文献   

20.
西藏青草山Cu-Au矿床是班公湖-怒江缝合带北侧新发现的具有大型远景的斑岩型矿床,但该矿床含矿斑岩的年龄、成因及源区一直未得到有效的约束.对青草山花岗闪长岩以及含矿花岗岩闪长斑岩进行了锆石年代学、Hf同位素以及岩石地球化学研究.结果显示,花岗闪长岩与含矿花岗闪长斑岩的侵入时代分别为131.2±0.3 Ma与117.9±0.8 Ma,代表了班公湖-怒江缝合带早期的成岩作用以及斑岩Cu-Au成矿作用.二者具有相似的地球化学特征,表明二者可能具有相同的岩浆源区,是不同时期同源岩浆活动的产物.结合含矿花岗闪长斑岩锆石Hf同位素组成,认为青草山含矿斑岩形成于班公湖-怒江洋壳向北俯冲过程中,是下地壳部分熔融的产物,受到了少量地幔物质的混合.   相似文献   

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