廣東長埔錫多金屬礦床石英斑巖鋯石U-Pb年代學(xué)、Hf同位素組成及其地質(zhì)意義

丘增旺, 王 核, 閆慶賀, 李莎莎, 汪禮明, 卜 安, 慕生祿, 李 沛, 魏小鵬

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廣東長埔錫多金屬礦床石英斑巖鋯石U-Pb年代學(xué)、Hf同位素組成及其地質(zhì)意義

丘增旺1,2, 王 核1*, 閆慶賀1,2, 李莎莎1,2, 汪禮明3, 卜 安4, 慕生祿1,2, 李 沛1,2, 魏小鵬1,2

(1. 中國科學(xué)院 廣州地球化學(xué)研究所 礦物學(xué)與成礦學(xué)重點(diǎn)實(shí)驗(yàn)室, 廣東 廣州 510640; 2. 中國科學(xué)院大學(xué), 北京 100049; 3. 廣東省 有色金屬地質(zhì)局, 廣東 廣州 510060; 4. 廣東省有色金屬地質(zhì)局九三一隊(duì), 廣東 汕頭 515041)

廣東省海豐縣長埔錫多金屬礦床位于粵東地區(qū)蓮花山斷裂帶南西段, 是一個(gè)中型錫多金屬礦床。以與長埔錫多金屬礦床礦化聯(lián)系密切的石英斑巖為研究對(duì)象, 首次對(duì)其進(jìn)行了LA-ICP-MS鋯石U-Pb定年以及鋯石Hf同位素分析, 獲得其鋯石U-Pb同位素加權(quán)平均年齡為(145.0±0.9) Ma, 形成于早白堊世初; 鋯石Hf同位素特征顯示其Hf()為–7.95~ –2.74, 二階段模式年齡(DM2)為1371~1704 Ma, 表明石英斑巖主要來源于中元古代古老地殼巖石的部分熔融, 可能有少量地幔物質(zhì)的加入。根據(jù)所得數(shù)據(jù), 結(jié)合區(qū)域構(gòu)造演化, 長埔錫多金屬礦床石英斑巖可能形成于古太平洋板塊向歐亞大陸俯沖作用有關(guān)的區(qū)域伸展動(dòng)力學(xué)背景。

鋯石U-Pb年齡; Hf同位素; 石英斑巖; 長埔錫多金屬礦床; 廣東省

0 引 言

華南地區(qū)以大規(guī)模發(fā)育與花崗質(zhì)巖石有關(guān)的鎢錫多金屬礦床而著名。其中, 在華南內(nèi)陸, 特別是在南嶺及其鄰區(qū), 鎢錫礦床多呈爆發(fā)式集中產(chǎn)于160~150 Ma之間, 例如芙蓉, 荷花坪和錫田錫多金屬礦床, 窯嶺、淘錫坑和漂塘鎢礦床; 此外, 在南嶺西南側(cè)的右江盆地中, 也發(fā)育了與花崗質(zhì)侵入體有關(guān)的錫(鎢)礦床, 這些礦床主要產(chǎn)于100~80 Ma, 例如個(gè)舊、大廠和都龍錫多金屬礦床, 這些地區(qū)的礦床都得到了國內(nèi)外學(xué)者的廣泛關(guān)注[1–6]。位于南嶺東南面的粵東地區(qū), 區(qū)內(nèi)錫(鎢、銅)多金屬礦床(點(diǎn))星羅棋布, 亦是我國東部錫、鎢、銅、鉛、鋅、銀等多金屬礦產(chǎn)重要基地(圖1), 然而其研究程度遠(yuǎn)不及華南其他地區(qū)。

粵東地區(qū)廣泛發(fā)育與中生代火山-侵入雜巖密切相關(guān)的錫(鎢、銅)多金屬礦床, 例如長埔、塌山、金坑、厚婆坳、西嶺錫多金屬礦床, 蓮花山斑巖型鎢礦等[7]。與南嶺及其鄰區(qū)錫鎢多金屬礦床(以下簡稱為“南嶺區(qū)礦床”)相比, 存在明顯區(qū)別: 粵東地區(qū)錫鎢多金屬礦床(以下簡稱為“粵東區(qū)礦床”)主要的伴生元素是Cu、Pb、Zn、Au、Ag等, 而南嶺區(qū)礦床主要是W、Sn、Mo、Bi等; 粵東區(qū)礦床與次火山巖-侵入巖有關(guān), 而南嶺區(qū)礦床則主要與花崗質(zhì)侵入體有關(guān); 粵東區(qū)礦床主要形成于145~135 Ma, 而南嶺區(qū)礦床主要集中形成于160~150 Ma之間[8–19](表1)。然而, 對(duì)粵東地區(qū)礦床成巖成礦年代學(xué)、礦床地球化學(xué)等方面的研究卻極其有限。因此, 加強(qiáng)本區(qū)錫鎢多金屬礦床與華南其他地區(qū)礦床的對(duì)比研究, 顯得尤為有意義。

粵東海豐縣長埔錫多金屬礦床位于蓮花山斷裂帶南西側(cè), 是一中型熱液脈型錫多金屬礦床, 與石英斑巖密切相關(guān)[8,20]。該礦床自1958年發(fā)現(xiàn)以來, 許多地質(zhì)工作者對(duì)其進(jìn)行過研究, 但由于受當(dāng)時(shí)分析測試手段的限制, 在石英斑巖年代學(xué)等方面缺乏精確的數(shù)據(jù)。本文首次對(duì)長埔礦區(qū)石英斑巖進(jìn)行LA-ICP-MS鋯石U-Pb定年、鋯石Hf同位素分析, 從而進(jìn)一步探討其成巖年齡、物質(zhì)來源和成巖成礦地球動(dòng)力學(xué)背景。

1 區(qū)域地質(zhì)背景

粵東地區(qū)位于EW向南嶺巖漿構(gòu)造帶東南部與NE向東南沿海巖漿巖帶西南部的交匯部位[21], 區(qū)內(nèi)出露的地層主要包括上三疊統(tǒng)小坪組和下侏羅統(tǒng)金雞組沉積巖, 上侏羅統(tǒng)高基坪群火山巖以及下白堊統(tǒng)官草湖群火山碎屑紅層盆地沉積, 其中前三者是本區(qū)主要的賦礦層位。區(qū)內(nèi)構(gòu)造主要以NE、NW向?yàn)橹? EW向構(gòu)造局部斷續(xù)出現(xiàn)。其中, NE向構(gòu)造以3條區(qū)域性北東向斷裂帶, 自西向東為蓮花山斷裂帶(海豐-大埔斷裂帶)、普寧-潮州斷裂帶、惠來-饒平斷裂帶, 構(gòu)成西部長埔-八鄉(xiāng)、中部西嶺-厚婆坳和東部鐘丘洋-蓮花山3個(gè)平行的金屬成礦帶[7](圖1)。區(qū)內(nèi)中生代巖漿活動(dòng)十分強(qiáng)烈, 形成了大量的火山-侵入巖, 巖漿活動(dòng)以晚侏羅世最強(qiáng), 其次為早白堊世, 早中侏羅世較弱, 而晚白堊世僅有少量出露[22]。其中,花崗巖主要為二長花崗巖和黑云母花崗巖, 同位素年齡在170~89 Ma之間, 兩者與早、晚兩期成礦密切相關(guān), 二長花崗巖類等時(shí)年齡峰值為145 Ma左右; 晚期黑云母花崗巖等時(shí)線年齡峰值為139 Ma左右[23]。區(qū)內(nèi)火山巖為一套英安質(zhì)-流紋質(zhì)火山巖, 主要包括流紋巖、流紋英安巖、英安流紋巖及流紋質(zhì)和流紋英安質(zhì)凝灰?guī)r, 同位素年齡在175~110Ma之間[7]。徐曉春等將這些火山-侵入雜巖劃分為I-S過渡型巖石[24]。

圖1 粵東地區(qū)地質(zhì)略圖(據(jù)文獻(xiàn)[7]修改)

1. 第四系; 2. 晚侏羅世火山巖; 3. 上三疊統(tǒng)-下侏羅統(tǒng)沉積巖; 4. 中生代花崗巖; 5. 錫多金屬礦床(a. 云英巖型; b. 石英脈型; c. 硅酸鹽型; d. 硫化物型; 6. 鎢礦床); 7. 銅礦床; 8. 斷裂。

表1 粵東地區(qū)與南嶺地區(qū)錫鎢礦床成礦特征對(duì)比

2 礦床地質(zhì)背景

長埔礦區(qū)位于蓮花山斷裂帶南西段(圖1和圖2)。礦區(qū)出露地層為下侏羅統(tǒng)金雞組(J1j)碎屑巖和上侏羅統(tǒng)的高基坪組(J3j)火山巖, 為海陸交替變質(zhì)砂頁巖建造及酸性火山巖建造。區(qū)內(nèi)斷裂構(gòu)造發(fā)育, 方向主要為NE向, 其次為NW向。最主要構(gòu)造是NE向的層間滑動(dòng)構(gòu)造(如F1、F2), 以成礦前及成礦期的構(gòu)造活動(dòng)最為強(qiáng)烈, 以活動(dòng)的多期性、繼承性為其主要特點(diǎn), 與成礦關(guān)系最為密切, 是本礦床主要的成礦和控礦構(gòu)造, 并直接影響礦體的規(guī)模和形態(tài)。強(qiáng)烈的構(gòu)造作用, 致使區(qū)內(nèi)地層普遍片理化, 廣泛發(fā)育劈理和節(jié)理形成地區(qū)性的動(dòng)力變質(zhì)帶, 其中尤以一組傾向130°~155°, 傾角45°~60°的節(jié)理對(duì)成礦最為重要, 經(jīng)多次活動(dòng)張開, 充填了錫石石英脈、硫化物細(xì)脈以及無礦石英脈等, 是構(gòu)成細(xì)脈浸染型礦石的主要裂隙構(gòu)造。NW向斷裂如F31~F33規(guī)模僅次于NE向, 一般產(chǎn)狀與地層和礦體近于直交, 傾角很陡, 具張扭性特征, 多是成礦后構(gòu)造。區(qū)內(nèi)出露石英斑巖, 侵入于金雞組及上部高基坪組的地層之中。石英斑巖脈分布于整個(gè)礦區(qū), 以礦帶部位出現(xiàn)較多, 是礦區(qū)主要的脈巖組, 其產(chǎn)狀主要為層間侵入體也有成巖瘤狀或沿北東向緩斷層侵入的脈狀體, 產(chǎn)狀與礦體一致, 在空間上與礦體密切相關(guān)(圖2、圖3a和圖3b)。

礦區(qū)內(nèi)礦段可分為長埔段、樹林山段和田心段3個(gè)工業(yè)礦段, 其中以長埔段為主。各礦體皆呈層間脈狀產(chǎn)出, 礦體形態(tài)較簡單, 一般為似板狀、連續(xù)透鏡狀, 其次為透鏡狀、餅狀和充填脈狀。全區(qū)各礦體產(chǎn)狀基本一致, 傾向146°~153°, 傾角46°~56°。金屬礦物成分主要為錫石、黃鐵礦、磁黃鐵礦、閃鋅礦、方鉛礦、錳菱鐵礦等。脈石礦物主要包括石英、電氣石、綠泥石、絹云母等。礦石結(jié)構(gòu)主要有壓碎結(jié)構(gòu)、他形粒狀結(jié)構(gòu)和交代結(jié)構(gòu)。礦石構(gòu)造主要有角礫狀構(gòu)造、浸染裝構(gòu)造、塊狀構(gòu)造和細(xì)脈狀構(gòu)造。近礦圍巖蝕變的種類有電氣石化、硅化、綠泥石化、絹云母化、碳酸鹽化。

3 樣品和分析方法

用于鋯石U-Pb及Hf同位素分析的樣品采自長埔礦段V4礦脈旁側(cè)的石英斑巖(CP-5-1), 坐標(biāo)為115°15′23″E, 22°56′11″N, 石英斑巖手標(biāo)本呈灰白色, 斑狀結(jié)構(gòu), 塊狀構(gòu)造(圖3c), 斑晶主要為石英(10%~15%), 粒度為0.2~1.0 mm, 極少量的鉀長石(1%); 基質(zhì)為霏細(xì)結(jié)構(gòu), 主要為石英(70%~80%), 少量次生絹云母(5%) (圖3d)。

2.1 LA-ICP-MS 鋯石U-Pb定年

用于鋯石U-Pb年代學(xué)測試的樣品經(jīng)過人工破碎成約80目(0.177 mm), 將粉末用清水淘洗, 得到重砂部分, 再經(jīng)過電磁選分離出鋯石, 在雙目鏡下挑選出顆粒完整、無裂隙、透明度好的鋯石, 粘于環(huán)氧樹脂表面, 固化后打磨拋光至露出一個(gè)光潔平面然后進(jìn)行透反射和陰極發(fā)光(CL)照像, 結(jié)合這些圖像選擇適宜的測試點(diǎn)位及進(jìn)行合理的數(shù)據(jù)解釋。鋯石的微區(qū)原位U-Pb定年和微量元素分析在中國科學(xué)院廣州地球化學(xué)研究所同位素室國家重點(diǎn)實(shí)驗(yàn)室利用激光剝蝕電感耦合等離子體質(zhì)譜(LA-ICP-MS)完成。儀器采用美國Resonetics公司生產(chǎn)的RESOlution M-50激光剝蝕系統(tǒng)和Agilent 7500a型的ICP-MS聯(lián)機(jī)。用He作為剝蝕物質(zhì)的載氣。用美國國家標(biāo)準(zhǔn)技術(shù)研究院人工合成硅酸鹽玻璃標(biāo)準(zhǔn)參考物質(zhì)NIST610進(jìn)行儀器最佳化調(diào)試, 使儀器達(dá)到最佳的靈敏度、最小的氧化物產(chǎn)率(CeO/Ce<3%)和最低的背景值。實(shí)驗(yàn)采用標(biāo)準(zhǔn)鋯石TEMORA[26]作為測年外標(biāo), 所測元素激光斑束直徑為31 μm, 頻率為8 Hz。相關(guān)分析方法詳見文獻(xiàn)[27]。數(shù)據(jù)處理使用軟件ICPMSDataCal 10.1[28]。鋯石的諧和年齡圖繪制和年齡計(jì)算采用軟件Isoplot3.0[29]。

圖2 長埔礦區(qū)地質(zhì)略圖(據(jù)文獻(xiàn)[25]修改)

1. 第四系坡積洪積層; 2. 斷層; 3. 上侏羅統(tǒng)高基坪組火山巖; 4. 逆沖斷層; 5. 下侏羅統(tǒng)金雞組砂頁巖; 6. 產(chǎn)狀; 7. 石英斑巖脈; 8. 礦脈及編號(hào); 9. 河流; 10. 采樣位置。

圖3 長埔礦區(qū)石英斑巖與礦化的空間關(guān)系(a和b)、石英斑巖手標(biāo)本照片(c)及顯微鏡照片(d, 正交偏光, Q–石英)

2.2 鋯石Hf同位素分析

鋯石U-Pb年齡測試完畢后, 在中國科學(xué)院廣州地球化學(xué)研究所同位素國家重點(diǎn)實(shí)驗(yàn)室進(jìn)行Hf同位素原位分析, 使用儀器為美國Resonetics公司生產(chǎn)的Neptune Plus型多接受等離子質(zhì)譜儀(MC-ICP- MS), 激光剝蝕系統(tǒng)為RESOlution M-50, 詳細(xì)激光剝蝕參數(shù)如下: 分析時(shí)激光束斑直徑為45 μm, 前背景時(shí)間、激光剝蝕時(shí)間及沖掃時(shí)間分別為30 s、30 s和5 s, 頻率為8 Hz, 能量為80 mJ/cm2, 采用He和少量Ne作為氣體介質(zhì)。測試過程采用蓬萊鋯石作為標(biāo)樣[30], 數(shù)據(jù)標(biāo)準(zhǔn)化根據(jù)179Hf/177Hf =0.7325完成, 質(zhì)量歧視校正用指數(shù)法則進(jìn)行, Yb和Lu的干擾校正取176Lu/175Lu = 0.02655[31]和176Yb/172Yb =0.5887, 而Yb分餾校正則根據(jù)172Yb/173Yb =1.35272用指數(shù)法則進(jìn)行[32]。Hf值的計(jì)算采用176Lu的衰變常數(shù)為1.867×10–11 a–1 [33]。Hf()和Hf模式年齡計(jì)算中采用的球粒隕石和虧損地幔的176Hf/177Hf比值分別為0.282772[34]和0.28325[35], 二階段模式年齡計(jì)算中采用平均地殼的cc為–0.55[35]。

3 測試結(jié)果

3.1 LA-ICP-MS鋯石U-Pb定年

本文對(duì)石英斑巖(CP-5-1)中的鋯石進(jìn)行了U-Pb同位素分析, 其結(jié)果見表2。

表2 長埔石英斑巖LA-ICP-MS鋯石U-Pb測試結(jié)果

石英斑巖(CP-5-1)樣品中鋯石呈淺黃色—淺玫瑰色, 以多呈柱狀, 晶體粒徑一般為80~200 μm, 長短軸比大多為2∶1~4∶1。陰極發(fā)光圖像(圖4)揭示大部分鋯石具有清晰的巖漿韻律環(huán)帶, 裂紋不發(fā)育, 顯示巖漿成因特征[36]。石英斑巖(CP-5-1)樣品中鋯石的U含量為273.52~1835.67 μg/g, Th含量為159.52~955.77 μg/g, Th/U比值介于0.25~0.85之間, 平均0.56, 顯示出巖漿鋯石的特點(diǎn)[37–38]。

圖4 長埔石英斑巖鋯石代表性陰極發(fā)光圖像(CL)、分析點(diǎn)位、年齡及εHf(t)值

實(shí)線圓圈和虛線圓圈分別代表鋯石U-Pb及Hf同位素分析點(diǎn)位置。

U-Pb analysis spots are shown by solid circles, and Hf isotope analysis spots are shown by dashed circles.

石英斑巖(CP-5-1)樣品中鋯石共測定30個(gè)點(diǎn), 其中15、25、27號(hào)點(diǎn)由于測試異常已刪去, 剩余點(diǎn)在一致曲線中成群分布, 具有非常一致的年齡, 變化于(143.5±1.8) Ma~(146.6±2.6) Ma之間,206Pb/238U加權(quán)平均值年齡為(145.0±0.9) Ma, MSWD = 0.10(圖5a), 為石英斑巖的侵位結(jié)晶年齡。結(jié)合近來發(fā)表的數(shù)據(jù)[39–43]，得到粵東地區(qū)巖漿巖年齡分布直方圖如圖5b所示。

3.2 鋯石Hf同位素

對(duì)花崗斑巖鋯石U-Pb年齡測點(diǎn)進(jìn)行原位Hf同位素分析結(jié)果見表3, Hf同位素演化圖解如圖6a所示。石英斑巖鋯石的176Lu/177Hf值大部分小于0.002, 表明鋯石在形成后具有較低的放射性成因Hf積累, 因而可以用初始176Lu/177Hf比值代表鋯石形成時(shí)的176Lu/177Hf比值[44]?；◢彴邘r初始176Hf/177Hf比值介于0.282459~0.282608之間,Hf()值為–7.95~ –2.74, 二階段模式年齡(DM2)為1371~1704 Ma。

圖5 長埔石英斑巖鋯石U-Pb諧和圖(a)及粵東地區(qū)巖漿巖年齡分布直方圖(b, 長埔石英斑巖年齡為本文數(shù)據(jù), 其余數(shù)據(jù)收集自文獻(xiàn)[39–43], 見表4)

表3 長埔礦區(qū)石英斑巖鋯石Lu-Hf同位素分析結(jié)果

圖6 長埔石英斑巖εHf(t)-年齡圖解(a)及粵東巖漿巖tDM2頻率分布直方圖(b)

(a) 背景數(shù)據(jù)引自文獻(xiàn)[39–41,43]; (b) 數(shù)據(jù)引自本文及文獻(xiàn)[39–41,43] (表4)。

In figure a, the data of volcanic and intrusive rocks in eastern Guangdong are from references [39–41,43]. In figure b, the data ofDM2for magmatic rocks from eastern Guangdong are from this study and references [39–41,43] (Table 4).

4 討 論

4.1 成巖年齡及意義

前人曾對(duì)長埔礦區(qū)石英斑巖開展過同位素定年工作, 謝華光等[25]對(duì)長埔錫礦的石英斑巖進(jìn)行全巖K-Ar同位素定年, 得到年齡為(143.7±3.5) Ma。K-Ar體系的抗擾動(dòng)性差, 加之封閉溫度很低(約(200±50) ℃)[45], 導(dǎo)致定年結(jié)果常低于巖體的實(shí)際年齡, 因此早期的測試方法很難獲得精確的成巖年齡。由于鋯石具有很高的封閉溫度(> 800 ℃), 其在后期熱液蝕變作用過程中能夠很好地保存封閉的同位素體系[46], 因此LA-ICP-MS鋯石U-Pb同位素定年方法能夠較好地獲得巖體的成巖時(shí)代。本文對(duì)長埔錫多金屬礦床石英斑巖進(jìn)行了鋯石LA-ICP-MS鋯石U-Pb同位素定年, 得到石英斑巖年齡為(145.0±0.9) Ma (圖5a), 屬于早白堊世初期的產(chǎn)物。

前人研究表明, 粵東地區(qū)及中國東南沿海中生代火山巖劃分為上下2個(gè)巖系4個(gè)旋回, 并有相應(yīng)的巖漿侵入, 形成大規(guī)模的火山-侵入雜巖[47–48]。對(duì)照其劃分方案, 蓮花山斷裂帶南西段廣泛發(fā)育的區(qū)內(nèi)上侏羅統(tǒng)高基坪群(英安巖-流紋巖組合)屬下巖系第Ⅱ旋回, 同位素年齡為157~148 Ma, 其稍后侵入的酸性花崗質(zhì)巖石, 年齡為155~136 Ma[48–50]。事實(shí)上, 通過對(duì)近期發(fā)表的年代學(xué)數(shù)據(jù)收集[39–43](表4), 我們發(fā)現(xiàn)粵東地區(qū)巖漿活動(dòng)主要集中在2個(gè)時(shí)期: 早白堊世初期(150~134 Ma)和中晚侏羅世(170~154 Ma) (圖5b), 因而長埔礦區(qū)的石英斑巖正是早白堊世巖漿活動(dòng)的產(chǎn)物, 與東南沿海第Ⅱ旋回巖漿活動(dòng)有關(guān)。

4.2 巖漿源區(qū)特征

研究表明, 鋯石原位Hf同位素分析能夠很好地鑒別花崗巖漿的物質(zhì)來源[35,44]。長埔石英斑巖Hf()為–7.95~ –2.74, 均值為–5.88, 二階段模式年齡(DM2)為1371~1704 Ma。在Hf()-圖(圖6a)上, 全部樣品分布于球粒隕石及下地殼Hf同位素分異演化線之間, 表明長埔礦區(qū)石英斑巖主要來源于中元古代地殼結(jié)晶基底(圖6b)。盡管石英斑巖樣品中大部分鋯石的Hf()值呈現(xiàn)出負(fù)值, 但Hf()值和二階段模式年齡存在一定的變化范圍, 暗示物質(zhì)組分的不均一性, 表明在地殼物質(zhì)為主體的情況下, 可能有少量的新生地幔組分加入。如表4所示, Zhang.[40]的研究表明, 粵東地區(qū)主要的中晚侏羅世花崗質(zhì)巖石Hf()值為–7.2~ +3.9, 二階段模式年齡為962~2166 Ma; Guo.[43]對(duì)粵東中生代火山巖鋯石Hf同位素進(jìn)行研究, 得到中晚侏羅世火山巖Hf()值為–7.8 ~ +1.5, 二階段模式年齡為1219~1714 Ma, 早白堊世的火山巖Hf() 值為–7.7 ~ +2.3, 二階段模式年齡為1230~1688 Ma; 丘增旺等[39]得到陶錫湖錫多金屬礦床早白堊世花崗斑巖Hf()值為–10.5 ~ –5.9, 二階段模式年齡為1566~ 1863 Ma; 劉鵬等[41]通過對(duì)田東鎢錫礦床花崗質(zhì)巖石研究, 得到晚侏羅世的粗?；◢弾rHf()值為–3.6 ~ –0.1, 二階段模式年齡為1217~1439 Ma, 早白堊世的細(xì)粒黑云母花崗巖Hf()值為–5.4 ~ –1.6, 二階段模式年齡為1330~1423 Ma。這些測試結(jié)果均表明, 長埔礦區(qū)石英斑巖Hf同位素組成與粵東地區(qū)的早白堊世巖漿巖類似。事實(shí)上, 粵東地區(qū)中晚侏羅世巖漿巖與早白堊世巖漿巖Hf同位素組成亦是比較一致, 均指示巖漿巖是主要在早中元古代下地殼部分熔融的基礎(chǔ)上, 加入了一定比例的地幔物質(zhì)混合而成的(圖6a和6b)。這個(gè)結(jié)論也得到了前人對(duì)粵東火山-侵入巖Sr-Nd-Pb同位素分析結(jié)果的支持[42,51]。

表4 粵東巖漿巖鋯石U-Pb年齡及Hf同位素組成

4.3 構(gòu)造背景

當(dāng)前, 學(xué)術(shù)界對(duì)于華南地區(qū)中生代巖漿-構(gòu)造-成礦機(jī)制存在不同見解, 提出了許多模型用以解釋構(gòu)造-巖漿-成礦作用, 例如: (1)古太平洋板塊俯沖角度由緩變陡[52–53]; (2)古太平洋平俯沖模型[54–55]; (3)多階段巖石圈伸展模型[56]; (4)陸內(nèi)裂谷伸展[57–58]; (5)古太平洋板塊傾斜俯沖[59]; (6)洋中脊俯沖模型[60–61]。由于與伸展有關(guān)的成礦和巖漿作用均呈多期幕式爆發(fā)出現(xiàn), 因而巖石圈多階段伸展模型可能更好解釋其形成機(jī)制[56]。

區(qū)域巖石圈伸展可能開始于早中侏羅世[1,3,56,62], 而峰值主要集中在180~155 Ma、145~125 Ma和110~ 75 Ma三個(gè)階段, 而145~125 Ma階段的伸展作用很可能是由于太平洋板塊俯沖方向改變引發(fā)的[56,63]。徐曉春等[24,49]通過對(duì)粵東地區(qū)中生代火山-侵入巖研究, 得出本區(qū)在晚侏羅世-早白堊世具有從活動(dòng)大陸邊緣向后造山伸展環(huán)境轉(zhuǎn)變的特征。筆者對(duì)同處蓮花山斷裂帶上陶錫湖錫多金屬礦床及金坑錫多金屬礦床的花崗斑巖((141.8±1.0)Ma)和細(xì)?；◢弾r((141.1± 0.8)Ma)地球化學(xué)特征研究表明, 兩者均產(chǎn)于后碰撞伸展動(dòng)力學(xué)背景(圖7)。此外, 據(jù)丘元禧等[66]研究表明, 燕山期以來, 蓮花山斷裂帶經(jīng)歷過3期變形變質(zhì)事件, 其中, 在晚侏羅世-早白堊世早期, 發(fā)生了強(qiáng)烈的左行剪切, 同時(shí)由于地殼隆升而逐步伸展, 沿蓮花山斷裂帶有大規(guī)模的中酸性火山噴溢和花崗質(zhì)巖漿的侵入, 而長埔礦區(qū)石英斑巖正是該期構(gòu)造-巖漿事件的產(chǎn)物, 形成于地殼隆升而引發(fā)的拉張環(huán)境下。

圖7 陶錫湖花崗斑巖及金坑細(xì)粒花崗巖Rb-(Y+Nb)圖解(a, 據(jù)Pearce[64])和R2-R1圖解(b, 據(jù)Batchelor et al.[65])構(gòu)造環(huán)境判別圖(陶錫湖花崗斑巖數(shù)據(jù)引自文獻(xiàn)[40], 金坑細(xì)?；◢弾r數(shù)據(jù)來自作者未發(fā)表數(shù)據(jù))

Syn-COLG–同碰撞花崗巖; VAG–火山弧花崗巖; WPG–板內(nèi)花崗巖; ORG–洋中脊花崗巖; post-COLG–后碰撞花崗巖。①地幔斜長花崗巖; ②破壞性活動(dòng)板塊邊緣(板塊碰撞前)花崗巖; ③板塊碰撞后隆起期花崗巖; ④晚造山期花崗巖; ⑤非造山A型花崗巖; ⑥同碰撞(S型)花崗巖; ⑦造山期后A型花崗巖。

syn-COLG – syn-collision granite; VAG – volcanic-arc granite; WPG – within-plate granite; ORG – ocean-ridge granite; post-COLG – post-collision granite. ① mantle-derived granite; ② pre-plate-collision granite; ③ post-collisional-uplift granite; ④ late-orogenic granite; ⑤ anorogenic granite;⑥ syn-collisional granite; ⑦ post-orogenic granite.

5 結(jié) 論

(1) 長埔錫多金屬礦床石英斑巖LA-ICP-MS鋯石U-Pb年齡為(145.0±0.9) Ma, 屬于早白堊世初期巖漿作用的產(chǎn)物。

(2) 石英斑巖鋯石Hf同位素特征表明, 其巖漿源區(qū)主要來自于地殼, 并伴隨有少量地幔物質(zhì)的加入。

(3) 長埔錫多金屬礦床石英斑巖形成于古太平洋板塊向歐亞板塊俯沖所引起的巖石圈伸展的構(gòu)造背景, 是大陸巖石圈大面積伸展背景下的產(chǎn)物。

感謝兩位審稿人對(duì)本文提出的建設(shè)性的意見！鋯石U-Pb和Hf同位素測試分別得到中國科學(xué)院廣州地球化學(xué)研究所李聰穎博士和張樂助理研究員的幫助; 野外工作得到廣東省有色金屬地質(zhì)局九三一隊(duì)同行的大力支持, 在此一并表示感謝！

[1] 華仁民, 陳培榮, 張文蘭, 陸建軍. 論華南地區(qū)中生代3次大規(guī)模成礦作用[J]. 礦床地質(zhì), 2005, 24(2): 99–107.Hua Ren-min, Chen Pei-rong, Zhang Wen-lan, Lu Jian-jun. Three major metallogenic events in Mesozoic in South China [J]. Mineral Deposits, 2005, 24(2): 99–107 (in Chinese with English abstract).

[2] 華仁民, 李光來, 張文蘭, 胡東泉, 陳培榮, 陳衛(wèi)鋒, 王旭東. 華南鎢和錫大規(guī)模成礦作用的差異及其原因初探[J]. 礦床地質(zhì), 2010, 29(1): 9–23.Hua Ren-min, Li Guang-lai, Zhang Wen-lan, Hu Dong-quan, Chen Pei-rong, Chen Wei-feng, Wang Xu-dong. A tentative discussion on differences between large-scale tungsten and tin mineralizations in South China [J]. Mineral Deposits, 2010, 29(1): 9–23 (in Chinese with English abstract).

[3] 毛景文, 謝桂青, 郭春麗, 袁順達(dá), 程彥博, 陳毓川. 華南地區(qū)中生代主要金屬礦床時(shí)空分布規(guī)律和成礦環(huán)境[J]. 高校地質(zhì)學(xué)報(bào), 2008, 14(4): 510–526.Mao Jing-wen, Xie Gui-qing, Guo Chun-li, Yuan Shun-da, Cheng Yan-bo, Chen Yu-chuan. Spatial-temporal distribution of Mesozoic ore deposits in South China and their metallogenic settings [J]. Geol J China Univ, 2008, 14(4): 510–526 (in Chinese with English abstract).

[4] Hu R Z, Zhou M F. Multiple Mesozoic mineralization events in South China — An introduction to the thematic issue [J]. Min Deposit, 2012, 47(6): 579–588.

[5] Mao J W, Cheng Y B, Chen M H, Pirajno F. Major types and time-space distribution of Mesozoic ore deposits in South China and their geodynamic settings [J]. Min Deposit, 2013, 48(3): 267–294.

[6] 陳毓川, 王登紅, 徐志剛, 黃凡. 華南區(qū)域成礦和中生代巖漿成礦規(guī)律概要[J]. 大地構(gòu)造與成礦學(xué), 2014, 38(2): 219– 229.Chen Yu-chuan, Wang Deng-hong, Xu Zhi-gang, Huang Fan. Outline of regional metallogeny of ore deposits associated with the Mesozoic magmatism in South China [J]. Geotecton Metallogen, 2014, 38(2): 219–229 (in Chinese with English abstract).

[7] 徐曉春, 岳書倉. 粵東錫(鎢、銅)多金屬礦床的成礦物質(zhì)來源和成礦作用[J]. 地質(zhì)科學(xué), 1999, 34(1): 81–92.Xu Xiao-chun, Yue Shu-cang. Source material and metallization of tin (tungsten, copper) polymetallic deposits in eastern Guangdong Province [J]. Sci Geol Sinica, 1999, 34(1): 81–92 (in Chinese with English abstract).

[8] 戚建中, 黃賓. 粵東長埔-西嶺地區(qū)錫礦斷裂巖漿控制因素及成礦模式[J]. 中國地質(zhì)科學(xué)院南京地質(zhì)礦產(chǎn)研究所刊, 1988, 9(4): 76–94.Qi Jian-zhong, Huang Bin. Fault-magmatic control of tin mineralization in Changpu-Xiling region, east Guangdong, and regional model [J]. Bull Nanjing Inst Geol Mineral Resour, 1988, 9(4): 76–94 (in Chinese with English abstract).

[9] 沈渭洲, 凌洪飛. 巖背和塌山含錫花崗斑巖的同位素地球化學(xué)特征和物質(zhì)來源[J]. 地球?qū)W報(bào), 1994, 15(1): 117–123. Shen Wei-zhou, Ling Hong-fei. Isotopic geochemiscal characteristics and material sources of tin-bearing granite porphyry in Yanbei and Tashan [J]. Acta Geosci Sinica, 1994, 15(1): 117–123 (in Chinese with English abstract).

[10] 徐曉春. 粵東地區(qū)中生代巖漿作用和金屬成礦的地球化學(xué)研究[D]. 合肥: 合肥工業(yè)大學(xué), 1993. Xu Xiao-chun. Geochemical studies on the Mesozoic magmatic and metallization, Eastern Guangdong Province, China [D]. Hefei: Hefei University of Technology, 1993 (in Chinese with English abstract).

[11] 滿發(fā)勝, 白玉珍, 倪守斌, 黎彤. 蓮花山鎢礦床同位素地質(zhì)學(xué)初步研究[J]. 礦床地質(zhì), 1983, 2(4): 35–42.Man Fa-sheng, Bai Yu-zhen, Ni Shou-bin, Li Tung. Preliminary isotope studies of the Lianhuashan tungsten ore deposit [J]. Mineral Deposits, 1983, 2(4): 35–42 (in Chinese with English abstract).

[12] 倪守斌, 滿發(fā)勝, 白玉珍, 黎彤. 蓮花山鎢礦區(qū)Rb-Sr同位素地質(zhì)年齡[J]. 中國科學(xué)技術(shù)大學(xué)學(xué)報(bào), 1983, 13(2): 246– 252.Ni Shou-bin, Man Fa-sheng, Bai Yu-zhen, Li Tung. Rb-Sr ages of rocks in Lianhuashan mining region [J]. J China Univ Sci Technol, 1983, 13(2): 246–252 (in Chinese with English abstract).

[13] 張文蘭, 華仁民, 王汝成, 李惠民, 屈文俊, 季建清. 贛南漂塘鎢礦花崗巖成巖年齡與成礦年齡的精確測定[J]. 地質(zhì)學(xué)報(bào), 2009, 83(5): 659–670. Zhang Wen-lan, Hua Ren-min, Wang Ru-cheng, Li Hui-min, Qu Wen-jun, Ji Jian-qing. New dating of the Piaotang granite and related tungsten mineralization in southern Jiangxi [J]. Acta Geosci Sinica, 2009, 83(5): 659–670 (in Chinese with English abstract).

[14] 劉義茂, 戴橦謨, 盧煥章, 胥友志, 王昌烈, 康衛(wèi)清. 千里山花崗巖成巖成礦的40Ar-39Ar和Sm-Nd同位素年齡[J]. 中國科學(xué)(D輯), 1997, 27(5): 425–430.Liu Yimao, Dai Tongmo, Lu Huanzhang, Xu Youzhi, Wang Changlie, Kang Weiqing. The40Ar-39Ar and Sm-Nd isotopic dating for the Qianlishan granite and its associated mineralizaitons [J]. Sci China (D), 1997, 27(5): 425–430 (in Chinese).

[15] 李紅艷, 毛景文, 孫亞利, 鄒曉秋, 何紅蓼, 杜安道. 柿竹園鎢多金屬礦床的Re-Os同位素等時(shí)線年齡研究[J]. 地質(zhì)論評(píng), 1996, 42(3): 261–267.Li Hong-yan, Mao Jing-wen, Sun Ya-li, Zheng Xiao-qiu, He Hong-liao, Du An-dao. Re-Os isotopic chronology of molybdenites in the Shizhuyuan polymetallic tungsten deposit, Southern Hunan [J]. Geol Rev, 1996, 42(3): 261–267 (in Chinese with English abstract).

[16] 毛景文, 李曉峰, Lehmann B, 陳文, 藍(lán)曉明, 魏紹六. 湖南芙蓉錫礦床錫礦石和有關(guān)花崗巖的40Ar-39Ar年齡及其地球動(dòng)力學(xué)意義[J]. 礦床地質(zhì), 2004, 23(2): 164–175.Mao Jing-wen, Li Xiao-feng, Lehmann B, Chen Wen, Lan Xiao-ming, Wei Shao-liu.40Ar-39Ar dating of tin ores and related granite in Furong tin orefield, Hunan Province and its geodynamic significance [J]. Mineral Deposits, 2004, 23(2): 164–175 (in Chinese with English abstract).

[17] 翟偉, 孫曉明, 鄔云山, 孫紅英, 華仁民, 李文鉛. 粵北瑤嶺鎢礦成礦相關(guān)花崗巖的鋯石SHRIMP年齡與40Ar/39Ar成礦年齡及其地質(zhì)意義[J]. 礦床地質(zhì), 2011, 30(1): 21–32.Zhai Wei, Sun Xiao-ming, Wu Yun-shan, Sun Hong-ying, Hua Ren-min, Li Wen-qian.40Ar-39Ar dating of Yaoling tungsten deposit in northern Guangdong Province and SHRIMP U-Pb zircon age of related granites [J]. Mineral Deposits, 2011, 30(1): 21–32 (in Chinese with English abstract).

[18] 顧晟彥, 華仁民, 戚華文. 廣西姑婆山花崗巖單顆粒鋯石LA-ICP-MS U-Pb定年及全巖Sr-Nd同位素研究[J]. 地質(zhì)學(xué)報(bào), 2006, 80(4): 543–553.Gu Sheng-yan, Hua Ren-min, Qi Hua-wen. Study on zircon LA-ICP-MS U-Pb dating and Sr-Nd isotope of the Guposhan granite in Guangxi [J]. Acta Geol Sinica, 2006, 80(4): 543–553 (in Chinese with English abstract).

[19] 康志強(qiáng), 馮佐海, 李曉峰, 廖家飛, 余勇, 潘會(huì)彬. 桂東北水巖壩鎢錫礦田白云母40Ar-39Ar年代學(xué)研究及其地質(zhì)意義[J]. 礦物巖石地球化學(xué)通報(bào), 2010, 21(6): 610–615. Kang Zhi-qiang, Feng Zuo-hai, Li Xiao-feng, Liao Jia-fei, Yu Yong, Pan Hui-bin.40Ar-39Ar age of muscovite in the Shuiyanba tungsten-tin ore field in Northeast Guangxi and its geological significance [J]. Bull Mineral Petrol Geochem, 2010, 21(6): 610–615 (in Chinese with English abstract).

[20] 馬秀娟. 長埔錫礦床成礦流體性質(zhì)與演化[J].地球?qū)W報(bào), 1995, 16(4): 386–396. Ma Xiu-juan. The characters and evolution of metallogenic fluids of Changpu tin deposit [J]. Acta Geosci Sinica, 1995, 15(4): 386–396 (in Chinese with English abstract).

[21] 廣東省地質(zhì)礦產(chǎn)局. 廣東省區(qū)域地質(zhì)志[M]. 北京: 地質(zhì)出版社, 1988: 1–191. Guangdong Bureau of Geology and Mineral Resources. Regional Geology of Guangdong Province [M]. Beijing: Geological Publishing House, 1988: 1–191 (in Chinese with English abstract).

[22] 郭銳, 卜安. 粵東火山巖盆地銅-鉛-鋅多金屬礦床找礦新發(fā)現(xiàn)與認(rèn)識(shí)[J]. 礦產(chǎn)與地質(zhì), 2006, 20(3): 243–246. Guo Rui, Bu An. New discovery and understanding about seeking the copper-lead-zinc polymetallic deposits in volcanic basin of east Guangdong [J]. Mineral Resour Geol, 2006, 20(3): 243–245 (in Chinese with English abstract).

[23] 岳書倉, 雷新勇, 龔昌瑞, 徐曉春. 粵東花崗巖及錫、鎢礦床的地球化學(xué)研究[J]. 資源調(diào)查與環(huán)境, 1989, 10(1): 27– 41. Yue Shu-cang, Lei Xin-yong, Gong Chang-rui, Xu Xiao-chun. Geochemical studies on tin and tungsten deposits and granitoid in eastern Guangdong Province [J]. Resour Surv Environ, 1989, 10(1): 27–41 (in Chinese with English abstract).

[24] 徐曉春, 岳書倉. 粵東地區(qū)中生代火山巖與侵入巖的成因關(guān)系及成因類型[J]. 合肥工業(yè)大學(xué)學(xué)報(bào)(自然科學(xué)版), 1994, 17(4): 184–192. Xu Xiao-chun, Yue Shu-cang. Genetic relationship and type of the Mesozoic volcanic and intrusive rocks in eastern Guangdong, China [J]. J Hefei Univ Technol, 1994, 17(4): 184–192 (in Chinese with English abstract).

[25] 謝華光, 王文斌. 廣東長埔錫礦床的成礦特征及物質(zhì)來源[J].地質(zhì)找礦論叢, 1989, 4(3): 24–36.Xie Hua-guang, Wang Wen-bin. Metallogenic characteristics and substance source of Changpu tin deposit, Guangdong [J]. Contrib Geol Mineral Resour Res, 1989, 4(3): 24–36 (in Chinese with English abstract).

[26] Black L P, Kamo S L, Allen C M, Aleinikoff J N, Davis D W, Korsch R J, Foudoulis C. TEMORA 1: A new zircon standard for Phanerozoic U-Pb geochronology [J]. Chem Geol, 2003, 200(1): 155–170.

[27] 涂湘林, 張紅, 鄧文峰, 凌明星, 梁華英, 劉穎, 孫衛(wèi)東. RESOlution激光剝蝕系統(tǒng)在微量元素原位微區(qū)分析中的應(yīng)用[J]. 地球化學(xué), 2011, 40(1): 83–98.Tu Xiang-lin, Zhang Hong, Deng Wen-feng, Ling Ming-xing, Liang Hua-ying, Liu Ying, Sun Wei-dong. Application of RESOlutionlaser ablation ICP-MS in trace element analyses [J]. Geochimica, 2011, 40(1): 83–98 (in Chinese with English abstract).

[28] Liu Y S, Gao S, Hu Z C, Gao C G, Zong K Q, Wang D B. Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen: U-Pb dating, Hf isotopes and trace elements in zircons from mantle xenoliths [J]. J Petrol, 2010, 51: 537–571.

[29] Ludwig K R. User’s manual for Isoplot 3.00: A geochronological toolkit for Microsoft Excel [R]. Berkeley: Berkeley Geochronology Center Special Publication, 2003, 4(1): 1–71.

[30] Li X H, Long W G, Li Q L, Liu Y, Zheng Y F, Yang Y H, Chamberlain K R, Wan D F, Guo C H, Wang X C, Tao H. Penglai zircon megacrysts: A potential new working reference material for microbeam determination of Hf-O isotopes and U-Pb age [J]. Geostand Geoanal Res, 2010, 34(2): 117–134.

[31] Chu N C, Taylor R N, Chavagnac V, Nesbitt R W, Boella R M, Milton J A, German C, Bayon G, Burton K. Hf isotope ratio analysis using multi-collector inductively coupled plasma mass spectrometry: An evaluation of isobaric interference corrections [J]. J Anal Atom Spect, 2002, 17(12): 1567–1574.

[32] Wu F Y, Yang Y H, Xie L W, Yang J H, Xu P. Hf isotopic compositions of the standard zircons and baddeleyites used in U-Pb geochronology [J]. Chem Geol, 2006, 234(1/2): 105– 126.

[33] Scherer E, Munker C, Mezger K. Calibration of the lutetium-hafnium clock [J]. Science, 2001, 293(5530): 683–687.

[34] Blichert-Toft J, Albarede F. The Lu-Hf isotope geochemistry of chondrites and the evolution of the mantle crust system [J]. Earth Planet Sci Lett, 1997, 148(1/2): 243–258.

[35] Griffin W L, Wang X, Jackson S E, Pearson N J, O’Reilly S Y. Zircon geochemistry and magma mixing, SE China: In-situ analysis of Hf isotopes, Tonglu and Pingtan igneous complexes [J]. Lithos, 2002, 61(3/4): 237–269.

[36] Rubatto D, Gebauer D. Use of cathodoluminescence for U-Pb zircon dating by ion microprobe: Some examples from the Western Alps [M]. Pagel M, Barbin V, Blanc P, Ohnenstetter D. Cathodoluminescence in Geosciences. Berlin: Springer, 2000: 373–400.

[37] Belousova E A, Griffin W L, Suzanne Y, O’Reilly, Fisher N I. Igneous zircon: trace element composition as an indicator of source rock type [J]. Contrib Mineral Petrol, 2002, 143(5): 602–622.

[38] 吳元保, 鄭永飛. 鋯石成因礦物學(xué)研究及其對(duì)U-Pb年齡解釋的制約[J]. 科學(xué)通報(bào), 2004, 49(16): 1589–1604. Wu Yuanbao, Zheng Yongfei. The genesis of zircon and the constraints on the interpretation of U-Pb age [J]. Chinese Sci Bull, 2004, 49(16): 1589–1604 (in Chinese).

[39] 丘增旺, 王核, 汪禮明, 卜安, 李莎莎, 慕生祿, 李沛, 魏小鵬. 廣東陶錫湖錫多金屬礦床花崗斑巖鋯石U-Pb年代學(xué)、地球化學(xué)、Hf同位素組成及其地質(zhì)意義[J]. 大地構(gòu)造與成礦學(xué), 2016, 待刊.Qiu Zeng-wang, Wang He, Wang Li-ming, Bu An, Li Sha-sha, Mu Sheng-lu, Li Pei, Wei Xiao-peng. Zircon U-Pb geochronology, geochemistry and Lu-Hf isotopes of the granite porphyry in the Taoxihu tin polymetallic deposit, Guangdong Province, SE China and its geological significance [J]. Geotecton Metallogen, 2016, in Press (in Chinese with English abstract).

[40] Zhang Y, Yang J H, Sun J F, Zhang J H, Chen J Y, Li X H. Petrogenesis of Jurassic fractionated I-type granites in Southeast China: Constraints from whole-rock geochemical and zircon U-Pb and Hf-O isotopes [J]. J Asian Earth Sci, 2015, 111: 268–283.

[41] 劉鵬, 程彥博, 毛景文, 王小雨, 姚薇, 陳敘濤, 曾曉劍. 粵東田東鎢錫多金屬礦床花崗巖鋯石U-Pb年齡, Hf同位素特征及其意義[J]. 地質(zhì)學(xué)報(bào), 2015, 89(7): 1244–1257.Liu Peng, Cheng Yan-bo, Mao Jing-wen, Wang Xiao-yu, Yao Wei, Chen Xu-tao, Zeng Xiao-jian. Zircon U-Pb age and Hf isotopic characteristics of granite from the Tiandong W-Sn polymetallic deposit in Eastern Guangdong Province and its significance [J]. Acta Geol Sinica, 2015, 89(5): 1244–1257 (in Chinese with English abstract).

[42] 趙希林, 余明剛, 劉凱, 毛建仁, 葉海敏, 邢光福. 粵東地區(qū)早白堊世花崗質(zhì)巖漿作用及其成因演化[J]. 地質(zhì)論評(píng), 2012, 58(5): 965–977.Zhao Xi-lin, Yu Ming-gang, Liu Kai, Mao Jian-ren, Ye Hai-min, Xing Guang-fu. The magmtic and genetic evolution of Early Cretaceous granitoids in eastern Guangdong Province [J]. Geol Rev, 2012, 58(5): 965–977 (in Chinese with English abstract).

[43] Guo F, Fan W M, Li C W, Zhao L, Li H X, Yang J H. Multi-stage crust-mantle interaction in SE China: Temporal, thermal and compositional constraints from the Mesozoic felsic volcanic rocks in eastern Guangdong-Fujian provinces [J]. Lithos, 2012, 150: 62–84.

[44] 吳福元, 李獻(xiàn)華, 鄭永飛, 高山. Lu-Hf同位素體系及其巖石學(xué)應(yīng)用[J]. 巖石學(xué)報(bào), 2007, 23(2): 185–220.Wu Fu-yuan, Li Xian-hua, Zheng Yong-fei, Gao Shan. Lu-Hf isotopic systematicsand their applications in petrology [J]. Acta Petrol Sinica, 2007, 23(2): 185–220 (in Chinese with English abstract).

[45] 鄭永飛, 魏春生, 王崢嶸, 黃耀生, 張宏. 大龍山巖體冷卻史及其成礦關(guān)系的同位素研究[J]. 地質(zhì)科學(xué), 1997, 32(4): 465–477. Zheng Yong-fei, Wei Chun-sheng, Wang Zheng-rong, Huang Yao-sheng, Zhang Hong. An isotope study on the cooling history of the Dalongshan granite massif and its bearing on mineralization process [J]. Sci Geol Sinica, 1997, 32(4): 465–477(in Chinese with English abstract).

[46] Cherniak D J, Watson E B, Grove M, Harrison T M. Pb diffusion in monazite: A combined RBS/SIMS study [J]. Geochim Cosmochim Acta, 2004, 68(4): 829–840.

[47] 尹家衡, 黃光昭, 徐明華. 粵東中生代火山旋回劃分及對(duì)比[J]. 資源調(diào)查與環(huán)境, 1989, 10(4): 16–28.Yin Jia-heng, Huang Guang-zhao, Xu Ming-hua. Division and correlation of Mesozoic volcanic-cycles in east Guangdong [J]. Resour Surv Environ, 1989, 10(4): 16–28 (in Chinese with English abstract).

[48] 毛建仁, 蘇郁香, 陳三元, 程啟芬. 東南沿海中生代侵入巖及與火山巖的時(shí)空關(guān)系[J]. 資源調(diào)查與環(huán)境, 1989, 10(3): 44–59. Mao Jian-ren, Su Yu-xiang, Chen San-yuan, Cheng Qi-fen. Mesozoic intrustive rocks and their time-space relation with volcanic rocks in southeastern coast of China [J]. Resour Surv Environ, 1989, 10(3): 44–59 (in Chinese with English abstract).

[49] 徐曉春, 岳書倉. 粵東地區(qū)中生代巖漿作用的大地構(gòu)造背景及構(gòu)造-巖漿演化[J]. 合肥工業(yè)大學(xué)學(xué)報(bào)(自然科學(xué)版), 1996, 19(1): 127–134. Xu Xiao-chun, Yue Shu-cang. Tectonic background and evolution of Mesozoic magmatism, eastern Guangdong Province [J]. J Hefei Univ Technol, 1996, 19(1): 127–134 (in Chinese with English abstract).

[50] 陶奎元, 謝家瑩, 阮宏宏, 謝芳貴, 薛懷民. 中國東南沿海中生代火山作用基本特征[J]. 資源調(diào)查與環(huán)境, 1988, 9(4): 12–28. Tao Kui-Yuan, Xie Jia-ying, Ruan Hong-hong, Xie Fang-gui, Xue Huai-ming. Characteristics of the Mesozoic volcanism in the coastal margin of southeastern China [J]. Resour Surv Environ, 1988, 9(4): 12–28 (in Chinese with English abstract).

[51] 徐曉春, 岳書倉. 粵東中生代火山-侵入雜巖的地殼深熔成因——Pb-Nd-Sr多元同位素體系制約[J]. 地質(zhì)論評(píng), 1999, 45(增刊): 829–835. Xu Xiao-chun, Yue Shu-cnag. Continental crust anatexite: the genesis of Mesozoic granitic vocanic-intrusive complexes, estern Guangdong Province — Constuains on Pb-Nd-Sr multi-element isotopic systems [J]. Geol Rev, 1999, 45(suppl): 829–835 (in Chinese with English abstract).

[52] Zhou X M, Li W X. Origin of Late Mesozoic igneous rocks in Southeastern China: Implications for lithosphere subduction and underplating of mafic magmas [J]. Tectonophysics, 2000, 326(3/4): 269–287.

[53] Zhou X M, Sun T, Shen W Z, Shu L S, Niu Y L. Petrogenesis of Mesozoic granitoids and volcanic rocks in South China: A response to tectonic evolution [J]. Episodes, 2006, 29(1): 26–33.

[54] Li Z X, Li X H. Formation of the 1300-km-wide intracontinental orogen and postorogenic magmatic province in Mesozoic South China: A flat-slab subduction model [J]. Geology, 2007, 35(2): 179–182.

[55] Wong J, Sun M, Xing G F, Li X H, Zhao G C, Wong K, Yuan C, Xia X P, Li L M, Wu F Y. Geochemical and zircon U-Pb and Hf isotopic study of the Baijuhuajian metaluminous A-type granite: Extension at 125–100 Ma and its tectonic significance for South China [J]. Lithos, 2009, 112: 289–305.

[56] 毛景文, 謝桂青, 李曉峰, 張長青, 梅燕雄. 華南地區(qū)中生代大規(guī)模成礦作用與巖石圈多階段伸展[J]. 地學(xué)前緣, 2004, 11(1): 45–54.Mao Jing-wen, Xie Gui-qing, Li Xiao-feng, Zhang Chang- qing, Mei Yan-xiong. Mesozoic large scale mineralization and multiple lithospheric extension in South China [J]. Earth Science Frontiers, 2004, 11(1): 45–55 (in Chinese with English abstract).

[57] Gilder S A, Gill J, Coe R S, Zhao X X, Liu Z W, Wang G X, Yuan K R, Liu W L, Kuang G D, Wu H R. Isotopic and paleomagnetic constraints on the Mesozoic tectonic evolution of south China [J]. J Geophys Res, 1996, 101: 16137–16154.

[58] Wang Y J, Fan W M, Cawood P A, Li S Z. Sr-Nd-Pb isotopic constraints on multiple mantle domains for Mesozoic mafic rocks beneath the South China Block hinterland [J]. Lithos, 2008, 106: 297–308.

[59] Wang F Y, Ling M X, Ding X, Hu Y H, Zhou J B, Yang X Y, Liang H Y, Fan W M, Sun W D. Mesozoic large magmatic events and mineralization in SE China: Oblique subduction of the Pacific plate [J]. Int Geol Rev, 2011, 53: 704–726.

[60] Ling M X, Wang F Y, Ding X, Hu Y H, Zhou J B, Zartman R E, Yang X Y, Sun W D. Cretaceous ridge subduction along the Lower Yangtze River Belt, eastern China [J]. Econ Geol, 2009, 104: 303–321.

[61] Sun W D, Ding X, Hu Y H, Li X H. The golden transformation of the Cretaceous plate subduction in the west Pacific[J]. Earth Planet Sci Lett, 2007, 262: 533–542.

[62] Li X H, Li Z X, Ge W C, Zhou H W, Li W X, Liu Y, Wingate M T D. Neoproterozoic granitoids in South China: Crustal melting above a mantle plume at ca. 825 Ma? [J]. Precamb Res, 2003, 122: 45–83.

[63] 謝桂青. 中國東南部晚中生代以來的基性巖脈(體)的地質(zhì)地球化學(xué)特征及其地球動(dòng)力學(xué)意義初探——以江西省為例[D].貴陽: 中國科學(xué)院地球化學(xué)研究所, 2003: 1–128. Xie Gui-qing. Late Mesozoic mafic dikes (body) from southeastern China: Geological and geochemical characteristics and its geodynamics) —A Case of Jiangxi Province [D]. Guiyang: Institute of Geochemistry, Chinese Academy of Sciences, 2003: 1–128 (in Chinese with English abstract).

[64] Pearce J A. Sources and settings of granitic rocks [J]. Episodes, 1996, 19(4): 120–125.

[65] Batchelor R A, Bowden P. Petrogenetic interpretation of granitoid rock series using multicationic parameters [J]. Chem geol, 1985, 48(1): 43–55.

[66] 丘元禧, 丘津松, 李建超, 鐘宏平. 廣東蓮花山斷裂帶中、新生代多期復(fù)合變形變質(zhì)帶的基本特征及其形成機(jī)制的探討[J]. 中國地質(zhì)科學(xué)院地質(zhì)力學(xué)研究所所刊, 1991 (14): 93–106. Qiu Yuan-xi, Qiu Jin-song, Li Jian-chao, Zhong Hong-ping. Deformational and metamorphic features of Lianhuashan fault zone during Meso-Cenozoic time and mechanism of their formation [J]. Bull Inst of Geomechan CAGS, 1991 (14): 93–106 (in Chinese with English abstract).

Zircon U-Pb geochronology and Lu-Hf isotopic composition of quartz porphyry in the Changpu Sn polymetallic deposit, Guangdong Province, SE China and their geological significance

QIU Zeng-wang1,2, WANG He1*, YAN Qing-he1,2, LI Sha-sha1,2, WANG Li-ming3, BU An4, MU Sheng-lu1,2, LI Pei1,2and WEI Xiao-peng1,2

1. Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemisty, Chinese Academy of Sciences, Guangzhou 510640, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China; 3. Geology Bureau for Nonferrous Metals of Guangdong Province, Guangzhou 510060, China; 4. Geology Bureau for Nonferrous Metals of Guangdong Province 931 Battalion, Shantou 515041, China

The Changpu Sn polymetallic deposit is located in the Lianhuashan Fault Belt, eastern Guangdong Province. The deposit is a medium-sized hydrothermal vein-type Sn-Pb-Zn deposit, and genetically related to quartz porphyry. In this paper, zircon U-Pb geochronology and Lu-Hf isotopic composition of quartz porphyry have been obtained for the first time. Zircon LA-ICP-MS dating of quartz porphyry yields a concordant age of (145.0±0.9) Ma, indicating the quartz porphyry was formed in the Early Cretaceous. The Hf isotopic composition of the quartz porphyry shows that theHf() values vary from –7.95 to –2.74 withDM2ages of 1371 Ma to 1704 Ma, suggesting that the Changpu quartz porphyry probably originated from partial melting of the Mesoproterozoic ancient crustal rocks with a minor input of some mantle materials. Based on the analytical results and regional tectonic evolution, the quartz porphyry of the Changpu deposit was suggested to have been formed in a post-collision extensional tectonic setting that was triggered by the subduction of the paleo-Pacific plate.

zircon U-Pb dating; Hf isotope; quartz porphyry; Changpu Sn polymetallic deposit; Guangdong Province

P597.3; P588.121

A

0379-1726(2016)04-0374-13

2015-12-10;

2016-02-01;

2016-02-20

中國地質(zhì)調(diào)查局整裝勘查關(guān)鍵基礎(chǔ)地質(zhì)研究項(xiàng)目(12120114015901)

丘增旺(1989–), 男, 博士研究生, 礦物學(xué)、巖石學(xué)、礦床學(xué)專業(yè)。E-mail: qzwdeng@163.com

WANG He, E-mail: wanghe @gig.ac.cn, Tel: +86-20-85291422