蔡佳 劉福來 劉平華 王舫 施建榮
CAI Jia,LIU FuLai,LIU PingHua,WANG Fang and SHI JianRong
中國(guó)地質(zhì)科學(xué)院地質(zhì)研究所,北京 100037
Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China
2015-03-01 收稿,2015-05-26 改回.
內(nèi)蒙孔茲巖帶位于華北克拉通西北緣,是一條由西部陸塊內(nèi)北部的陰山陸塊和南部的鄂爾多斯陸塊碰撞形成的古元古代碰撞構(gòu)造帶,該孔茲巖帶出露大面積孔茲巖系巖石(Zhao et al.,1999,2003,2005,2012;Zhai et al.,2000),分布在西段賀蘭山-千里山、中段烏拉山-大青山和東段集寧地區(qū)。近年來,研究者們先后對(duì)上述孔茲巖系巖石的成因礦物學(xué)、變質(zhì)演化、地球化學(xué)、同位素年代學(xué)和構(gòu)造演化等方面進(jìn)行了深入研究,并取得一系列重要進(jìn)展(金巍,1989;金巍等,1991;盧良兆等,1992,1996;Liu et al.,1993,1998,2013,2014;Lu and Jin,1993;李樹勛等,1994;劉喜山,1994,1996;于海峰,1994;金巍和李樹勛,1996;劉福來等,2002;Santosh et al.,2006,2007a,b,2009a,b;Wan et al.,2006,2009,2013a,b;Xia et al.,2006a,b,2008;Dong et al.,2007,2013,2014;Yin et al.,2009,2011,2014;周喜文等,2010;Yin,2010;Jiao and Guo,2011;Li et al.,2011;Jiao et al.,2013a,b;Dan et al.,2012;Guo et al.,2012;Ma et al.,2012;劉平華等,2013;蔡佳等,2013a,b,2014)。其中,很多研究者對(duì)孔茲巖帶出露的孔茲巖系巖石進(jìn)行了變質(zhì)作用研究,普遍得到了近等溫減壓型的順時(shí)針P-T 軌跡(盧良兆等,1992;Liu et al.,1993;Lu and Jin,1993;Yin,2010;周喜文等,2010;Wang et al.,2011;Jiao et al.,2013a;蔡佳等,2013a,2014;Cai et al.,2014;Yin et al.,2014)。此外,大量的鋯石同位素年代學(xué)研究表明孔茲巖帶的孔茲巖系巖石記錄了1810 ~1950Ma 的變質(zhì)年齡(Wan et al.,2006,2009,2013a;Xia et al.,2006a,b;Dong et al.,2007,2013;Yin et al.,2009,2011;周喜文和耿元生,2009;Jiao et al.,2013b),有研究者認(rèn)為~1950Ma 可能代表了北部的陰山陸塊和南部鄂爾多斯陸塊碰撞拼合的時(shí)代(Yin et al.,2009,2011;趙國(guó)春,2009;周喜文和耿元生,2009;Zhao et al.,2010;Dong et al.,2013),1920 ~1890Ma 則可能是碰撞后折返的時(shí)代(Yin et al.,2009;Jiao et al.,2013b)。然而,Wan et al. (2013a)獲得了烏拉山-大青山變基性巖1920 ~1970Ma 的巖漿年齡,反映了古元古代的陸內(nèi)伸展事件,而并非陸-陸碰撞拼合的時(shí)代。最近,Dong et al. (2014)通過SHRIMP 鋯石U-Pb 年代學(xué)研究,報(bào)道了大青山孔茲巖系巖石存在晚太古代(2.45~2.40Ga)和古元古代(1.95 ~1.90Ga)兩期變質(zhì)事件,類似地,Liu et al. (2014)也報(bào)道了烏拉山-大青山變基性巖的晚太古代(~2.45Ga)和古元古代(1.95 ~1.85Ga)兩期變質(zhì)事件,反映烏拉山-大青山高級(jí)變質(zhì)巖石經(jīng)歷了十分復(fù)雜的構(gòu)造-熱演化歷史。然而,由于晚太古代變質(zhì)事件可能普遍遭受了古元古代變質(zhì)事件的改造,在巖相學(xué)和變質(zhì)作用等其它方面仍難以很好地區(qū)分二者,這也為正確認(rèn)識(shí)晚太古代變質(zhì)事件的變質(zhì)演化歷史、成因機(jī)制以及構(gòu)造背景帶來了很大的挑戰(zhàn)。
不同于孔茲巖帶中段烏拉山-大青山地區(qū)的晚太古代變質(zhì)事件,目前,有關(guān)該區(qū)孔茲巖系巖石和變基性巖石的古元古代變質(zhì)事件的相關(guān)研究已取得了眾多研究進(jìn)展。本文在前期變質(zhì)作用研究的基礎(chǔ)上,選取了孔茲巖帶烏拉山-大青山地區(qū)典型的孔茲巖系巖石,包括堇青石榴黑云二長(zhǎng)片麻巖、夕線堇青石榴黑云二長(zhǎng)片麻巖、紫蘇石榴黑云片麻巖和石榴長(zhǎng)英質(zhì)粒狀巖石,其中(夕線)堇青石榴黑云二長(zhǎng)片麻巖保留多種退變質(zhì)反應(yīng)結(jié)構(gòu),Cai et al. (2014)對(duì)該類樣品進(jìn)行了詳細(xì)的變質(zhì)作用研究,劃分出進(jìn)變質(zhì)、峰期變質(zhì)、峰后近等溫減壓以及晚期降溫冷卻四個(gè)變質(zhì)階段的礦物共生組合,并利用相平衡模擬的方法計(jì)算出不同巖石樣品的P-T 視剖面圖,建立了烏拉山-大青山地區(qū)孔茲巖系巖石近等溫減壓型的順時(shí)針P-T 演化軌跡。因此,本文在此研究的基礎(chǔ)上,通過詳細(xì)的野外地質(zhì)觀察和室內(nèi)巖相學(xué)觀察,利用LA-ICPMS 鋯石U-Pb 年代學(xué)研究分別獲得了該區(qū)孔茲巖系巖石的原巖形成時(shí)代和變質(zhì)時(shí)代,并結(jié)合前人的研究結(jié)果,將其變質(zhì)時(shí)代劃分為~1950Ma 和~1860Ma 兩個(gè)階段,分別對(duì)應(yīng)了陸-陸碰撞初始階段和折返抬升的時(shí)代,為進(jìn)一步揭示古元古代華北克拉通西部的陰山陸塊和鄂爾多斯陸塊之間的俯沖-碰撞并折返至地表的動(dòng)力學(xué)過程提供科學(xué)依據(jù)。
內(nèi)蒙古孔茲巖帶位于華北克拉通西北緣,是一條古元古代碰撞構(gòu)造帶,由西向東沿千里山-賀蘭山、烏拉山-大青山和集寧-卓資-豐鎮(zhèn)一帶展布,北鄰陰山陸塊,南側(cè)與鄂爾多斯陸塊相接(圖1a,b),東側(cè)緊鄰中部造山帶。前人研究(Zhao et al.,1999,2002,2005;Zhai et al.,2000)認(rèn)為孔茲巖帶是由北部的陰山陸塊和南部的鄂爾多斯陸塊于 ~1950Ma 碰撞拼合而成,而中部造山帶是由西部陸塊與東部陸塊在~1850Ma碰撞形成。本文研究區(qū)位于孔茲巖帶中段的烏拉山-大青山地區(qū),是典型的孔茲巖系出露區(qū)(圖1a,b)。
圖1 孔茲巖帶在華北克拉通的分布和構(gòu)造位置圖(a,b,據(jù)Zhao et al.,2005)和烏拉山-大青山地區(qū)的地質(zhì)簡(jiǎn)圖及采樣位置(c,據(jù)徐仲元等,2007)圖中所示的大青山地區(qū)變泥質(zhì)巖石的鋯石年齡數(shù)據(jù)分別來自Wan et al. (2009)和Dong et al. (2013,2014)Fig.1 Distribution of the Khondalite Belt in the North China Craton (a,b,after Zhao et al.,2005)and geological map of the Wulashan-Daqingshan area (c,after Xu et al.,2007)Zircon age data of the metapelitic rocks in the Daqingshan area are from Wan et al. (2009)and Dong et al. (2013,2014)
烏拉山-大青山地區(qū)出露的早前寒武紀(jì)變質(zhì)巖石的類型十分復(fù)雜,包括太古代興和巖群麻粒巖系、古元古代烏拉山巖群和美岱召巖群的變質(zhì)表殼巖系(孔茲巖系)、太古代深變質(zhì)巖漿巖、古元古代巖漿巖以及少量古元古代(石榴)基性麻粒巖和斜長(zhǎng)角閃巖(盧良兆等,1992,1996;徐仲元等,2007)。其中,古元古代烏拉山巖群孔茲巖系主要分布于包頭以北的哈德門溝、忽雞溝、大南溝、五當(dāng)召和雞燈灣等地,包括兩個(gè)巖石單元,下部主要是黑云角閃質(zhì)片麻巖,巖石類型包括含石英輝石斜長(zhǎng)角閃巖、含石英鉀長(zhǎng)/二長(zhǎng)角閃巖、斜長(zhǎng)角閃巖、角閃斜長(zhǎng)片麻巖、黑云角閃斜長(zhǎng)片麻巖、黑云角閃二長(zhǎng)片麻巖、黑云鉀長(zhǎng)/二長(zhǎng)片麻巖夾輝石磁鐵石英巖等(李樹勛等,1994);而上部巖石單元總體與孔茲巖系相當(dāng),主要為石榴黑云二長(zhǎng)/斜長(zhǎng)片麻巖、夕線石榴堇青黑云二長(zhǎng)/斜長(zhǎng)片麻巖、(石墨)大理巖、長(zhǎng)英質(zhì)粒狀巖石、黑云變粒巖等,部分地區(qū)見基性麻粒巖透鏡體出露(劉平華等,2013;Liu et al.,2014)。在局部地區(qū)出露的石榴石花崗巖與高級(jí)變質(zhì)表殼巖系密切伴生,可能與區(qū)內(nèi)麻粒巖相變質(zhì)演化所伴隨的部分熔融作用有關(guān)(盧良兆等,1996)。
采樣點(diǎn)位于孔茲巖帶烏拉山-大青山地區(qū)的雞燈灣、忽雞溝、石拐區(qū)以北的五當(dāng)召以及哈德門溝一帶,出露變質(zhì)程度較高且具有多種變質(zhì)反應(yīng)結(jié)構(gòu)的孔茲巖系巖石(圖1c)。典型樣品包括堇青石榴黑云二長(zhǎng)片麻巖(BH27-1)、夕線堇青石榴黑云二長(zhǎng)片麻巖(BH27-2 和BT20-1)、紫蘇石榴黑云片麻巖(BH27-3 和BT38-1)和石榴長(zhǎng)英質(zhì)粒狀巖石(BH28-1),其野外產(chǎn)狀和室內(nèi)巖相學(xué)特征描述如下(圖2、圖3)。
圖2 烏拉山-大青山地區(qū)孔茲巖系巖石野外露頭照片(a)堇青石榴黑云二長(zhǎng)片麻巖(BH27-1)與夕線堇青石榴黑云二長(zhǎng)片麻巖(BH27-2)共同產(chǎn)出;(b)堇青石榴黑云二長(zhǎng)片麻巖(BH27-1)中石榴石的邊部形成“黑眼圈”結(jié)構(gòu);(c)夕線堇青石榴黑云二長(zhǎng)片麻巖的礦物組合(BH27-2)夕線石+石榴石+堇青石+黑云母+ 長(zhǎng)石+ 石英;(d)紫蘇石榴黑云斜長(zhǎng)片麻巖(BH27-3)的礦物組合紫蘇輝石+ 石榴石+ 黑云母+ 斜長(zhǎng)石;(e)夕線堇青石榴黑云二長(zhǎng)片麻巖(BT20-1)呈似層狀產(chǎn)出;(f)夕線堇青石榴黑云二長(zhǎng)片麻巖(BT20-1)的礦物組合夕線石+石榴石+堇青石+黑云母+長(zhǎng)石+石英;(g)紫蘇石榴黑云二長(zhǎng)片麻巖(BT38-1)中可見多處長(zhǎng)英質(zhì)淺色條帶和長(zhǎng)石斑晶;(h)石榴長(zhǎng)英質(zhì)粒狀巖石(BH28-1)的礦物組合石榴石+黑云母+石英+斜長(zhǎng)石Fig.2 Outcrops of the khondalite rocks in the Wulashan-Daqingshan area(a) cordierite-garnet-biotite gneiss (BH27-1) associated with sillimanite-cordierite-garnet gneiss (BH27-2);(b)cordierite that forms a black ring around garnet(‘black-eye-socket’structure)in cordierite-garnet-biotite gneiss (BH27-1 ); (c ) sillimanitecordierite-garnet gneiss (BH27-2) with mineral assemblage of sillimanite+ garnet + cordierite + biotite + feldspar + quartz;(d)hypersthene-garnet-biotite gneiss (BH27-3)with mineral assemblage of hypersthene + garnet + biotite + plagioclase;(e)sillimanitecordierite-garnet gneiss (BT20-1 ) occurred in layers; (f)sillimanite-cordierite-garnet gneiss (BT20-1 ) with mineral assemblage of sillimanite + garnet + cordierite + biotite + feldspar +quartz;(g)quartzofeldspathic layers and porphyroblastic feldspar occur in the hypersthene-garnet-biotite gneiss (BT38-1);(h)garret-bearing quartzofeldspathic rock (BH28-1 ) with mineral assemblage of garnet+biotite+quartz+plagioclase
堇青石榴黑云二長(zhǎng)片麻巖(BH27-1)樣品采自土默特右旗公山灣鄉(xiāng)雞燈灣村東約1.1km 公路旁(圖2a,b),該區(qū)出露的巖石類型還包括夕線堇青石榴黑云二長(zhǎng)片麻巖(BH27-2)、紫蘇石榴黑云斜長(zhǎng)片麻巖(BH27-3)和斜長(zhǎng)角閃巖等,出露寬度約100m,其中堇青石榴黑云二長(zhǎng)片麻巖和夕線堇青石榴黑云二長(zhǎng)片麻巖呈似層狀產(chǎn)出。石榴石邊部圍繞不透明暗色礦物形成“黑眼圈”結(jié)構(gòu)。該樣品的主要組成礦物有石榴石、長(zhǎng)石、石英、堇青石、黑云母,并含少量夕線石等,副礦物為鋯石、磁鐵礦和鈦鐵礦等。其中石榴石變斑晶呈渾圓狀,粒徑變化較大(0.1 ~1.5cm),含量2% ~10%。部分石榴石核-幔部可包裹大量細(xì)長(zhǎng)針狀夕線石、細(xì)粒石英、長(zhǎng)石和黑云母等礦物(圖3a)。堇青石圍繞在石榴石邊部形成退變反應(yīng)邊結(jié)構(gòu),其內(nèi)包裹黑云母、石英、Fe-Ti 氧化物和鋯石等(圖3a)。
夕線堇青石榴黑云二長(zhǎng)片麻巖(BH27-2)樣品和堇青石榴黑云二長(zhǎng)片麻巖(BH27-1)取自同一露頭(圖2c),該樣品的主要組成礦物為石榴石、夕線石、堇青石、黑云母、長(zhǎng)石、石英等,副礦物為鋯石、磁鐵礦和鈦鐵礦等(圖3b)。石榴石邊部可被大量粗粒黑云母和夕線石圍繞。堇青石多分布在基質(zhì)中,與黑云母和長(zhǎng)英質(zhì)礦物共生,而不與石榴石直接接觸,局部呈拉長(zhǎng)狀沿片麻理方向分布,其內(nèi)可包裹細(xì)粒黑云母、石英、殘留狀的夕線石、尖晶石和Fe-Ti 氧化物等,少數(shù)堇青石圍繞在石榴石邊部形成退變反應(yīng)邊結(jié)構(gòu)。
夕線堇青石榴黑云二長(zhǎng)片麻巖(BT20-1)樣品來自包頭市九原區(qū)烏蘭計(jì)鎮(zhèn)柏樹溝村西北約250m 的山坡上,主要出露一套夕線堇青石榴黑云二長(zhǎng)片麻巖和石榴黑云二長(zhǎng)片麻巖,二者呈互層狀產(chǎn)出,局部可見含石榴石的長(zhǎng)英質(zhì)淺色體聚集,其中長(zhǎng)石呈眼球狀沿片麻理分布(圖2e,f)。該樣品的主要組成礦物有石榴石、長(zhǎng)石、石英、堇青石、黑云母和夕線石等,并含少量鋯石、磁鐵礦和鈦鐵礦。石榴石變斑晶呈渾圓狀或拉長(zhǎng)狀,粒徑變化為0.2 ~0.8cm。石榴石可包裹細(xì)粒石英、長(zhǎng)石、黑云母和夕線石等礦物。石榴石邊部可被大量粗粒黑云母和夕線石圍繞(圖3c),部分石榴石邊部形成含堇青石或鱗片狀黑云母+斜長(zhǎng)石的退變邊結(jié)構(gòu)?;|(zhì)中的堇青石常與黑云母和長(zhǎng)英質(zhì)礦物共生。
紫蘇石榴黑云斜長(zhǎng)片麻巖(BH27-3)樣品和BH27-1、BH27-2 樣品取自同一露頭(圖2d),兩類巖石呈漸變過渡關(guān)系。該樣品的主要組成礦物為石榴石、紫蘇輝石(粒徑約0.5 ~2.5mm)、斜長(zhǎng)石、黑云母等,并含少量鉀長(zhǎng)石和石英等。其中石榴石變斑晶可包裹紫蘇輝石、黑云母、石英和長(zhǎng)石等(圖3d)。局部石榴石分解形成紫蘇輝石+斜長(zhǎng)石的后成合晶,石英和斜長(zhǎng)石被鉀長(zhǎng)石所分隔。
圖3 烏拉山-大青山地區(qū)孔茲巖系巖石代表性礦物組合及顯微結(jié)構(gòu)特征(單偏光照片)(a)石榴石變斑晶包裹細(xì)粒毛發(fā)狀夕線石和石英等,其邊部圍繞堇青石退變邊;(b)基質(zhì)中的石榴石、夕線石、黑云母、石英、長(zhǎng)石、鋯石和磁鐵礦共同產(chǎn)出;(c)石榴石變斑晶邊部退變?yōu)檩狼嗍?蝕變),并圍繞粗粒夕線石和黑云母等;(d)石榴石變斑晶內(nèi)包裹紫蘇輝石、黑云母和斜長(zhǎng)石等,邊部圍繞粗粒黑云母;(e)基質(zhì)中的石榴石、紫蘇輝石、黑云母、斜長(zhǎng)石、鉀長(zhǎng)石和石英等;(f)基質(zhì)中的渾圓狀石榴石、石英、斜長(zhǎng)石、黑云母和金紅石等,石榴石內(nèi)包裹石英和斜長(zhǎng)石Fig.3 Representative photomicrographs showing mineral assemblages and microtextures of the khondalite rocks in the Wulashan-Daqingshan area (plane-polarized light photos)(a)fibrolitic sillimanite and quartz included in porphyroblastic garnet,and the garnet rimmed by a corona of cordierite;(b)garnet porphyroblast,coarse-grained sillimanite,biotite,quartz and feldspar in the matrix in contact with zircon and magnetite;(c)a garnet porphyroblast mantled by pinitized cordierite,coarse-grained sillimanite,and biotite;(d)hypersthene,biotite and minute plagioclase preserved within a garnet porphyroblast which is surrounded by coarse-grained biotite;(e)matrix garnet,hypersthene,biotite,plagioclase,K-feldspar and quartz;(f)rounded garnet,quartz,plagioclase,biotite and rutile in the matrix,and porphyroblastic garnet contains quartz and plagioclase
紫蘇石榴黑云二長(zhǎng)片麻巖(BT38-1)樣品取自包頭市石拐區(qū)烏蘭此老村東側(cè)石拐-五當(dāng)召線公路旁,巖石呈似層狀產(chǎn)出。巖石局部含有淺色長(zhǎng)英質(zhì)條帶,并可見斜長(zhǎng)石的巨晶(圖2g)。該樣品主要組成礦物為石榴石、紫蘇輝石、斜長(zhǎng)石、鉀長(zhǎng)石、石英和黑云母等(圖3e),副礦物有磁鐵礦、鈦鐵礦和鋯石等。石榴石變斑晶可包裹黑云母、長(zhǎng)石、紫蘇輝石和尖晶石-磁鐵礦-鈦鐵礦出溶體。紫蘇輝石呈不規(guī)則粒狀,粒徑約0.05 ~2.5mm,其內(nèi)可定向出溶細(xì)長(zhǎng)針狀鈦鐵礦。
石榴長(zhǎng)英質(zhì)粒狀巖石(BH28-1)樣品取自固陽縣忽雞溝鄉(xiāng)大南溝村南偏東約750m 山坡上,該巖石與石榴堇青黑云斜長(zhǎng)片麻巖、尖晶黑云石榴鉀長(zhǎng)片麻巖共同產(chǎn)出。石榴長(zhǎng)英質(zhì)粒狀巖石的主要組成礦物有石英、長(zhǎng)石、石榴石和黑云母等(圖2h),副礦物有褐紅色金紅石、磁鐵礦和鋯石等。石榴石多呈渾圓粒狀,粒徑0.50 ~2.00mm,其核-幔部包裹細(xì)粒石英、長(zhǎng)石和黑云母等(圖3f)。
圖4 堇青石榴黑云二長(zhǎng)片麻巖(BH27-1)鋯石陰極發(fā)光圖像和LA-ICP-MS U-Pb 定年結(jié)果(a)鋯石具有核-邊結(jié)構(gòu),繼承性核部具有相對(duì)強(qiáng)發(fā)光效應(yīng)(灰白-灰色),變質(zhì)邊具有相對(duì)均勻的中等發(fā)光效應(yīng)(灰黑色);(b、c)鋯石具中等-弱發(fā)光效應(yīng)(灰-灰黑色),具巖漿結(jié)晶環(huán)帶;(d)鋯石具有核-邊結(jié)構(gòu);(e、f)鋯石具有相對(duì)均勻的弱發(fā)光效應(yīng)(灰黑色-黑色);(g)鋯石具有核-邊結(jié)構(gòu),邊部具有相對(duì)均勻的弱發(fā)光效應(yīng)(黑色);(h)鋯石具有核-邊結(jié)構(gòu),邊部具有相對(duì)均勻的中等發(fā)光效應(yīng)(灰色)Fig.4 Cathodoluminescent (CL)images and LA-ICP-MS U-Pb ages of zircons from the Crd-Grt-Bt gneiss (BH27-1)(a)the zircon grain showing high-luminescent (greyish white-grey)core,middle-luminescent (greyish black)rim relationship;(b,c)the zircon grains showing middle-low-luminescent (grey-greyish black)magmatic zoning;(d)the zircon grain showing greyish black-luminescent core and rim;(e,f)the zircon grains showing homogeneous low-luminescence (greyish black-black);(g)the zircon grain showing middle-luminescent core and low-luminescent (black)rim;(h)the zircon grain showing low-luminescent core and middle-luminescent (grey)rim
巖石樣品的破碎與鋯石分選在河北省區(qū)域地質(zhì)調(diào)查所礦物分選實(shí)驗(yàn)室完成。首先,將樣品(約5kg)進(jìn)行破碎至適當(dāng)粒級(jí),經(jīng)清洗、烘干和篩選后,采用磁選和重液分選出不同粒級(jí)的鋯石晶體,然后在雙目鏡下挑選出顆粒相對(duì)完整的鋯石晶體約200 粒,制成符合陰極發(fā)光測(cè)試和LA-ICP-MS U-Pb定年的標(biāo)準(zhǔn)鋯石靶。鋯石的LA-ICP-MS U-Pb 定年測(cè)試在天津地質(zhì)礦產(chǎn)研究所同位素實(shí)驗(yàn)室Neptune 型LA-ICP-MS 上進(jìn)行,該實(shí)驗(yàn)測(cè)試條件詳見耿建珍等(2012)的論述。本文所有礦物代號(hào)均采用Whitney and Evans (2010)的資料。由于LA-ICP-MS 定年手段對(duì)鋯石的剝蝕深度較大,對(duì)于具有環(huán)帶或結(jié)構(gòu)不均一的鋯石,容易獲得混合年齡。因此對(duì)于具核邊結(jié)構(gòu)的鋯石,盡量選擇變質(zhì)邊較寬且結(jié)構(gòu)均一的位置進(jìn)行測(cè)試;對(duì)于結(jié)構(gòu)均勻的變質(zhì)鋯石,避免選擇靠中心的位置進(jìn)行測(cè)試,以免灼燒到小顆粒的繼承性核部鋯石;對(duì)于具有巖漿結(jié)晶環(huán)帶的繼承性碎屑鋯石或是具核邊結(jié)構(gòu)的繼承性鋯石核部,也盡量選擇核部顆粒較大且?guī)r漿結(jié)晶環(huán)帶清晰的位置。此外,對(duì)不同樣品盡量多選擇測(cè)試點(diǎn),使獲得的年齡數(shù)據(jù)更具統(tǒng)計(jì)意義,以降低個(gè)別的混合年齡對(duì)最終年齡結(jié)果的影響。
堇青石榴黑云二長(zhǎng)片麻巖(BH27-1)中的鋯石呈暗紫紅色,不透明-半透明,以不規(guī)則粒狀或短柱狀為主,少數(shù)為渾圓狀,長(zhǎng)寬比多為1 ∶1 ~2 ∶1。鋯石顆粒較小,為40 ~150μm。根據(jù)鋯石陰極發(fā)光(CL)圖像與形態(tài)特征可劃分出兩種類型:其一具有核-邊結(jié)構(gòu),即強(qiáng)-弱發(fā)光效應(yīng)(灰白-灰黑色)的繼承性核和相對(duì)弱發(fā)光(灰黑色-黑色)效應(yīng)的變質(zhì)增生邊(圖4a-d,g,h),核部與邊部之間多呈漸變過渡,其中繼承性的核多發(fā)育巖漿結(jié)晶環(huán)帶,部分繼承性的核由于受到麻粒巖相變質(zhì)作用的影響導(dǎo)致早期韻律環(huán)帶被強(qiáng)烈改造而產(chǎn)生較模糊的巖漿結(jié)晶環(huán)帶,變質(zhì)增生邊結(jié)構(gòu)較均勻,無分帶特征,邊部寬窄不一,多在2 ~30μm 之間;其二多呈渾圓狀,具有相對(duì)均勻的中等-弱發(fā)光效應(yīng)(多呈灰-黑色),可發(fā)育冷杉葉結(jié)構(gòu),內(nèi)部無分帶(圖4e,f),具變質(zhì)鋯石的特征。
夕線堇青石榴黑云二長(zhǎng)片麻巖(BH27-2)與堇青石榴黑云二長(zhǎng)片麻巖(BH27-1)中的鋯石特征類似,粒徑變化于80~200μm,以渾圓狀或不規(guī)則粒狀為主,少數(shù)為短柱狀,長(zhǎng)寬比多為1∶1 ~2∶1。CL 圖像同樣顯示兩種類型的鋯石:第一種具典型的核-邊結(jié)構(gòu)(圖5a,b),繼承性的核部呈不規(guī)則粒狀,多發(fā)育巖漿結(jié)晶環(huán)帶,具強(qiáng)-弱發(fā)光效應(yīng)(灰白-灰黑色),而變質(zhì)增生邊的結(jié)構(gòu)較均勻,多呈中等-弱發(fā)光效應(yīng)(灰色-灰黑色),寬度為5 ~60μm,繼承性核部與邊部之間的界限較清晰;第二種類型多呈渾圓狀,內(nèi)部結(jié)構(gòu)均勻,少數(shù)發(fā)育冷杉葉結(jié)構(gòu),具均勻的弱發(fā)光效應(yīng)(灰黑色-黑色),具有變質(zhì)鋯石的特征(圖5c-h)。
夕線堇青石榴黑云二長(zhǎng)片麻巖(BT20-1)中的鋯石以渾圓狀為主,少數(shù)呈短柱狀,粒徑為50 ~300μm。CL 圖像顯示兩種類型的鋯石:其一具核-邊結(jié)構(gòu)(圖6a-c,e,h),其中繼承性核部呈不規(guī)則粒狀或柱狀,具中等-弱發(fā)光效應(yīng),可顯示清晰的巖漿結(jié)晶環(huán)帶,而其周圍的變質(zhì)增生邊呈均勻的中等-弱發(fā)光效應(yīng)(灰色-灰黑色),邊部寬度不一,在5 ~80μm之間;其二為具有均勻的弱發(fā)光效應(yīng)的變質(zhì)鋯石,內(nèi)部無分帶結(jié)構(gòu)(圖6d,f,g)。
圖5 夕線堇青石榴黑云二長(zhǎng)片麻巖(BH27-2)鋯石陰極發(fā)光圖像和LA-ICP-MS U-Pb 定年結(jié)果(a)鋯石具核-邊結(jié)構(gòu),繼承性核部和邊部均具相對(duì)弱發(fā)光效應(yīng)(灰-灰黑色),核部顯示巖漿結(jié)晶環(huán)帶;(b)鋯石具核-邊結(jié)構(gòu),繼承性核部具中等-弱發(fā)光效應(yīng)(灰黑色),邊部具中等發(fā)光效應(yīng)(灰色);(c-h)鋯石多呈渾圓粒狀,具有相對(duì)均勻的弱發(fā)光效應(yīng)(灰黑色-黑色)Fig.5 CL images and LA-ICP-MS U-Pb ages of zircons from the Sil-Crd-Grt gneiss (BH27-2)(a)the zircon grain showing low-luminescent (grey-greyish black)magmatic zoning core and rim;(b)the zircon grain showing middle-lowluminescent core (greyish black)and middle-luminescent rim (grey);(c-h)the rounded zircon grains showing homogeneous low-luminescence(greyish black-black)
圖6 夕線堇青石榴黑云二長(zhǎng)片麻巖(BT20-1)鋯石陰極發(fā)光圖像和LA-ICP-MS U-Pb 定年結(jié)果(a、b)鋯石具有核-邊結(jié)構(gòu),繼承性核顯示巖漿結(jié)晶環(huán)帶,具中等發(fā)光效應(yīng)(灰色),邊部具均勻的中等-弱發(fā)光效應(yīng)(灰-灰黑色);(c)鋯石具核-邊結(jié)構(gòu),邊部顯示均勻的中等發(fā)光效應(yīng)(灰黑色);(d)鋯石具有均勻的弱發(fā)光效應(yīng);(e)鋯石具有核-邊結(jié)構(gòu),邊部具有相對(duì)均勻的弱發(fā)光效應(yīng)(灰黑色-黑色);(f、g)鋯石具有相對(duì)均勻的弱發(fā)光效應(yīng)(灰黑色-黑色);(h)鋯石具有核-邊結(jié)構(gòu),邊部具有相對(duì)均勻的弱發(fā)光效應(yīng)(灰黑色)Fig.6 CL images and LA-ICP-MS U-Pb ages of zircons from the Sil-Crd-Grt gneiss (BT20-1)(a,b)the zircon grains showing middle-luminescent (grey)magmatic zoning core and middle-low-luminescent (grey-greyish black)rim relationship;(c)the zircon grain showing low-luminescent core and homogeneous middle-luminescent (greyish black)rim;(d)the zircon grain showing homogeneous low-luminescence;(e)the zircon grain showing low-luminescent (greyish black-black)core and rim;(f,g)the zircon grains showing homogeneous low-luminescence (greyish black-black);(h)the zircon grain showing low-luminescent (greyish black)rim
紫蘇石榴黑云斜長(zhǎng)片麻巖(BH27-3)中的鋯石呈渾圓狀、不規(guī)則粒狀或短柱狀,長(zhǎng)寬比為1∶1 ~3∶1。鋯石顆粒多較小,粒徑約60 ~130μm。CL 圖像顯示三種類型的鋯石:其一具有核-邊結(jié)構(gòu),即中等-弱發(fā)光效應(yīng)(灰色-黑色)的繼承性核和相對(duì)均勻的弱發(fā)光(灰黑色-黑色)效應(yīng)的變質(zhì)增生邊,繼承性核呈不規(guī)則狀(圖7a,f,g),內(nèi)部可發(fā)育巖漿結(jié)晶環(huán)帶或結(jié)構(gòu)均勻,核部與邊部之間界限較清晰,變質(zhì)增生邊常具有均勻的灰黑-黑色的弱發(fā)光效應(yīng),無分帶特征,變質(zhì)邊寬度在2 ~30μm 之間;其二呈長(zhǎng)柱狀,內(nèi)部發(fā)育典型的巖漿結(jié)晶環(huán)帶,具有中等-弱的發(fā)光效應(yīng)(圖7b);其三多呈渾圓狀,少數(shù)呈半自形-自形晶,具有相對(duì)均勻的中等-弱發(fā)光效應(yīng)(灰-灰黑色),內(nèi)部無分帶特征,可發(fā)育冷杉葉結(jié)構(gòu),具有變質(zhì)鋯石的特征(圖7c-e,h)。
紫蘇石榴黑云二長(zhǎng)片麻巖(BT38-1)中的鋯石主要呈短柱狀、渾圓狀或不規(guī)則狀,粒徑變化于80 ~200μm 之間。CL圖像顯示兩種鋯石:其一具核-邊結(jié)構(gòu)(圖8a-f,h-j),多呈柱狀,少數(shù)呈渾圓狀,其中繼承性核部具有中等-弱發(fā)光效應(yīng)(灰黑-黑色),其內(nèi)部結(jié)構(gòu)均勻,少數(shù)具有巖漿結(jié)晶環(huán)帶,而變質(zhì)增生邊多具均勻的中等-弱發(fā)光效應(yīng)(灰色-灰黑色),內(nèi)部無分帶現(xiàn)象,邊部寬度變化較大(20 ~150μm);其二具有均勻的中等發(fā)光效應(yīng)(灰白-灰黑色),多呈渾圓狀,發(fā)育冷杉葉結(jié)構(gòu)(圖8g,k,l)。
圖7 紫蘇石榴黑云斜長(zhǎng)片麻巖(BH27-3)鋯石陰極發(fā)光圖像和LA-ICP-MS U-Pb 定年結(jié)果(a)鋯石具有核-邊結(jié)構(gòu),繼承性核部具中等-弱發(fā)光效應(yīng)(灰-灰黑色)并具巖漿結(jié)晶環(huán)帶,變質(zhì)邊具有相對(duì)均勻的弱發(fā)光效應(yīng)(灰黑-黑色);(b)鋯石呈柱狀,有典型的巖漿結(jié)晶環(huán)帶,具中等-弱發(fā)光效應(yīng)(灰-灰黑色);(c-e)鋯石具有相對(duì)均勻的中等-弱發(fā)光效應(yīng)(灰色-黑色);(f、g)鋯石具有核-邊結(jié)構(gòu),繼承核較小且具中等-弱發(fā)光效應(yīng),邊部具有相對(duì)均勻的弱發(fā)光效應(yīng)(灰黑-黑色);(h)鋯石具有相對(duì)均勻的弱發(fā)光效應(yīng)(灰黑色-黑色)Fig.7 CL images and LA-ICP-MS U-Pb ages of zircons from the Hyp-Grt-Bt gneiss (BH27-3)(a)the zircon grain showing middle-low-luminescent (grey-greyish black)magmatic zoning core,low-luminescent (greyish black-black)rim relationship;(b)the elongated zircon grain showing middle-low-luminescent (grey-greyish black)magmatic zoning;(c-e)the zircon grains showing homogeneous middle-low-luminescence (grey-black);(f,g)the zircon grains showing small greyish black-luminescent core and homogeneous lowluminescent (greyish black-black)rim;(h)the zircon grain showing homogeneous low-luminescence (greyish black-black)
圖8 紫蘇石榴黑云二長(zhǎng)片麻巖(BT38-1)鋯石陰極發(fā)光圖像和LA-ICP-MS U-Pb 定年結(jié)果(a-f)鋯石具有核-邊結(jié)構(gòu),繼承性核部具均勻的弱發(fā)光效應(yīng)(灰黑-黑色),變質(zhì)邊具均勻的中等-弱發(fā)光效應(yīng)(灰-灰黑色);(g)鋯石具有相對(duì)均勻的中等發(fā)光效應(yīng)(灰色);(h-j)鋯石具有核-邊結(jié)構(gòu),繼承性核部有均勻的中等-弱發(fā)光效應(yīng)(灰黑-黑色),變質(zhì)邊具均勻的中等-弱發(fā)光效應(yīng)(灰-灰黑色);(k、l)鋯石具有相對(duì)均勻的中等-弱發(fā)光效應(yīng)(灰-灰黑色)Fig.8 CL images and LA-ICP-MS U-Pb ages of zircons from the Hyp-Grt-Bt gneiss (BT38-1)(a-f)the zircon grains showing low-luminescent (greyish black-black)core,middle-low-luminescent (grey-greyish black)rim relationship;(g)the zircon grains showing homogeneous middle-luminescence (grey);(h-j)the zircon grains showing middle-low-luminescent (greyish black-black)core and middle-low-luminescent (grey-greyish black)rim;(k,l)the zircon grains showing homogeneous middle-low-luminescence (grey-greyish black)
圖9 石榴長(zhǎng)英質(zhì)粒狀巖石(BH28-1)鋯石陰極發(fā)光圖像和LA-ICP-MS U-Pb 定年結(jié)果(a)鋯石呈柱狀,具巖漿結(jié)晶環(huán)帶特征,顯示強(qiáng)-中等發(fā)光效應(yīng)(灰白-灰色);(b-j,o)鋯石具有核-邊結(jié)構(gòu),繼承性核部具有中等發(fā)光效應(yīng)(灰-灰黑色),具巖漿結(jié)晶環(huán)帶,變質(zhì)邊具有相對(duì)均勻的弱發(fā)光效應(yīng)(灰黑-黑色);(k-n,p)鋯石具有相對(duì)均勻的弱發(fā)光效應(yīng)(灰黑色-黑色)Fig.9 CL images and LA-ICP-MS U-Pb ages of zircons from the Grt-bearing quartzofeldspathic rock (BH28-1)(a)elongated zircon grain showing high-middle-luminescent (greyish white-grey)magmatic zoning structure;(b-j,o)the zircon grains showing middle-luminescent (grey-greyish black)magmatic zoning core,low-luminescent (greyish black-black)rim relationship;(k-n,p)the zircon grains showing homogeneous low-luminescence (greyish black-black)
石榴長(zhǎng)英質(zhì)粒狀巖石(BH28-1)中的鋯石以渾圓狀或柱狀為主,長(zhǎng)寬比多為1∶1 ~3∶1。鋯石粒徑變化較大(40 ~140μm)。根據(jù)CL 圖像可分為三種類型:其一為繼承性鋯石,多呈柱狀,可具強(qiáng)-中等發(fā)光效應(yīng)(灰白-灰色),內(nèi)部發(fā)育典型的巖漿結(jié)晶環(huán)帶(圖9a);其二具核-邊結(jié)構(gòu),包括繼承性核和相對(duì)弱發(fā)光效應(yīng)(灰黑色-黑色)的變質(zhì)增生邊(圖9b-j,o),核邊之間界限較清晰,其中繼承性核多具中等-弱發(fā)光效應(yīng)(灰色-灰黑色),內(nèi)部可發(fā)育巖漿結(jié)晶環(huán)帶或結(jié)構(gòu)均勻,呈不規(guī)則狀,繼承性核周圍發(fā)育具弱發(fā)光效應(yīng)(灰黑色-黑色)的變質(zhì)增生邊,無分帶特征,變質(zhì)邊寬度變化較大(2 ~80μm);其三為變質(zhì)鋯石,多呈渾圓狀,少數(shù)呈短柱狀,具有相對(duì)均勻的中等-弱發(fā)光效應(yīng)(灰黑-黑色),內(nèi)部無分帶特征,可發(fā)育冷杉葉結(jié)構(gòu)(圖9k-n,p)。
樣品BH27-1 中的繼承性鋯石多含有較高的Th 含量(77×10-6~427 ×10-6)和Th/U 比值(0.19 ~0.85),U 含量相對(duì)較低(160 ×10-6~966 ×10-6),而典型的變質(zhì)鋯石的Th含量(3 ×10-6~153 ×10-6)和Th/U 比值(0.01 ~0.29)均相對(duì)較低,U 含量變化較大(232 ×10-6~2619 ×10-6)(表1)。
207Pb/235U-206Pb/238U 關(guān)系圖解(圖10a)顯示:繼承性鋯石記錄的207Pb/206Pb 年齡為2076 ~2409Ma;變質(zhì)鋯石年齡可分為兩組:(1)記錄的207Pb/206Pb 年齡在1943 ~1947Ma 之間,加權(quán)平均年齡為1946 ±25Ma(MSWD =0.028,n =2;圖10a);值得注意的是BH27-1.37 測(cè)試點(diǎn)的鋯石具有模糊的巖漿結(jié)晶環(huán)帶,而其鋯石年齡為1947 ±16Ma,具有變質(zhì)鋯石的特征,表明該鋯石受到麻粒巖相變質(zhì)作用的改造;(2)記錄的207Pb/206Pb 年齡相對(duì)偏新,為1793 ~1919Ma,加權(quán)平均年齡為1851 ±12Ma(MSWD=2.4,n=26)。
樣品BH27-2 中的繼承性鋯石具有較高的Th 含量(271×10-6~564 ×10-6)和U 含量(351 ×10-6~606 ×10-6),Th/U 比值為0.56 ~1.61,而典型的變質(zhì)鋯石的Th 含量(4 ×10-6~718 ×10-6)和U 含量(253 ×10-6~2313 ×10-6)均變化較大,Th/U 比值(0.00 ~0.48)相對(duì)較低(表2)。
207Pb/235U-206Pb/238U 關(guān)系圖解(圖10b)顯示測(cè)試點(diǎn)均位于諧和線上,該樣品的鋯石年齡顯示:繼承性鋯石記錄的207Pb/206Pb 年齡為2108 ~2262Ma;變質(zhì)鋯石可劃分出兩組年齡:(1)變質(zhì)鋯石記錄的207Pb/206Pb 年齡相對(duì)較老,為1943 ±20Ma(圖10b);(2)變質(zhì)鋯石記錄的207Pb/206Pb 年齡在1817~1927Ma 之間,加權(quán)平均年齡為1864 ±6Ma(MSWD=1.3,n=44;圖10b)。
表1 堇青石榴黑云二長(zhǎng)片麻巖(BH27-1)鋯石LA-ICP-MS 定年結(jié)果Table 1 LA-ICP-MS analyses of zircon from the Crd-Grt-Bt gneiss (Sample BH27-1)
表2 夕線堇青石榴黑云二長(zhǎng)片麻巖(BH27-2)鋯石LA-ICP-MS 定年結(jié)果Table 2 LA-ICP-MS analyses of zircon from the Sil-Crd-Grt gneiss (Sample BH27-2)
表3 紫蘇石榴黑云斜長(zhǎng)片麻巖(BH27-3)鋯石LA-ICP-MS 定年結(jié)果Table 3 LA-ICP-MS analyses of zircon from the Hyp-Grt-Bt gneiss (Sample BH27-3)
圖10 內(nèi)蒙古烏拉山-大青山孔茲巖系樣品的鋯石207Pb/235U-206Pb/238U 年齡關(guān)系圖(a)堇青石榴黑云二長(zhǎng)片麻巖(BH27-1);(b)夕線堇青石榴黑云二長(zhǎng)片麻巖(BH27-2);(c)紫蘇石榴黑云斜長(zhǎng)片麻巖(BH27-3);(d)石榴長(zhǎng)英質(zhì)粒狀巖石(BH28-1);(e)紫蘇石榴黑云二長(zhǎng)片麻巖(BT38-1);(f)夕線堇青石榴黑云二長(zhǎng)片麻巖(BT20-1)Fig.10 207Pb/235U-206Pb/238U diagrams showing U-Pb analyses for zircons of the khondalite rocks in the Wulashan-Daqingshan area(a)Crd-Grt-Bt gneiss (BH27-1);(b)Sil-Crd-Grt gneiss (BH27-2);(c)Hyp-Grt-Bt gneiss (BH27-3);(d)Grt-bearing quartzofeldspathic rock(BH28-1);(e)Hyp-Grt-Bt gneiss (BT38-1);(f)Sil-Crd-Grt gneiss (BT20-1)
樣品BH27-3 中繼承性的鋯石多具有較高的Th 含量(96×10-6~1002 ×10-6),U 含量變化較大(185 ×10-6~1145×10-6),Th/U 比值為0.23 ~1.46,而變質(zhì)鋯石的Th 含量(6×10-6~616 ×10-6)和Th/U 比值(0.01 ~0.49)相對(duì)較低,U 含量變化較大(183 ×10-6~1256 ×10-6)(表3)。
表4 石榴長(zhǎng)英質(zhì)粒狀巖石(BH28-1)鋯石LA-ICP-MS 定年結(jié)果Table 4 LA-ICP-MS analyses of zircon from the Grt-bearing quartzofeldspathic rock (Sample BH28-1)
續(xù)表4Continued Table 4
續(xù)表4Continued Table 4
該樣品鋯石的207Pb/206Pb 年齡可劃分出兩組:繼承性鋯石年齡在2047 ~2463Ma 之間;變質(zhì)鋯石記錄的207Pb/206Pb年齡在1808 ~1924Ma 之間,加權(quán)平均年齡為1863 ±11Ma(MSWD=2.9,n=33;圖10c)。
樣品BH28-1 中繼承性的鋯石多具有較高的Th 含量(35×10-6~763 ×10-6)和Th/U 比值(0.12 ~1.56),U 含量變化較大(61 ×10-6~1040 ×10-6)。變質(zhì)鋯石的Th 含量(5 ×10-6~73 ×10-6)和Th/U 比值(0.01 ~0.13)均相對(duì)較低,U含量變化較大(420 ×10-6~1834 ×10-6)(表4)。
207Pb/235U-206Pb/238U 關(guān)系圖解(圖10d)顯示:繼承性鋯石記錄的207Pb/206Pb 年齡在2076 ~2502Ma 之間;變質(zhì)鋯石記錄的207Pb/206Pb 年齡在1825 ~1922Ma 之間,加權(quán)平均年齡為1858 ±8Ma(MSWD=2.1,n=28;圖10d)。
樣品BT38-1 中繼承性鋯石的Th 含量(6 ×10-6~614 ×10-6)、U 含量(81 ×10-6~1846 ×10-6)和Th/U 比值(0.01~1.67)變化均很大。變質(zhì)鋯石Th 含量(31 ×10-6~214 ×10-6)和U 含量(73 ×10-6~438 ×10-6)相對(duì)較低,Th/U 比值(0.07 ~1.37)變化較大(表5)。
鋯石U-Pb 定年結(jié)果(圖10e)顯示其年齡結(jié)果可劃分出兩組:第一組以繼承性鋯石為代表,記錄的207Pb/206Pb 年齡為2115 ~2499Ma;第二組以變質(zhì)鋯石為代表,其207Pb/206Pb年齡十分集中,變化于1906 ~1962Ma 之間,加權(quán)平均年齡為1946 ±5Ma(MSWD=0.76,n=30;圖10e)。
樣品BT20-1 中繼承性鋯石的Th 含量(16 ×10-6~239×10-6)和U 含量(30 ×10-6~360 ×10-6)以及Th/U 比值(0.06 ~1.08)變化較大。變質(zhì)鋯石的Th 含量(28 ×10-6~117 ×10-6)和Th/U 比值(0.11 ~0.43)相對(duì)較低,U 含量為184 ×10-6~290 ×10-6(表6)。
207Pb/235U-206Pb/238U 關(guān)系圖解(圖10f)顯示,該樣品的鋯石年齡也可劃分出二組:其一以繼承性鋯石為代表,記錄的207Pb/206Pb 年齡為2033 ~2408Ma;其二以變質(zhì)鋯石為代表,記錄的207Pb/206Pb 年齡變化于1929 ~1966Ma 之間,加權(quán)平均年齡為1946 ±12Ma(MSWD=2.9,n=7;圖10f)。
表5 紫蘇石榴黑云二長(zhǎng)片麻巖(BT38-1)鋯石LA-ICP-MS 定年結(jié)果Table 5 LA-ICP-MS analyses of zircon from the Hyp-Grt-Bt gneiss (Sample BT38-1)
續(xù)表5Continued Table 5
表6 夕線堇青石榴黑云二長(zhǎng)片麻巖(BT20-1)鋯石LA-ICP-MS 定年結(jié)果Table 6 LA-ICP-MS analyses of zircon from the Sil-Crd-Grt gneiss (Sample BT20-1)
烏拉山-大青山孔茲巖系巖石的碎屑鋯石年齡變化較大,在2033 ~2502Ma 之間,且不同樣品的年齡分布略有差異,這反映其沉積物源十分復(fù)雜。碎屑鋯石年齡直方圖(圖11)顯示主要峰值年齡分別為:2400 ~2500Ma、~2300Ma 和2000 ~2100Ma,其中,石榴長(zhǎng)英質(zhì)粒狀巖石(BH28-1)的100個(gè)繼承性碎屑鋯石微區(qū)的年代學(xué)測(cè)試結(jié)果顯示兩組207Pb/206Pb 年齡,分別為~2400Ma 和~2100Ma,這與孔茲巖帶其它地區(qū)變泥質(zhì)巖中的碎屑鋯石年齡分布相似(Wan et al.,2006,2009;吳昌華等,2006;Xia et al.,2006a,b,2008;Dong et al.,2007,2013;Yin et al.,2009,2011;周喜文和耿元生,2009)。結(jié)合前人研究資料,認(rèn)為烏拉山-大青山孔茲巖系的最大沉積時(shí)代應(yīng)為~2000Ma。
圖11 烏拉山-大青山孔茲巖系巖石的碎屑鋯石207 Pb/206Pb 年齡直方圖Fig.11 Histogram of the 207Pb/206Pb ages of detrital zircons from the khondalite rocks in the Wulashan-Daqingshan area
盡管部分研究者認(rèn)為華北克拉通孔茲巖帶內(nèi)孔茲巖系巖石的變質(zhì)時(shí)代為新-中太古代(Li et al.,2000;盧良兆,1991;盧良兆等,1992,1996;Qian and Li,1999;楊振升等,2000),越來越多的年代學(xué)研究結(jié)果表明這些孔茲巖系巖石普遍經(jīng)歷了古元古代的高級(jí)變質(zhì)事件(金巍等,1991;李樹勛等,1994;劉喜山,1994,1996;于海峰,1994;金巍和李樹勛,1996;吳昌華等,1998,2006;Zhao et al.,1999,2012;Xia et al.,2006a,b;Wan et al.,2009;Dong et al.,2013)。本文對(duì)孔茲巖帶中段烏拉山-大青山地區(qū)孔茲巖系巖石的鋯石UPb 年代學(xué)研究結(jié)果表明其變質(zhì)時(shí)代為1850 ~1950Ma,證實(shí)了后者的觀點(diǎn)。
烏拉山-大青山孔茲巖系變質(zhì)鋯石的年齡直方圖(圖12)顯示了~1950Ma 和~1860Ma 兩個(gè)主要的年齡峰值。因此,將其變質(zhì)鋯石劃分出兩組變質(zhì)時(shí)代。
(1)~1950Ma。例如,紫蘇石榴黑云二長(zhǎng)片麻巖(BT38-1)的變質(zhì)鋯石記錄的207Pb/206Pb 年齡在1906 ~1962Ma 之間,加權(quán)平均年齡為1946 ±5Ma(圖10e)。夕線石榴黑云斜長(zhǎng)片麻巖(BT20-1)也記錄了近一致的207Pb/206Pb 表面年齡,為1929 ~1966Ma,加權(quán)平均年齡為1946 ±12Ma(圖10f)。此外,堇青石榴黑云二長(zhǎng)片麻巖(BH27-1)的第一組變質(zhì)鋯石記錄的207Pb/206Pb 年齡為1943 ~1947Ma,加權(quán)平均年齡為1946 ±25Ma(圖10a);夕線堇青石榴黑云二長(zhǎng)片麻巖(BH27-2)中第一組變質(zhì)鋯石的207Pb/206Pb 年齡為1943 ±20Ma(圖10b)。
圖12 烏拉山-大青山孔茲巖系巖石中變質(zhì)鋯石的207Pb/206Pb 年齡直方圖Fig. 12 Histogram of the 207Pb/206 Pb ages of the metamorphic zircons from the khondalite rocks in the Wulashan-Daqingshan area
許多研究者通過對(duì)孔茲巖帶其它地區(qū)高級(jí)變質(zhì)巖中的變質(zhì)鋯石開展大量的高精度同位素年代學(xué)研究,也普遍得到了~1950Ma 的變質(zhì)時(shí)代(圖1c;表7;Dong et al.,2007,2013;董春艷等,2009;Wan et al.,2009,2013a;Yin et al.,2009,2011;周喜文和耿元生,2009;Li et al.,2011),進(jìn)一步證實(shí)了內(nèi)蒙孔茲巖系巖石的變質(zhì)作用始于~1950Ma,而并非前人所認(rèn)為的新-中太古代,這可能代表了華北克拉通西部陸塊內(nèi)北部的陰山陸塊和南部的鄂爾多斯陸塊碰撞初始的時(shí)代(Yin et al.,2009,2011;Guo et al.,2012;Zhao et al.,2012;Zhao and Zhai,2013)。
(2)~1860Ma。例如,堇青石榴黑云二長(zhǎng)片麻巖(BH27-1)中第二組變質(zhì)鋯石的207Pb/206Pb 年齡在1793 ~1919Ma 之間,加權(quán)平均年齡為1851 ±12Ma(圖10a);夕線堇青石榴黑云二長(zhǎng)片麻巖(BH27-2)中第二組變質(zhì)鋯石的207Pb/206Pb 年齡為1817 ~1927Ma,加權(quán)平均年齡為1864 ±6Ma(圖10b);紫蘇石榴黑云斜長(zhǎng)片麻巖(BH27-3)變質(zhì)鋯石年齡記錄的207Pb/206Pb 表面年齡為1808 ~1924Ma,加權(quán)平均年齡為1863±11Ma(圖10c);石榴長(zhǎng)英質(zhì)粒狀巖石(BH28-1)的變質(zhì)鋯石記錄的207Pb/206Pb 年齡為1825 ~1922Ma,加權(quán)平均年齡為1858 ±8Ma(圖10d)。其中,對(duì)BH27-1 和BH27-2 樣品的巖相學(xué)觀察顯示,石榴石邊部可出現(xiàn)含堇青石的退變反應(yīng)邊結(jié)構(gòu),反映了峰后近等溫減壓的變質(zhì)階段。
前人研究表明,孔茲巖帶其它地區(qū)變泥質(zhì)巖和變基性巖中的變質(zhì)鋯石記錄了變化于1850 ~1920Ma 之間的變質(zhì)年齡(圖1c、表7;例如:~1870Ma,Yin et al.,2009,2011;周喜文和耿元生,2009;1840 ~1870Ma,Wan et al.,2006;1850 ~1910Ma,Wan et al.,2009;~1892Ma,劉 平 華 等,2013;~1866Ma,Li et al.,2011;~1890Ma,Jiao et al.,2013b;~1912Ma,蔡佳等,2014)。值得注意的是,Xia et al. (2006a)獲得了集寧-卓資地區(qū)的富鋁片麻巖的變質(zhì)年齡為~1810Ma,然而CL 圖像顯示部分繼承性碎屑鋯石的核部實(shí)際上受到變質(zhì)作用的改造,具有變質(zhì)鋯石的特征,因此,該作者將~1940Ma 和~1890Ma 劃分為碎屑鋯石的年齡,實(shí)際上應(yīng)為變質(zhì)年齡。此外,有研究者還報(bào)道了孔茲巖帶超高溫變質(zhì)巖的變質(zhì)時(shí)代為1920 ~1930Ma(Santosh et al.,2007a,b),并認(rèn)為~1920Ma 的超高溫變質(zhì)事件發(fā)生在陰山和鄂爾多斯陸塊碰撞拼合之后,與碰撞后的伸展環(huán)境下地幔巖漿底侵有關(guān)(趙國(guó)春,2009;Peng et al.,2010,2011;Guo et al.,2012;Wan et al.,2013a)。
表7 烏拉山-大青山地區(qū)變泥質(zhì)巖和變基性巖鋯石定年結(jié)果總結(jié)Table 7 Summary of zircon ages of metapelitic rocks and metabasic rocks in the Wulashan-Daqingshan area
續(xù)表7Continued Table 7
最近,Wan et al. (2013a)指出孔茲巖帶變基性巖記錄了四組變質(zhì)年齡,分別為~2450Ma,~1950Ma,~1900Ma 和~1850Ma,均稍晚于相應(yīng)的基性深成巖漿的侵位時(shí)代,可能反映了巖漿弧的環(huán)境(Wells,1980;Bohlen,1991;Condie,1997),這種巖漿弧環(huán)境可能來源于地幔柱(Bohlen,1991)或陸內(nèi)裂谷環(huán)境(Sandiford and Powell,1986)。然而,這種地幔柱或陸內(nèi)裂谷的構(gòu)造模式并不能很好的解釋區(qū)內(nèi)變泥質(zhì)巖指示陸-陸碰撞的近等溫減壓型順時(shí)針P-T 演化軌跡。Liu et al. (2014)也提出烏拉山-大青山變基性巖記錄了2450 ~2500Ma 和1850 ~1950Ma 兩期變質(zhì)事件,其中古元古代變質(zhì)事件又可根據(jù)巖相學(xué)特征和變質(zhì)鋯石包裹體分析,進(jìn)一步劃分出~1950Ma,~1900Ma 和~1850Ma 三個(gè)年齡階段。類似地,Dong et al. (2014)對(duì)大青山的部分孔茲巖系巖石進(jìn)行鋯石U-Pb 年代學(xué)研究,同樣揭示了2400 ~2450Ma 和1900 ~1950Ma 兩期變質(zhì)事件(圖1c),這一結(jié)論與早期研究者認(rèn)為烏拉山-大青山地區(qū)出露的基底再造雜巖經(jīng)歷新太古代晚期-古元古代早期的變質(zhì)事件,隨后又受到古元古代晚期高級(jí)變質(zhì)事件的改造相一致,可能是由于北部的陰山陸塊內(nèi)部分太古宙的構(gòu)造巖片卷入了孔茲巖帶的古元古代構(gòu)造-熱事件(金巍,1989;金巍等,1991;Liu et al.,1993;李樹勛等,1994;劉喜山,1994,1996;于海峰,1994;金巍和李樹勛,1996)。
部分研究者(Yin et al.,2009,2011;趙國(guó)春,2009;周喜文和耿元生,2009;Zhao et al.,2010;Dong et al.,2013)認(rèn)為孔茲巖帶變泥質(zhì)巖的變質(zhì)鋯石所記錄的1850 ~1920Ma 為碰撞后折返抬升的時(shí)代。該時(shí)代與賀蘭山S 型花崗巖的形成時(shí)代相吻合(~1880Ma;Yin et al.,2009),而S 型花崗巖被普遍認(rèn)為是陸-陸碰撞造山后的折返過程中高級(jí)變泥質(zhì)巖減壓熔融的產(chǎn)物(盧良兆等,1992,1996)。此外,Jiao et al.(2013b)提出~1890Ma 的變質(zhì)時(shí)代代表了孔茲巖帶開始折返的時(shí)代。因此,綜合研究表明~1860Ma 應(yīng)代表了北部陰山陸塊和南部鄂爾多斯陸塊碰撞后構(gòu)造折返階段的時(shí)代。注意到,孔茲巖帶不同地體的高級(jí)變質(zhì)巖石記錄的折返時(shí)代與本文~1860Ma 略有差異,可能是由于這些地體的折返時(shí)代略有不同或是各種巖石類型記錄了不同的退變質(zhì)階段的時(shí)代。
前人對(duì)于華北克拉通西北緣孔茲巖帶(或稱豐鎮(zhèn)構(gòu)造帶)新太古代-古元古代時(shí)期的演化歷史和構(gòu)造模式有較大的爭(zhēng)議(Zhao and Zhai,2013)。Zhao et al. (1999,2002,2005,2012)首次提出該孔茲巖帶為一條古元古代陸-陸碰撞型構(gòu)造帶,孔茲巖帶內(nèi)的孔茲巖系巖石形成于被動(dòng)大陸邊緣型環(huán)境,是由其北部的陰山陸塊和南部的鄂爾多斯陸塊于~1950Ma 碰撞拼合并發(fā)生高級(jí)變質(zhì)作用所形成的,陰山陸塊內(nèi)的新太古代-古元古代的閃長(zhǎng)質(zhì)-花崗質(zhì)深成巖和基性火山巖形成于活動(dòng)大陸邊緣。然而,Kusky and Li (2003)則認(rèn)為內(nèi)蒙孔茲巖帶是內(nèi)蒙古-冀北造山帶的一部分,而后者是在~2300Ma 由華北克拉通北緣與外來島弧地體碰撞匯聚后,于1800 ~1900Ma 與另一陸塊碰撞拼合而成的。此后,該研究者(Kusky et al.,2007,Kusky and Santosh,2009)又提出華北克拉通的內(nèi)蒙古-冀北造山帶與哥倫比亞超大陸在1850~1920Ma 發(fā)生碰撞,并發(fā)生高級(jí)變質(zhì)作用。最近,Santosh et al. (2010,2012,2013)指出內(nèi)蒙古縫合帶(孔茲巖帶)形成于大陸增生型環(huán)境,處于板塊匯聚邊緣,并認(rèn)為區(qū)內(nèi)一系列巖漿事件和變質(zhì)事件是俯沖-增生的標(biāo)志。Zhai and Santosh(2011,2013)則認(rèn)為孔茲巖帶與華北克拉通東部陸塊的膠-遼-吉構(gòu)造帶的構(gòu)造模式相似,應(yīng)與陸內(nèi)裂谷的開啟和閉合有關(guān),兩者都經(jīng)歷了陸內(nèi)裂谷作用并形成初始洋盆,隨后經(jīng)歷了陸-陸俯沖碰撞導(dǎo)致洋盆閉合,形成中-高壓麻粒巖相變質(zhì)巖石甚至是超高溫變質(zhì)巖,最后在碰撞后折返抬升的過程,將這些高級(jí)變質(zhì)巖石帶至地殼淺部或是地表。
華北克拉通西北緣孔茲巖帶中段烏拉山-大青山地區(qū)出露大面積孔茲巖系巖石,并保留多種典型的減壓反應(yīng)結(jié)構(gòu),例如:在石榴石周圍形成堇青石的退變反應(yīng)邊結(jié)構(gòu)。Cai et al. (2014)根據(jù)烏拉山-大青山地區(qū)富鋁片麻巖的巖相學(xué)特征,劃分出M1,M2,M3和M4四個(gè)變質(zhì)演化階段的礦物組合,并利用P-T 視剖面圖限定出M1~M4變質(zhì)階段的溫壓條件分別為<780℃和<9kbar,840 ~880℃和9 ~11kbar,800 ~870℃和5.0 ~7.5kbar,<660℃和4.1 ~6.9kbar,經(jīng)歷了峰期麻粒巖相變質(zhì)作用,并建立出近等溫減壓型順時(shí)針的P-T 軌跡。前人對(duì)內(nèi)蒙古孔茲巖帶變泥質(zhì)巖的變質(zhì)作用研究也普遍得到了近一致的順時(shí)針P-T 軌跡(Lu and Jin,1993;Liu et al.,1993;Yin,2010;周喜文等,2010;蔡佳等,2013a;Jiao et al.,2013a;Yin et al.,2014)。其中,部分研究者在孔茲巖帶西段的賀蘭山-千里山地區(qū)發(fā)現(xiàn)了以含藍(lán)晶石+鉀長(zhǎng)石礦物組合為特征的高壓泥質(zhì)麻粒巖,進(jìn)一步利用相平衡模擬建立出近等溫減壓型順時(shí)針P-T 軌跡,峰期變質(zhì)溫壓條件為792 ~805℃和10.2 ~11.2kbar(Yin,2010;周喜文等,2010;Yin et al.,2014)。Jiao et al. (2013a)對(duì)孔茲巖帶東段的集寧小什字地區(qū)石榴石花崗巖進(jìn)行了詳細(xì)的變質(zhì)作用研究,劃分出了M1,M2和M3三個(gè)變質(zhì)階段,利用金紅石Zr 溫度計(jì)和P-T 視剖面手段綜合限定各變質(zhì)階段的溫壓條件分別為820 ~850℃(最高可達(dá)950℃)和8.5 ~9.5kbar,850 ~865℃和7.4 ~7.6kbar,710 ~720℃和6.4 ~6.6kbar,同樣得到了典型的近等溫減壓型的順時(shí)針P-T 軌跡。此外,近年來一些研究者對(duì)大青山-烏拉山的東坡地區(qū)和土貴烏拉、和林格爾、土貴山等地區(qū)零星出露的超高溫變質(zhì)巖的變質(zhì)演化、成因機(jī)制、同位素年代學(xué)等方面進(jìn)行了深入研究(Santosh et al.,2006,2007a,b,2008,2009a,b,2012;Peng et al.,2010,2011,2012;Jiao and Guo,2011;Tsunogae et al.,2011;Guo et al.,2012;Liu et al.,2012),對(duì)于該區(qū)超高溫變質(zhì)巖所經(jīng)歷的P-T 軌跡樣式仍存在不同認(rèn)識(shí),其中Santosh et al.(2009b)認(rèn)為土貴烏拉超高溫變質(zhì)巖經(jīng)歷了逆時(shí)針的P-T軌跡(峰期變質(zhì)溫度>950℃),而Guo et al. (2012)則認(rèn)為東坡超高溫變質(zhì)巖記錄了順時(shí)針的P-T 軌跡(峰期溫度為910 ~980℃),然而,二者的P-T 軌跡均具有近等溫減壓的變質(zhì)階段。
有研究者認(rèn)為這種近等溫減壓型的順時(shí)針P-T 演化軌跡與地殼擠壓增厚有關(guān),反映了陸-陸碰撞造山過程中加厚下地殼折返至地表的動(dòng)力學(xué)過程,顯示出巖石經(jīng)歷的一系列構(gòu)造-熱事件(England and Thompson,1984;Thompson and England,1984;Condie et al.,1992;Brown,1993)。因此,上述對(duì)內(nèi)蒙古孔茲巖帶變泥質(zhì)巖的變質(zhì)作用研究獲得的近等溫減壓型順時(shí)針P-T 軌跡進(jìn)一步支持了孔茲巖帶的碰撞拼合模式(Zhao et al.,2005),即俯沖-碰撞作用造成陸殼的加厚,向下俯沖的加厚陸殼物質(zhì)被埋深至下地殼并經(jīng)歷峰期中-高壓麻粒巖相變質(zhì)作用的改造,隨后變質(zhì)地殼發(fā)生折返抬升至地殼淺部。這一模式可以較好地解釋變泥質(zhì)巖如何從地表被帶至下地殼后又折返至地表的構(gòu)造演化過程以及伴隨麻粒巖相變質(zhì)作用的成因機(jī)制(Zhao et al.,2012)。
結(jié)合前人研究資料,烏拉山-大青山孔茲巖系巖石所記錄的古元古代高級(jí)變質(zhì)事件可能經(jīng)歷了陸-陸俯沖-碰撞和碰撞后折返抬升的造山過程,進(jìn)一步支持了孔茲巖帶的碰撞拼合模式(Zhao et al.,2005),表明華北克拉通西部的陰山陸塊和鄂爾多斯陸塊之間在~1950Ma 開始發(fā)生俯沖-碰撞作用,形成了古元古代的一條陸-陸碰撞構(gòu)造帶,普遍發(fā)生麻粒巖相變質(zhì)的孔茲巖系巖石由此產(chǎn)生,并在~1860Ma 經(jīng)歷折返抬升至地殼淺部,即經(jīng)歷了減壓的退變質(zhì)過程。
對(duì)烏拉山-大青山孔茲巖系巖石的巖相學(xué)特征、鋯石內(nèi)部結(jié)構(gòu)分析和鋯石U-Pb 年代學(xué)的綜合研究,得出以下幾點(diǎn)認(rèn)識(shí):
(1)烏拉山-大青山孔茲巖系巖石如夕線堇青石榴二長(zhǎng)片麻巖保留了典型的減壓反應(yīng)結(jié)構(gòu),其碎屑鋯石的年齡變化于2033 ~2502Ma 之間,主要分為三組年齡2400 ~2500Ma、~2300Ma 和2000 ~2100Ma,最大沉積時(shí)代應(yīng)為~2000Ma;
(2)烏拉山-大青山孔茲巖系巖石的變質(zhì)時(shí)代為1850 ~1950Ma,其年齡峰值主要集中在~1950Ma 和~1860Ma;
(3)烏拉山-大青山孔茲巖系巖石卷入了華北克拉通西部的古老陸塊之間的碰撞造山作用過程中,其中~1950Ma代表了陰山陸塊和鄂爾多斯陸塊間發(fā)生初始的俯沖-碰撞作用的時(shí)間,并形成了古元古代的一條陸-陸碰撞構(gòu)造帶,即孔茲巖帶,在此期間,孔茲巖帶普遍經(jīng)歷了麻粒巖相變質(zhì)作用;隨后于~1860Ma 左右,孔茲巖帶麻粒巖相變質(zhì)巖石折返抬升至地殼淺部,并疊加了后期退變質(zhì)作用的改造。
致謝 天津地質(zhì)礦產(chǎn)研究所同位素實(shí)驗(yàn)室耿建珍老師在鋯石的LA-ICP-MS U-Pb 定年測(cè)試過程中給予了指導(dǎo)和幫助;中國(guó)地質(zhì)科學(xué)院地質(zhì)研究所劉超輝博士和肖玲玲博士在野外提供了很大的幫助;吳春明教授和另一名匿名審稿人對(duì)本文提出了寶貴的修改意見;在此一并表示衷心感謝。
Bohlen SR. 1991. On the formation of granulites. Journal of Metamorphic Geology,9(3):223 -229
Brown M. 1993. P-T-t evolution of orogenic belts and the causes of regional metamorphism. Journal of the Geological Society,150(2):227 -241
Cai J,Liu PH,Liu FL,Liu JH,Wang F and Shi JR. 2013a. Genetic mineralogy and metamorphic evolution of Al-rich gneisses in the Shiguai area,Daqingshan-Wulashan metamorphic complex belt.Acta Petrologica Sinica,29 (2):437 - 461 (in Chinese with English abstract)Cai J,Liu FL,Liu PH,Shi JR and Liu JH. 2013b. Petrogenesis and metamorphic P-T conditions of garnet-spinel-biotite-bearing paragneiss in Danangou area,Daqingshan-Wulashan metamorphic complex belt. Acta Petrologica Sinica,29(7):2313 - 2328 (in Chinese with English abstract)
Cai J,Liu FL,Liu PH,Liu CH,Wang F and Shi JR. 2014.Metamorphic P-T path and tectonic implications of pelitic granulites from the Daqingshan Complex of the Khondalite Belt,North China Craton. Precambrian Research,241:161 -184
Cai J,Liu FL,Liu PH and Shi JR. 2014. Metamorphic P-T conditions and U-Pb dating of the sillimanite-cordierite-garnet paragneisses in Sanchakou,Jining area,Inner Mongolia. Acta Petrologica Sinica,30(2):472 -490 (in Chinese with English abstract)
Condie KC,Boryta MD,Liu JZ and Qian XL. 1992. The origin of khondalites:Geochemical evidence from the Archean to Early Proterozoic granulite belt in the North China craton. Precambrian Research,59(3 -4):207 -223
Condie KC. 1997. Contrasting sources for upper and lower continental crust:The greenstone connection. The Journal of Geology,105(6):729 -736
Dan W,Li XH,Guo JH,Liu Y and Wang XC. 2012. Integrated in situ zircon U-Pb age and Hf-O isotopes for the Helanshan khondalites in North China Craton:Juvenile crustal materials deposited in active or passive continental margin?Precambrian Research,222 -223:143-158
Dong CY,Liu DY,Li JJ,Wan YS,Zhou HY,Li CD,Yang YH and Xie LW. 2007. Palaeoproterozoic Khondalite Belt in the western North China Craton:New evidence from SHRIMP dating and Hf isotope composition of zircons from metamorphic rocks in the Bayan Ul-Helan Mountains area. Chinese Science Bulletin,52(21):2984 -2994
Dong CY,Liu DY,Wan YS,Xu ZY,Liu ZH and Yang ZS. 2009.Crustally derived carbonatite from the Daqinshan area:Zircon features and SHRIMP dating. Acta Geologica Sinica,83(3):388 -398 (in Chinese with English abstract)
Dong CY,Wan YS,Xu ZY,Liu DY,Yang ZS,Ma MZ and Xie HQ.2013. SHRIMP zircon U-Pb dating of Late Paleoproterozoic kondalites in the Daqing Mountains area on the North China Craton.Science China (Earth Sciences),56(1):115 -125
Dong CY,Wan YS,Wilde SA,Xu ZY,Ma MZ,Xie HQ and Liu DY.2014. Earliest Paleoproterozoic supracrustal rocks in the North China Craton recognized from the Daqingshan area of the Khondalite Belt:Constraints on craton evolution. Gondwana Research,25(4):1535-1553
England PC and Thompson AB. 1984. Pressure-temperature-time paths of regional metamorphism I. Heat transfer during the evolution of regions of thickened continental crust. Journal of Petrology,25(4):894 -928
Geng JZ,Zhang J,Li HK,Li HM,Zhang YQ and Hao S. 2012. Tenmicron-sized zircon U-Pb dating using LA-MC-ICP-MS. Acta Geoscientia Sinica,33(6):877 - 884 (in Chinese with English abstract)
Guo JH,Peng P,Chen Y,Jiao SJ and Windley BF. 2012. UHT sapphirine granulite metamorphism at 1. 93 ~1. 92Ga caused by gabbronorite intrusions:Implications for tectonic evolution of the northern margin of the North China Craton. Precambrian Research,222 -223:124 -142
Jiao SJ and Guo JH. 2011. Application of the two-feldspar geothermometer to ultrahigh-temperature (UHT) rocks in the Khondalite belt,North China craton and its implications. American Mineralogist,96(2 -3):250 -260
Jiao SJ,Guo JH,Harley SL and Windley BF. 2013a. New constraints from garnetite on the P-T path of the Khondalite Belt:Implications for the tectonic evolution of the North China Craton. Journal of Petrology,54(9):1725 -1758
Jiao SJ,Guo JH,Harley SL and Peng P. 2013b. Geochronology and trace element geochemistry of zircon,monazite and garnet from the garnetite and/or associated other high-grade rocks:Implications for Palaeoproterozoic tectonothermal evolution of the Khondalite Belt,North China Craton. Precambrian Research,237:78 -100 Jin W. 1989. Geological evolution and metamorphic dynamics of Early Precambrian basement rocks along the northern boundary (central section) of the North China Craton. Ph. D. Dissertation.Changchun:Changchun College of Geology (in Chinese with English summary)
Jin W,Li SX and Liu XS. 1991. A study on characteristics of Early Precambrian high-grade metamorphic rock series and their metamorphic dynamics. Acta Petrologica Sinica,(4):27 -35 (in Chinese with English abstract)
Jin W and Li SX. 1996. PTt path and crustal thermodynamic model of Late Archean-Early Proterozoic high-grade metamorphic terrain in North China. Acta Petrologica Sinica,12(2):208 - 221 (in Chinese with English abstract)
Kusky TM and Li JH. 2003. Paleoproterozoic tectonic evolution of the North China Craton. Journal of Asian Earth Sciences,22(4):383-397
Kusky TM,Li JH and Santosh M. 2007. The Paleoproterozoic North Hebei orogen:North China Craton’s collisional suture with the Columbia supercontinent. Gondwana Research,12(1 -2):4 -28
Kusky TM and Santosh M. 2009. The Columbia connection in North China. Geological Society,London,Special Publications,323(1):49 -71
Li JH,Qian XL and Liu SW. 2000. Geochemistry of khondalites from the central portion of North China craton (NCC):Implications for the continental cratonization in the Neoarchean. Science in China(Series D),43(3):253 -265
Li SX,Xu XC,Liu XS and Sun YD. 1994. Early Precambrian Geology of Wulashan Region,Inner Mongolia. Beijing:Geological Publishing House,1 -78 (in Chinese)
Li XP, Yang ZY, Zhao GC, Grapes R and Guo JH. 2011.Geochronology of khondalite-series rocks of the Jining Complex:Confirmation of depositional age and tectonometamorphic evolution of the North China craton. International Geology Review,53(10):1194 -1211
Liu FL,Shen QH,Geng YS,Xu XC and Ma R. 1998. Genetic relationship of metamorphic reaction and dehydration-melting:Example from Al-rich gneiss of khondalite series on the border of Jin(Shanxi Province)-Inner Mongolia. Science in China (Series D),41(1):49 -56
Liu FL,Shen QH and Zhao ZR. 2002. Evolution of mineral assemblages of khondalite series in the process of prograde metamorphism,southeastern Inner Mongolia:Evidence from mineral inclusions in zircons. Geological Bulletin of China,21(2):75 -78 (in Chinese with English abstract)
Liu PH,Liu FL,Cai J,Liu JH,Shi JR and Wang F. 2013.Geochronological and geochemical study of the Lijiazi mafic granulites from the Daqingshan-Wulashan metamorphic complex,the central Khondalite Belt in the North China Craton. Acta Petrologica Sinica,29(2):462 -484 (in Chinese with English abstract)
Liu PH,Liu FL,Liu CH,Liu JH,Wang F,Xiao LL,Cai J and Shi JR.2014. Multiple mafic magmatic and high-grade metamorphic events revealed by zircons from meta-mafic rocks in the Daqingshan-Wulashan Complex of the Khondalite Belt,North China Craton.Precambrian Research,246:334 -357
Liu SJ,Tsunogae T,Li WS,Shimizu H,Santosh M,Wan YS and Li JH. 2012. Paleoproterozoic granulites from Heling’er:Implications for regional ultrahigh-temperature metamorphism in the North China Craton. Lithos,148:54 -70
Liu SJ,Dong CY,Xu ZY,Santosh M,Ma MZ,Xie HQ,Liu DY and Wan YS. 2013. Palaeoproterozoic episodic magmatism and highgrade metamorphism in the North China Craton:Evidence from SHRIMP zircon dating of magmatic suites in the Daqingshan area.Geological Journal,48(5):429 -455
Liu XS,Jin W,Li SX and Xu XC. 1993. Two types of Precambrian high-grade metamorphism,Inner Mongolia, China. Journal of Metamorphic Geology,11(4):499 -510
Liu XS. 1994. Characteristics of basement reworked complex and implication for Daqingshan orogenic belt. Acta Pertologica Sinica,10(4):413 -426 (in Chinese with English abstract)
Liu XS. 1996. Progressive metamorphic genesis of Archean granulites in Central Nei Mongol. Acta Petrologica Sinica,12(2):287 -298 (in Chinese with English abstract)
Lu LZ. 1991. Metamorphic P-T-t path of the Archean granulite-facies terrains in Jining area,Inner Mongolia and its tectonic implications.Acta Petrologica Sinica,(4):1 - 12 (in Chinese with English abstract)
Lu LZ,Jin SQ,Xu XC and Liu FL. 1992. The Petrogenesis and Orebearing Potential of Precambrian Khondalite Series in Southeast Inner Mongolia. Changchun:Jilin Science and Technology Press,4 -121(in Chinese)
Lu LZ and Jin SQ. 1993. P-T-t paths and tectonic history of an Early Precambrian granulite facies terrane,Jining district,south-east Inner Mongolia,China. Journal of Metamorphic Geology,11(4):483-498
Lu LZ,Xu XC and Liu FL. 1996. The Early Precambrian Khondalite Series in the North China. Changchun:Changchun Publishing House,16 -118 (in Chinese)
Ma MZ,Wan YS,Santosh M,Xu ZY,Xie HQ,Dong CY,Liu DY and Guo CL. 2012. Decoding multiple tectonothermal events in zircons from single rock samples:SHRIMP zircon U-Pb data from the Late Neoarchean rocks of Daqingshan,North China Craton. Gondwana Research,22(3 -4):810 -827
Peng P,Guo JH,Zhai MG and Bleeker W. 2010. Paleoproterozoic gabbronoritic and granitic magmatism in the northern margin of the North China craton: Evidence of crust-mantle interaction.Precambrian Research,183(3):635 -659
Peng P,Guo JH,Windley BF and Li XH. 2011. Halaqin volcanosedimentary succession in the central-northern margin of the North China Craton:Products of Late Paleoproterozoic ridge subduction.Precambrian Research,187(1 -2):165 -180
Peng P,Guo JH,Zhai MG,Windley BF,Li TS and Liu F. 2012.Genesis of the Hengling magmatic belt in the North China Craton:Implications for Paleoproterozoic tectonics. Lithos,148:27 -44
Qian XL and Li JH. 1999. Discovery of Neoarchean unconformity and its implication for continental cratonization of North China craton.Science in China (Series D),42(4):399 -407
Sandiford M and Powell R. 1986. Deep crustal metamorphism during continental extension:Modern and ancient examples. Earth and Planetary Science Letters,79(1 -2):151 -158
Santosh M,Sajeev K and Li JH. 2006. Extreme crustal metamorphism during Columbia supercontinent assembly:Evidence from North China Craton. Gondwana Research,10(3 -4):256 -266
Santosh M,Tsunogae T,Li JH and Liu SJ. 2007a. Discovery of sapphirine-bearing Mg-Al granulites in the North China Craton:Implications for Paleoproterozoic ultrahigh temperature metamorphism. Gondwana Research,11(3):263 -285
Santosh M,Wilde SA and Li JH. 2007b. Timing of Paleoproterozoic ultrahigh-temperature metamorphism in the North China Craton:Evidence from SHRIMP U-Pb zircon geochronology. Precambrian Research,159(3 -4):178 -196
Santosh M,Tsunogae T,Ohyama H,Sato K,Li JH and Liu SJ. 2008.Carbonic metamorphism at ultrahigh-temperatures:Evidence from North China Craton. Earth and Planetary Science Letters,266(1 -2):149 -165
Santosh M,Wan YS,Liu DY,Dong CY and Li JH. 2009a. Anatomy of zircons from an ultrahot orogen:The amalgamation of the North China craton within the supercontinent Columbia. The Journal of Geology,117(4):429 -443
Santosh M, Sajeev K, Li JH, Liu SJ and Itaya T. 2009b.Counterclockwise exhumation of a hot orogen:The Paleoproterozoic ultrahigh-temperature granulites in the North China Craton. Lithos,110(1 -4):140 -152
Santosh M,Zhao DP and Kusky TM. 2010. Mantle dynamics of the Paleoproterozoic North China Craton:A perspective based on seismic tomography. Journal of Geodynamics,49(1):39 -53
Santosh M,Liu SJ,Tsunogae T and Li JH. 2012. Paleoproterozoic ultrahigh-temperature granulites in the North China Craton:Implications for tectonic models on extreme crustal metamorphism.Precambrian Research,222 -223:70 -106
Santosh M,Liu DY,Shi YL and Liu SJ. 2013. Paleoproterozoic accretionary orogenesis in the North China Craton:A SHRIMP zircon study. Precambrian Research,227:29 -54
Thompson AB and England PC. 1984. Pressure-temperature-time paths of regional metamorphism II. Their inference and interpretation using mineral assemblages in metamorphic rocks. Journal of Petrology,25(4):929 -955
Tsunogae T,Liu SJ,Santosh M,Shimizu H and Li JH. 2011. Ultrahightemperature metamorphism in Daqingshan,Inner Mongolia Suture Zone,North China Craton. Gondwana Research,20(1):36 -47
Wan YS,Song B,Liu DY,Wilde SA,Wu JS,Shi YR,Yin XY and Zhou HY. 2006. SHRIMP U-Pb zircon geochronology of Palaeoproterozoic metasedimentary rocks in the North China Craton:Evidence for a major Late Palaeoproterozoic tectonothermal event.Precambrian Research,149(3 -4):249 -271
Wan YS,Liu DY,Dong CY,Xu ZY,Wang ZJ,Wilde SA,Yang YH,Liu ZH and Zhou H. 2009. The Precambrian Khondalite Belt in the Daqingshan area,North China Craton:Evidence for multiple metamorphic events in the Palaeoproterozoic era. Geological Society,London,Special Publications,323(1):73 -97
Wan YS,Xu ZY,Dong CY,Nutman A,Ma MZ,Xie HQ,Liu SJ,Liu DY,Wang HC and Cu H. 2013a. Episodic Paleoproterozoic(~2.45,~1.95 and ~1.85Ga)mafic magmatism and associated high temperature metamorphism in the Daqingshan area,North China Craton:SHRIMP zircon U-Pb dating and whole-rock geochemistry.Precambrian Research,224:71 -93
Wan YS,Xie HQ,Yang H,Wang ZJ,Liu DL,Kr?ner A,Wilde SA,Geng YS,Sun LY,Ma MZ,Liu SJ,Dong CY and Du LL. 2013b.Is the Ordos Block Archean or Paleoproterozoic in age?Implications for the Precambrian evolution of the North China Craton. American Journal of Science,313(7):683 -711
Wang F, Li XP, Chu H and Zhao GC. 2011. Petrology and metamorphism of khondalites from the Jining complex,North China craton. International Geology Review,53(2):212 -229
Wells PRA. 1980. Thermal models for the magmatic accretion and subsequent metamorphism of continental crust. Earth and Planetary Science Letters,46(2):253 -265
Whitney DL and Evans BW. 2010. Abbreviations for names of rockforming minerals. American Mineralogist,95(1):185 -187
Wu CH,Li HM,Zhong CT and Chen QA. 1998. The ages of zircon and rutile (cooling)from khondalite in Huangtuyao,Inner Mongolia.Geological Review,44(6):618 - 626 (in Chinese with English abstract)
Wu CH,Sun M,Li HM,Zhao GC and Xia XP. 2006. LA-ICP-MS U-Pb zircon ages of the khondalites from the Wulashan and Jining highgrade terrain in northern margin of the North China Craton:Constraints on sedimentary age of the khondalite. Acta Petrologica Sinica,22(11):2639 -2654 (in Chinese with English abstract)
Xia XP,Sun M,Zhao GC and Luo Y. 2006a. LA-ICP-MS U-Pb geochronology of detrital zircons from the Jining Complex,North China Craton and its tectonic significance. Precambrian Research,144(3 -4):199 -212
Xia XP,Sun M,Zhao GC,Wu FY,Xu P,Zhang JP and Luo Y.2006b. U-Pb and Hf isotopic study of detrital zircons from the Wulashan khondalites:Constraints on the evolution of the Ordos Terrane,Western Block of the North China Craton. Earth and Planetary Science Letters,241(3 -4):581 -593
Xia XP,Sun M,Zhao GC,Wu FY,Xu P,Zhang J and He YH. 2008.Paleoproterozoic crustal growth in the Western Block of the North China Craton:Evidence from detrital zircon Hf and whole rock Sr-Nd isotopic compositions of the khondalites from the Jining Complex.American Journal of Science,308(3):304 -327
Xu ZY,Liu ZH,Yang ZS,Wu XW and Chen XF. 2007. Structure of metamorphic strata of the Khondalite Series in the Daqingshan-Wulashan area, central Inner Mongolia, China, and their geodynamic implications. Geological Bulletin of China,26(5):526-536 (in Chinese with English abstract)
Yang ZS,Xu ZY and Liu ZH. 2000. Khondalite event and Archean crust structure evolvement. Progress in Precambrian Research,23(4):206 -212 (in Chinese with English abstract)
Yin CQ,Zhao GC,Sun M,Xia XP,Wei CJ,Zhou XW and Leung WH.2009. LA-ICP-MS U-Pb zircon ages of the Qianlishan Complex:Constrains on the evolution of the Khondalite Belt in the Western Block of the North China Craton. Precambrian Research,174(1 -2):78 -94
Yin CQ. 2010. Metamorphism of the Helanshan-Qianlishan Complex and its implications for tectonic evolution of the Khondalite Belt in the Western Block,North China Craton. Ph. D. Dissertation. Hong Kong:The University of Hong Kong
Yin CQ,Zhao GC,Guo JH,Sun M,Xia XP,Zhou XW and Liu CH.2011. U-Pb and Hf isotopic study of zircons of the Helanshan Complex:Constrains on the evolution of the Khondalite Belt in the Western Block of the North China Craton. Lithos,122(1 -2):25-38
Yin CQ,Zhao GC,Wei CJ,Sun M,Guo JH and Zhou XW. 2014.Metamorphism and partial melting of high-pressure pelitic granulites from the Qianlishan Complex:Constraints on the tectonic evolution of the Khondalite Belt in the North China Craton. Precambrian Research,242:172 -186
Yu HF. 1994. High temperature deformational-metamorphic zone and Early Proterozoic inner continental orogeny. Ph. D. Dissertation.Changchun:Changchun College of Geology (in Chinese with English summary)
Zhai MG,Bian AG and Zhao TP. 2000. The amalgamation of the supercontinent of North China Craton at the end of Neo-Archaean and its breakup during Late Palaeoproterozoic and Meso-Proterozoic.Science in China (Series D),43(Suppl.1):219 -232
Zhai MG and Santosh M. 2011. The Early Precambrian odyssey of the North China Craton:A synoptic overview. Gondwana Research,20(1):6 -25
Zhai MG and Santosh M. 2013. Metallogeny of the North China Craton:Link with secular changes in the evolving Earth. Gondwana Research,24(1):275 -297
Zhao GC,Wilde SA,Cawood PA and Lu LZ. 1999. Tectonothermal history of the basement rocks in the western zone of the North China Craton and its tectonic implications. Tectonophysics,310(1 -4):37 -53
Zhao GC,Cawood PA,Wilde SA and Sun M. 2002. Review of global 2.1 ~1.8Ga orogens:Implications for a pre-Rodinia supercontinent.Earth-Science Reviews,59(1 -4):125 -162
Zhao GC,Sun M and Wilde SA. 2003. Major tectonic units of the North China Craton and their Paleoproterozoic assembly. Science in China(Series D),46(1):23 -38
Zhao GC,Sun M,Wilde SA and Li SZ. 2005. Late Archean to Paleoproterozoic evolution of the North China Craton:Key issues revisited. Precambrian Research,136(2):177 -202
Zhao GC. 2009. Metamorphic evolution of major tectonic units in the basement of the North China Craton:Key issues and discussion.Acta Petrologica Sinica,25(8):1772 - 1792 (in Chinese with English abstract)
Zhao GC,Wilde SA. Guo JH,Cawood PA,Sun M and Li XP. 2010.Single zircon grains record two Paleoproterozoic collisional events in the North China Craton. Precambrian Research,177(3 -4):266 -276
Zhao GC,Cawood PA,Li SZ,Wilde SA,Sun M,Zhang J,He YH and Yin CY. 2012. Amalgamation of the North China Craton:Key issues and discussion. Precambrian Research,222 -223:55 -76
Zhao GC and Zhai MG. 2013. Lithotectonic elements of Precambrian basement in the North China Craton: Review and tectonic implications. Gondwana Research,23(4):1207 -1240
Zhou XW and Geng YS. 2009. Metamorphic age of the khondalite series in the Helanshan region:Constraints on the evolution of the western block in the North China Craton. Acta Petrologica Sinica,25(8):1843 -1852 (in Chinese with English abstract)
Zhou XW,Zhao GC and Geng YS. 2010. Helanshan high pressure pelitic granulite:Petrologic evidence for collision event in the western block of the North China Craton. Acta Petrologica Sinica,26(7):2113 -2121 (in Chinese with English abstract)
附中文參考文獻(xiàn)
蔡佳,劉平華,劉福來,劉建輝,王舫,施建榮. 2013a. 大青山-烏拉山變質(zhì)雜巖帶石拐地區(qū)富鋁片麻巖成因礦物學(xué)與變質(zhì)演化. 巖石學(xué)報(bào),29(2):437 -461
蔡佳,劉福來,劉平華,施建榮,劉建輝. 2013b. 大青山-烏拉山變質(zhì)雜巖帶大南溝地區(qū)含榴尖晶黑云鉀長(zhǎng)片麻巖成因及其形成的P-T 條件. 巖石學(xué)報(bào),29(7):2313 -2328
蔡佳,劉福來,劉平華,施建榮. 2014. 內(nèi)蒙古集寧三岔口地區(qū)夕線堇青石榴二長(zhǎng)片麻巖變質(zhì)作用及年代學(xué)研究. 巖石學(xué)報(bào),30(2):472 -490
董春艷,劉敦一,萬渝生,徐仲元,劉正宏,楊振升. 2009. 大青山地區(qū)古元古代殼源碳酸巖:鋯石特征及SHRIMP 定年. 地質(zhì)學(xué)報(bào),83(3):388 -398
耿建珍,張健,李懷坤,李惠民,張永清,郝爽. 2012. 10μm 尺度鋯石U-Pb 年齡的LA-MC-ICP-MS 測(cè)定. 地球?qū)W報(bào),33(6):877-884
金巍. 1989. 華北陸臺(tái)北緣(中段)早前寒武紀(jì)地質(zhì)演化及其變質(zhì)動(dòng)力學(xué)研究. 博士學(xué)位論文. 長(zhǎng)春:長(zhǎng)春地質(zhì)學(xué)院
金巍,李樹勛,劉喜山. 1991. 內(nèi)蒙大青山地區(qū)早前寒武紀(jì)高級(jí)變質(zhì)巖系特征和變質(zhì)動(dòng)力學(xué). 巖石學(xué)報(bào),(4):27 -35
金巍,李樹勛. 1996. 華北晚太古代-早元古代高級(jí)變質(zhì)區(qū)的變質(zhì)PT-t 軌跡及其地殼熱動(dòng)力學(xué)演化模式. 巖石學(xué)報(bào),12(2):208-221
李樹勛,徐學(xué)純,劉喜山,孫德育. 1994. 內(nèi)蒙古烏拉山區(qū)早前寒武紀(jì)地質(zhì). 北京:地質(zhì)出版社,1 -78
劉福來,沈其韓,趙子然. 2002. 內(nèi)蒙古東南部孔茲巖系進(jìn)變質(zhì)過程礦物組合演化——來自鋯石中礦物包裹體的證據(jù). 地質(zhì)通報(bào),21(2):75 -78
劉平華,劉福來,蔡佳,劉建輝,施建榮,王舫. 2013. 華北克拉通孔茲巖帶中段大青山-烏拉山變質(zhì)雜巖立甲子基性麻粒巖年代學(xué)及地球化學(xué)研究. 巖石學(xué)報(bào),29(2):462 -484
劉喜山. 1994. 大青山造山帶中基底再造雜巖的特征及其指示意義.巖石學(xué)報(bào),10(4):413 -426
劉喜山. 1996. 內(nèi)蒙古中部太古代麻粒巖遞增變質(zhì)成因. 巖石學(xué)報(bào),12(2):287 -298
盧良兆. 1991. 內(nèi)蒙集寧地區(qū)太古宙麻粒巖相變質(zhì)作用的PTt 軌跡及其大地構(gòu)造意義. 巖石學(xué)報(bào),(4):1 -12
盧良兆,靳是琴,徐學(xué)純,劉福來. 1992. 內(nèi)蒙古東南部早前寒武紀(jì)孔茲巖系成因及其含礦性. 長(zhǎng)春:吉林科學(xué)技術(shù)出版社,4-121
盧良兆,徐學(xué)純,劉福來. 1996. 中國(guó)北方早前寒武紀(jì)孔茲巖系. 長(zhǎng)春:長(zhǎng)春出版社,16 -118
吳昌華,李惠民,鐘長(zhǎng)汀,陳強(qiáng)安. 1998. 內(nèi)蒙古黃土窯孔茲巖系的鋯石與金紅石年齡研究. 地質(zhì)論評(píng),44(6):618 -626
吳昌華,孫敏,李惠民,趙國(guó)春,夏小平. 2006. 烏拉山-集寧孔茲巖鋯石激光探針等離子質(zhì)譜(LA-ICP-MS)年齡——孔茲巖沉積時(shí)限的年代學(xué)研究. 巖石學(xué)報(bào),22(11):2639 -2654
徐仲元,劉正宏,楊振升,吳新偉,陳曉峰. 2007. 內(nèi)蒙古中部大青山-烏拉山地區(qū)孔茲巖系的變質(zhì)地層結(jié)構(gòu)及動(dòng)力學(xué)意義. 地質(zhì)通報(bào),26(5):526 -536
楊振升,徐仲元,劉正宏. 2000. 孔茲巖系事件與太古宙地殼構(gòu)造演化. 前寒武紀(jì)研究進(jìn)展,23(4):206 -212
于海峰. 1994. 大青山地區(qū)高溫變形變質(zhì)帶與早元古代陸內(nèi)造山作用. 博士學(xué)位論文. 長(zhǎng)春:長(zhǎng)春地質(zhì)學(xué)院
趙國(guó)春. 2009. 華北克拉通基底主要構(gòu)造單元變質(zhì)作用演化及其若干問題討論. 巖石學(xué)報(bào),25(8):1772 -1792
周喜文,耿元生. 2009. 賀蘭山孔茲巖系的變質(zhì)時(shí)代及其對(duì)華北克拉通西部陸塊演化的制約. 巖石學(xué)報(bào),25(8):1843 -1852
周喜文,趙國(guó)春,耿元生. 2010. 賀蘭山高壓泥質(zhì)麻粒巖——華北克拉通西部陸塊拼合的巖石學(xué)證據(jù). 巖石學(xué)報(bào),26(7):2113-2121