地球学报
地毬學報
지구학보
ACTA GEOSCIENTIA SINICA
2013年
6期
680-690
,共11页
王居里%杨猛%王建其%党飞鹏
王居裏%楊猛%王建其%黨飛鵬
왕거리%양맹%왕건기%당비붕
花岗闪长斑岩%LA-ICP-MS锆石U-Pb定年%早奥陶世陆缘弧%中天山北缘
花崗閃長斑巖%LA-ICP-MS鋯石U-Pb定年%早奧陶世陸緣弧%中天山北緣
화강섬장반암%LA-ICP-MS고석U-Pb정년%조오도세륙연호%중천산북연
granodiorite-porphyry%zircon LA-ICP-MS U-Pb dating%Early Ordovician epicontinental arc%northern margin of Middle Tianshan Mountains
古伦沟地区古仍格萨拉东花岗闪长斑岩体位于中天山构造带北缘。地球化学和锆石 U-P 年龄测定结果显示：岩石高碱富 Na、贫 Fe 和 Mg、弱过铝质(ACNK=0.98~1.11),稀土总量较低(∑REE=61.28×10-6~99.50×10-6)且分异明显(LaN/YbN=7.82~22.80)、铕弱负异常(δEu=0.72~0.97),相对富集Rb、Ba、Th、U、K 等,亏损 Nb、Ta、P、Ti 等,具火山弧花岗岩的特征。岩体具有较均一的 Sr、Nd 同位素组成：(87Sr/86Sr)i=0.70677~0.70685,εSr(t)=40.10~41.21,(143Nd/144Nd)i=0.51190~0.51191,εNd(t)=-2.62~-2.30, tDM＝1.31~1.38 Ga。其锆石U-Pb年龄为(488.9±1.7)~(470.5±3.1) Ma。表明古仍格萨拉东岩体形成于早奥陶世陆缘弧环境,可能是先存的中元古代幔源基性下地壳部分熔融的产物,其形成与古准噶尔洋向伊犁-中天山板块下的俯冲作用有关,标志着中天山北缘于早奥陶世时期已进入与俯冲消减有关的活动陆缘演化阶段。此次岩浆活动导致区内发生斑岩型铜矿化。
古倫溝地區古仍格薩拉東花崗閃長斑巖體位于中天山構造帶北緣。地毬化學和鋯石 U-P 年齡測定結果顯示：巖石高堿富 Na、貧 Fe 和 Mg、弱過鋁質(ACNK=0.98~1.11),稀土總量較低(∑REE=61.28×10-6~99.50×10-6)且分異明顯(LaN/YbN=7.82~22.80)、銪弱負異常(δEu=0.72~0.97),相對富集Rb、Ba、Th、U、K 等,虧損 Nb、Ta、P、Ti 等,具火山弧花崗巖的特徵。巖體具有較均一的 Sr、Nd 同位素組成：(87Sr/86Sr)i=0.70677~0.70685,εSr(t)=40.10~41.21,(143Nd/144Nd)i=0.51190~0.51191,εNd(t)=-2.62~-2.30, tDM＝1.31~1.38 Ga。其鋯石U-Pb年齡為(488.9±1.7)~(470.5±3.1) Ma。錶明古仍格薩拉東巖體形成于早奧陶世陸緣弧環境,可能是先存的中元古代幔源基性下地殼部分鎔融的產物,其形成與古準噶爾洋嚮伊犛-中天山闆塊下的俯遲作用有關,標誌著中天山北緣于早奧陶世時期已進入與俯遲消減有關的活動陸緣縯化階段。此次巖漿活動導緻區內髮生斑巖型銅礦化。
고륜구지구고잉격살랍동화강섬장반암체위우중천산구조대북연。지구화학화고석 U-P 년령측정결과현시：암석고감부 Na、빈 Fe 화 Mg、약과려질(ACNK=0.98~1.11),희토총량교저(∑REE=61.28×10-6~99.50×10-6)차분이명현(LaN/YbN=7.82~22.80)、유약부이상(δEu=0.72~0.97),상대부집Rb、Ba、Th、U、K 등,우손 Nb、Ta、P、Ti 등,구화산호화강암적특정。암체구유교균일적 Sr、Nd 동위소조성：(87Sr/86Sr)i=0.70677~0.70685,εSr(t)=40.10~41.21,(143Nd/144Nd)i=0.51190~0.51191,εNd(t)=-2.62~-2.30, tDM＝1.31~1.38 Ga。기고석U-Pb년령위(488.9±1.7)~(470.5±3.1) Ma。표명고잉격살랍동암체형성우조오도세륙연호배경,가능시선존적중원고대만원기성하지각부분용융적산물,기형성여고준갈이양향이리-중천산판괴하적부충작용유관,표지착중천산북연우조오도세시기이진입여부충소감유관적활동륙연연화계단。차차암장활동도치구내발생반암형동광화。
The East Gurenggesala granitic intrusion in Gulungou area on the northern margin of Middle Tianshan Mountains consist of granodiorite-porphyry with porphyry copper mineralization. The intrusion is characterized by enrichment of alkali, with Na2O/K2O ratio changing from 1.95 to 19.00, and depletion of Fe and Mg, accompanied by sub-alkaline (mainly tholeiitic and calc-alkaline series) and weakly peraluminous features (A/CNK=0.98~1.11). REE concentrations are low (∑REE=61.28×10-6~99.50×10-6) and show obvious differentiation between LREE and HREE (LaN/YbN=7.82~22.80), with weak Eu negative anomalies (δEu=0.72~0.97). In addition, the rock mass is relatively rich in such elements as Rb, Ba, Th, U and K, and poor in Nb, Ta, P, Ti etc., suggesting characteristics of volcanic-arc granite (VAG). Zircon LA-ICP-MS U-Pb dating results show that the crystallization of the intrusion took place from (488.9±1.7) Ma to (470.5±3.1) Ma, i.e., in Early Ordovician. Sr-Nd isotopic compositions of East Gurenggesala granitic intrusion are fairly uniform: (87Sr/86Sr)i=0.70677~0.70685,εSr(t)=40.10~41.21, (143Nd/144Nd)i=0.51190~0.51191, εNd(t)=-2.62 ~ -2.30, tDM=1.31~1.38 Ga, implying that magma originated from partial melting of Meso-Proterozoic mantle-derived basic lower crust. Based on both previous and present research results, the authors have reached the conslusion that East Gurenggesala granitic intrusion was formed in the epicontinental arc relevant to the subduction of the paleo-Junggar ocean towards Yili-Central Tianshan plate in Early Ordovician together with porphyry copper mineralization. In general, the emplacement of East Gurenggesala granitic intrusion marked the epoch when the northern margin of Middle Tianshan entered into the stage of active epicontinental arc in connection with subduction in Early Ordovician.
