地质学报
地質學報
지질학보
ACTA GEOLOGICA SINICA
2014年
2期
167-184
,共18页
李双应%杨栋栋%王松%万秋%王道轩
李雙應%楊棟棟%王鬆%萬鞦%王道軒
리쌍응%양동동%왕송%만추%왕도헌
碎屑岩成分%碎屑锆石年代学%物源分析%构造演化%上石炭统%南天山
碎屑巖成分%碎屑鋯石年代學%物源分析%構造縯化%上石炭統%南天山
쇄설암성분%쇄설고석년대학%물원분석%구조연화%상석탄통%남천산
composition of clastic rocks%chronology of detrital zircon%provenance%tectonic evolution%Upper Carboniferous%South Tianshan
晚古生代是天山构造带发生变革的关键时期，对南天山层序清楚尚未变质的晚古生代沉积记录进行研究，对于恢复南天山晚古生代的构造古地理、并对其构造演化史提供约束，具有重要地质意义。南天山中段上石炭统阿依里河组砂岩主要为含砾砂岩、岩屑砂岩、次岩屑砂岩、长石砂岩和含铁岩屑砂岩，砂岩中石英颗粒含量67．41％，岩屑25．07％，长石7．52％，Q/（F＋L）平均为2．07，岩石具有低的结构成熟度和成分成熟度。碎屑岩SiO2平均为64．78％，Al2O310．22％，TiO20．35％，TFe2O34．23％，MgO 1．37％，CaO 7．16％，K2O 2．13％，Na2O 0．93％。稀土总量∑REE 平均为130．1×10-6，δEu 异常0．74，LaN/YbN 9．4。砂岩中重矿物组合主要为锆石、白钛石、赤褐铁矿和黄铁矿，其次有电气石、磷灰石、金红石、石榴子石、铬铁矿和锐钛矿。阿依里河组的源岩主要为中-酸性火成岩、低级-中级变质岩和沉积岩，还有少量基性岩等。根据 QFL 判别，砂岩物源区主要为消减杂岩源区，其次是弧造山带和碰撞造山带源区。根据稀土元素、微量元素特征，以及 Th-Co-Zr/10、Th-Sc-Zr/10和Ti/Zr-La/Sc判别图，阿依里河组碎屑岩物源区属于大陆岛弧区和活动大陆边缘区，与上地壳源区相比，有铁镁质的叠加。校正后的碎屑岩化学风化指数CIAcorr．平均为71．25（52．25～89．40），指示源区主要经历了中等程度的化学风化。砂岩碎屑LA-ICP-Ms锆石U-Pb年龄测定表明，锆石年龄分为两期，主要为404～542 Ma，其次是1797～2436 Ma，表明物源区地质体时代主要为早古生代和古元古代，它们和南天山早古生代消减带弧和塔里木北缘库鲁克塔格古元古代基底比较吻合。同时，进一步将南天山造山带开始碰撞的时间限制在早泥盆世末-中泥盆世，俯冲汇聚在早古生代，大规模的隆升剥露在二叠纪以后。
晚古生代是天山構造帶髮生變革的關鍵時期，對南天山層序清楚尚未變質的晚古生代沉積記錄進行研究，對于恢複南天山晚古生代的構造古地理、併對其構造縯化史提供約束，具有重要地質意義。南天山中段上石炭統阿依裏河組砂巖主要為含礫砂巖、巖屑砂巖、次巖屑砂巖、長石砂巖和含鐵巖屑砂巖，砂巖中石英顆粒含量67．41％，巖屑25．07％，長石7．52％，Q/（F＋L）平均為2．07，巖石具有低的結構成熟度和成分成熟度。碎屑巖SiO2平均為64．78％，Al2O310．22％，TiO20．35％，TFe2O34．23％，MgO 1．37％，CaO 7．16％，K2O 2．13％，Na2O 0．93％。稀土總量∑REE 平均為130．1×10-6，δEu 異常0．74，LaN/YbN 9．4。砂巖中重礦物組閤主要為鋯石、白鈦石、赤褐鐵礦和黃鐵礦，其次有電氣石、燐灰石、金紅石、石榴子石、鉻鐵礦和銳鈦礦。阿依裏河組的源巖主要為中-痠性火成巖、低級-中級變質巖和沉積巖，還有少量基性巖等。根據 QFL 判彆，砂巖物源區主要為消減雜巖源區，其次是弧造山帶和踫撞造山帶源區。根據稀土元素、微量元素特徵，以及 Th-Co-Zr/10、Th-Sc-Zr/10和Ti/Zr-La/Sc判彆圖，阿依裏河組碎屑巖物源區屬于大陸島弧區和活動大陸邊緣區，與上地殼源區相比，有鐵鎂質的疊加。校正後的碎屑巖化學風化指數CIAcorr．平均為71．25（52．25～89．40），指示源區主要經歷瞭中等程度的化學風化。砂巖碎屑LA-ICP-Ms鋯石U-Pb年齡測定錶明，鋯石年齡分為兩期，主要為404～542 Ma，其次是1797～2436 Ma，錶明物源區地質體時代主要為早古生代和古元古代，它們和南天山早古生代消減帶弧和塔裏木北緣庫魯剋塔格古元古代基底比較吻閤。同時，進一步將南天山造山帶開始踫撞的時間限製在早泥盆世末-中泥盆世，俯遲彙聚在早古生代，大規模的隆升剝露在二疊紀以後。
만고생대시천산구조대발생변혁적관건시기，대남천산층서청초상미변질적만고생대침적기록진행연구，대우회복남천산만고생대적구조고지리、병대기구조연화사제공약속，구유중요지질의의。남천산중단상석탄통아의리하조사암주요위함력사암、암설사암、차암설사암、장석사암화함철암설사암，사암중석영과립함량67．41％，암설25．07％，장석7．52％，Q/（F＋L）평균위2．07，암석구유저적결구성숙도화성분성숙도。쇄설암SiO2평균위64．78％，Al2O310．22％，TiO20．35％，TFe2O34．23％，MgO 1．37％，CaO 7．16％，K2O 2．13％，Na2O 0．93％。희토총량∑REE 평균위130．1×10-6，δEu 이상0．74，LaN/YbN 9．4。사암중중광물조합주요위고석、백태석、적갈철광화황철광，기차유전기석、린회석、금홍석、석류자석、락철광화예태광。아의리하조적원암주요위중-산성화성암、저급-중급변질암화침적암，환유소량기성암등。근거 QFL 판별，사암물원구주요위소감잡암원구，기차시호조산대화팽당조산대원구。근거희토원소、미량원소특정，이급 Th-Co-Zr/10、Th-Sc-Zr/10화Ti/Zr-La/Sc판별도，아의리하조쇄설암물원구속우대륙도호구화활동대륙변연구，여상지각원구상비，유철미질적첩가。교정후적쇄설암화학풍화지수CIAcorr．평균위71．25（52．25～89．40），지시원구주요경력료중등정도적화학풍화。사암쇄설LA-ICP-Ms고석U-Pb년령측정표명，고석년령분위량기，주요위404～542 Ma，기차시1797～2436 Ma，표명물원구지질체시대주요위조고생대화고원고대，타문화남천산조고생대소감대호화탑리목북연고로극탑격고원고대기저비교문합。동시，진일보장남천산조산대개시팽당적시간한제재조니분세말-중니분세，부충회취재조고생대，대규모적륭승박로재이첩기이후。
We can restore Late Paleozoic paleogeography and reveal tectonic evolution history of South Tianshan, based on the study of Carboniferous sedimentary records,when was in Late Paleozoic that Tianshan tectonic zone happened to great changes.The sandstones of Upper Carboniferous Ayilihe Formation in the middle segment of South Tianshan are mostly composed of pebbly sandstone,litharenite,sublitharenite, arkose and ferruginous sandstone.The component of the sandstones includes mostly quartz 67.41%,next lithic fragment 21.8%,and a little feldspar 7.52%.The sandstones have average of 2.07 for Q/F+L,and low textural and compositional maturity.The detrital rocks have average contents of SiO2 64.78%,Al2 O3 10.22%,TiO2 0.35%,TFe2O3 4.23%,MgO 1.37%,CaO 7.16%,K2O 2.13%,Na2O 0.93%,and average 130.1×10-6 of ∑REE,0.7 ofδEu and 9.4 of LaN/YbN.Heavy mineral assemblage of the sandstones includes mostly zircon,leucoxene,limonite and pyrite,next tourmaline,apatite,rutile,garnet,chromite and anatase.The source rocks of the Ayilihe Formation are mostly composed of acidic igneous rock,lower-medium metamorphism rocks and sedimentary rocks,and a little basic rock.The provenance of the sandstones had tectonic settings of mostly subduction complex,next arc orogen and collision orogen,based on the QFL discriminant diagrams.According to the REE,trace elements,and Th-Co-Zr/10,Th-Sc-Zr/10,Ti/Zr-La/Sc discriminant diagrams,the provenance of detrital rocks had the tectonic settings of continental island arc and active continental margin,and with some femic constituents compared with the source region of the upper crust.The chemical index of alteration corrected (CIAcorr.)of the detrital rocks has an average of 71.25 (52.25~89.40),which indicates that provenance had mostly gone moderate chemical weathering.According to the U-Pb ages of LA-ICP-MS of 79 detrital zircon grains,the source rocks of Upper Carboniferous detrital rocks came from terrains with two different geological times,most 404~542 Ma,second 1797~2436 Ma,which indicates that source rocks came mostly from Early Paleozoic and paleo-Proterozoic.They are equivalent to magma arc of Early Paleozoic subduction zone in the northern of South Tianshan,and southeastern Proterozoic basement of Kulukedage in the northern of Tarim.Hence,it also indicates that the collision time of South Tianshan Orogen may be limited in the end of Early Devonian to Middle Devonian,subduction and converge happened during Early Paleozoic,and large-scale uplifting and exhumation happened after Permian.
