本文選題：遼南地塊　切入點(diǎn)：太古宙　出處：《巖石學(xué)報(bào)》2017年09期 　論文類型：期刊論文

【摘要】：膠-遼-吉活動(dòng)/造山帶是華北克拉通早前寒武紀(jì)基底三條古元古代構(gòu)造帶之一,對(duì)其鄰區(qū)內(nèi)太古宙地質(zhì)體的巖石組合和時(shí)空分布的研究,可為制約膠-遼-吉帶的構(gòu)造屬性以及華北克拉通東部在古元古代時(shí)期的構(gòu)造格局提供重要依據(jù)。膠-遼-吉帶的北側(cè)為龍崗地塊,南側(cè)為遼南和狼林地塊,本文對(duì)遼南地塊中典型前寒武紀(jì)基底變質(zhì)巖石進(jìn)行了詳細(xì)的野外地質(zhì)、巖石學(xué)和鋯石LA-ICP-MS U-Pb年代學(xué)研究,結(jié)果顯示原巖為石英閃長(zhǎng)巖或英云閃長(zhǎng)巖的黑云角閃片麻巖(DL05-1)和侵入其中的花崗質(zhì)脈體(DL05-2)分別形成于2523±11Ma(MSWD=0.62)和2505±13Ma(MSWD=0.67),原巖為TTG巖系的黑云斜長(zhǎng)片麻巖(DL10-1)形成于2521±12Ma(MSWD=1.15)。2件斜長(zhǎng)角閃巖樣品(DL12-1和DL07-1)分別給出2521±16Ma(MSWD=1.9)和2464±20Ma(MSWD=0.72)的~(207)Pb/~(206)Pb加權(quán)平均年齡,前者的鋯石形態(tài)、結(jié)構(gòu)和Th-U體系組成具有高溫巖漿成因的特征,因此2521±16Ma代表基性原巖的形成時(shí)代,后者的鋯石沒有明顯的內(nèi)部結(jié)構(gòu),且Th、U含量低(分別為6×10~(-6)~29×10~(-6)、9×10~(-6)~26×10~(-6))具變質(zhì)重結(jié)晶鋯石的特征,2464±20Ma代表區(qū)域變質(zhì)事件的年齡。侵入斜長(zhǎng)角閃巖的2件花崗片麻巖樣品(DL12-2和DL07-2)207Pb/206Pb加權(quán)平均年齡分別為2498±18Ma(MSWD=1.4)和2.1Ga,1件鉀質(zhì)花崗巖樣品(DL17-1)由于強(qiáng)烈的Pb丟失未能獲得準(zhǔn)確的形成年齡,根據(jù)野外產(chǎn)狀和鋯石U-Th-Pb組成推測(cè)該鉀質(zhì)花崗巖形成于新太古代晚期。雖然遼南地塊內(nèi)太古宙表殼巖的時(shí)空分布規(guī)律目前還不清楚,但本文的研究結(jié)果進(jìn)一步確認(rèn),遼南地塊內(nèi)存在新太古代2.52Ga基性巖、閃長(zhǎng)巖和TTG組合,它們的形成時(shí)代總體上不晚于共生的花崗巖(2.50Ga),而后遼南地塊經(jīng)歷了新太古代晚期2.46Ga區(qū)域變質(zhì)作用的改造。侵位時(shí)代接近2.1Ga花崗巖的存在表明遼南地塊太古宙陸殼在形成后受到2.1Ga構(gòu)造-熱事件的影響。另一方面,本文研究的花崗質(zhì)巖石樣品中殘余鋯石核年齡分布于2.61~2.51Ga,表明遼南地塊內(nèi)古老大陸地殼物質(zhì)的形成時(shí)代至少可以追溯至新太古代早期。遼南地塊內(nèi)太古宙巖漿、變質(zhì)作用時(shí)限和陸殼物質(zhì)的形成時(shí)間都與華北克拉通東部可以對(duì)比,具有華北的太古宙基底屬性。與狼林地塊相比,遼南地塊內(nèi)太古宙的巖石類型更加豐富,規(guī)模也更大;與膠-遼-吉活動(dòng)/造山帶北側(cè)龍崗地塊相比,遼南地塊內(nèi)尚沒有發(fā)現(xiàn)大規(guī)模條帶狀鐵建造(BIF)和形成于新太古代之前(2.8Ga)的巖石,且變質(zhì)程度相對(duì)較低。目前的地質(zhì)和年代學(xué)證據(jù)尚不支持遼南地塊與膠-遼-吉帶北側(cè)的龍崗地塊原屬于同一陸殼基底。
[Abstract]:The Jiao-Liaoji active / orogenic belt is one of the three ancient Gu Yuan tectonic belts in the early Precambrian basement of the North China Craton. The rock assemblages and temporal and spatial distribution of the Archean geological bodies in the adjacent area are studied. It can provide an important basis for restricting the tectonic properties of the Jiao-Liaojia-Ji belt and the tectonic pattern of the eastern North China Craton in the Paleoproterozoic period. The north side of the Jiao-Liaojian-Ji belt is the Longgang block, and the south side is the southern Liaoning and Langlin blocks. In this paper, the typical Precambrian basement metamorphic rocks in the southern Liaoning block have been studied in detail in the field geology, petrology and zircon LA-ICP-MS U-Pb chronology. The results show that the quartz diorite or dolomite gneiss DL05-1) and the intrusive granitic vein DL05-2) were formed in 2523 鹵11 Ma-MSWD0.62) and 2505 鹵13Ma-MSWD0.67, respectively, and the TTG series of rubric gneiss DL10-1) was formed in 2521 鹵12MaMMSWD1.15.2 pieces of plagioclase. The results show that the diorite is composed of quartz diorite or quartz diorite (DL05-1) and the intrusive granitic vein (DL05-2) was formed at 2521 鹵12MaMMSWD1.15.2. For diorite samples DL12-1 and DL07-1), the weighted average age of 207Pb / L / 206U Pb for 2521 鹵16MaM MSWDU 1.9) and 2464 鹵20MaM MSWDU 0.72), respectively, is given. The zircon morphology, structure and Th-U system composition of the former have the characteristics of high-temperature magmatic genesis, so 2521 鹵16Ma represents the age of the formation of the basic protolith, while the zircon of the latter has no obvious internal structure. Moreover, the low content of Thu (29 脳 10 ~ (10)) (9 脳 10 ~ (10)) ~ (9) ~ (6) ~ (6) ~ (6) ~ (-) ~ (26 脳 10 ~ (10)) zircon is characteristic of metamorphic recrystallization zircon representing the age of regional metamorphism. Two granitic gneiss samples (DL12-2 and DL07-2)207Pb/206Pb weighted average age of 2498 鹵18MaMMSWD1.4) and 2.1 ~ (1) kalitic zircons intruding into amphibolite are characterized by metamorphic recrystallitic zircon age of 2464 鹵20Ma. The weighted mean ages of DL12-2 and DL07-2)207Pb/206Pb are 2498 鹵18MaMSWD1.4 and 2.1 ~ (-1), respectively. DL17-1) due to strong Pb loss, an accurate age of formation has not been obtained. According to the field occurrence and zircon U-Th-Pb composition, the potash granite was formed in the late NeoArchean. Although the temporal and spatial distribution of Archean epidermal rocks in the southern Liaoning massif is not clear, the results of this paper further confirm that, NeoArchean 2.52Ga basic rocks, diorite and TTG assemblages exist in the southern Liaoning massif. Their forming age was not later than that of the INTERGROWTH granite (2.50GaN) in general, and the southern Liaoning massif underwent the reformation of late NeoArchean 2.46Ga regional metamorphism. The presence of the emplacement age close to 2.1 Ga granite indicates the Archean continental crust of the southern Liaoning block. After formation, it was influenced by 2.1 Ga tectonic-thermal events. The age distribution of the residual zircon in the granitic samples studied in this paper is 2.61 ~ 2.51 Ga, which indicates that the formation of the ancient continental crustal material in the southern Liaoning block can be traced back to the early NeoArchean period at least, and the Archean magma in the southern Liaoning block. The time limit of metamorphism and the forming time of continental crust material can be compared with the eastern part of North China craton, which has the Archean basement attribute of North China. Compared with the Langlin block, the Archean rock types in southern Liaoning block are more abundant and the scale is larger. Compared with the Longgang massif on the north side of the Jiao-Liaojia-Jiagi active / orogenic belt, no large scale banded iron formation (BIFs) and rocks formed before the NeoArchean (2.8Ga) have been found in the southern Liaoning massif. The present geological and chronological evidence does not support that the southern Liaoning block and the Longgang block on the north side of the Jiao-Liaojia-Ji belt belong to the same continental crust basement.
【作者單位】： 中國(guó)地質(zhì)科學(xué)院地質(zhì)研究所;
【基金】：國(guó)家自然科學(xué)基金重點(diǎn)項(xiàng)目(41430210) 中國(guó)地質(zhì)調(diào)查局地質(zhì)大調(diào)查項(xiàng)目(DD20160121) 中國(guó)地質(zhì)科學(xué)院基礎(chǔ)科研業(yè)務(wù)費(fèi)(YYWF201703、J1714)聯(lián)合資助
【分類號(hào)】：P534.2;P542
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本文編號(hào)：1597669