發(fā)布時(shí)間：2018-12-16 18:10

【摘要】：義敦島弧形成于晚三疊世大規(guī)模俯沖造山作用過(guò)程中,位于松潘-甘孜褶皺帶和羌塘地體之間。稻城巖體和海子山巖體分別為義敦島弧上出露的晚三疊世和白堊紀(jì)花崗質(zhì)巖體。結(jié)合野外考察,本文對(duì)上述巖體進(jìn)行巖相學(xué)、鋯石U-Pb年代學(xué)和Hf同位素的研究,結(jié)果表明,1稻城巖體和海子山巖體主要礦物為斜長(zhǎng)石、鉀長(zhǎng)石、石英和黑云母,副礦物為鋯石、榍石、磁鐵礦和磷灰石等;鈉質(zhì)斜長(zhǎng)石顆粒,以及鉀長(zhǎng)石和石英不連續(xù)出現(xiàn),表明二者均屬于低熔線花崗巖,是含水條件下,在與造山事件有關(guān)的環(huán)境中形成。2稻城巖體的侵位年齡為217.4Ma,屬晚三疊世花崗巖侵入體,εHf(t)為-7.1~-0.1,二階段模式年齡(tDM2)為1.26~1.7Ga,表明在中元古代與揚(yáng)子克拉通經(jīng)歷了共同的地殼演化歷史;海子山巖體的形成時(shí)代為98.3 Ma,為白堊紀(jì)時(shí)期產(chǎn)物,εHf(t)變化于-12.1~+2.5,二階段模式年齡(tDM2)變化于1.0~1.93Ga。3結(jié)合前人研究成果,本文認(rèn)為稻城巖體源巖可能是與揚(yáng)子克拉通有關(guān)的中元古代的下地殼物質(zhì),在甘孜-理塘洋俯沖閉合后的同碰撞造山階段,因地幔巖漿底侵作用而發(fā)生了部分熔融,同時(shí)伴有少量的虧損地幔成分加入,之后上升侵位于中—上地殼,并且侵位后經(jīng)歷了快速的冷卻過(guò)程。海子山巖體是與俯沖有關(guān)的造山后伸展環(huán)境下形成的A2型花崗巖,源巖主要為中元古代地殼物質(zhì),同樣有少量地幔物質(zhì)加入,在白堊紀(jì)時(shí)侵位于地殼較淺部位,之后亦同樣經(jīng)歷了快速的冷卻過(guò)程。
[Abstract]:The Yidun island arc was formed during the late Triassic large-scale subduction orogeny between the Songpan-Ganzi fold belt and the Qiangtang terrane. The Daocheng and Haizishan intrusions are late Triassic and Cretaceous granitic rocks respectively. Combined with field investigation, the authors have studied the lithofacies, zircon U-Pb chronology and Hf isotopes of the abovementioned rocks. The results show that the main minerals of the Daocheng and Haizishan pluton are plagioclase, potash feldspar, quartz and biotite, and the main minerals are plagioclase, potassium feldspar, quartz and biotite. The accessory minerals are zircon sphene magnetite and apatite etc. The occurrence of sodium plagioclase particles, as well as potassium feldspar and quartz discontinuities, indicate that both of them belong to low-melting-line granites and are formed in an environment related to orogenic events under water-bearing conditions. 2 the emplacement age of the Daocheng rock body is 217.4 Ma. It belongs to the late Triassic granite intrusion, 蔚 Hf (t) is -7.1 ~ (-1) -0.1, and the two-stage model age (tDM2) is 1.26 ~ 1.7Ga, which indicates that the Mesoproterozoic and Yangtze craton experienced a common history of crustal evolution. The age of formation of the Haizi mountain body is 98.3 Ma, which is the product of Cretaceous period, 蔚 Hf (t) changes from -12.1-2.5, and the two-stage model age (tDM2) changes with 1.0~1.93Ga.3 combined with previous research results. In this paper, it is suggested that the source rocks of the Daocheng rock body may be the lower crust material of the Mesoproterozoic associated with the Yangtze craton. During the syncollision orogenic stage after the subduction of the Ganzi-Litang Ocean, partial melting occurred due to the mantle magmatic underthrust. At the same time, it is accompanied by a small amount of depleted mantle composition, and then rises and transgressions are located in the mid-upper crust and undergo a rapid cooling process after emplacement. The Haizishan rock body is an A2 type granite formed in the post-orogenic extensional environment related to subduction. The source rocks are mainly of the Mesoproterozoic crustal material, with a small amount of mantle material added, and transgression in the shallow part of the crust during the Cretaceous period. Also experienced the same rapid cooling process.
【作者單位】： 中國(guó)地質(zhì)科學(xué)院地質(zhì)研究所中國(guó)地質(zhì)調(diào)查局大陸動(dòng)力學(xué)研究中心;中國(guó)地質(zhì)大學(xué)地球科學(xué)學(xué)院地質(zhì)過(guò)程與礦產(chǎn)資源國(guó)家重點(diǎn)實(shí)驗(yàn)室;中國(guó)地質(zhì)科學(xué)院礦產(chǎn)資源研究所國(guó)土資源部成礦作用與資源評(píng)價(jià)重點(diǎn)實(shí)驗(yàn)室;
【基金】：中國(guó)地質(zhì)調(diào)查局項(xiàng)目(編號(hào)12120114061701、121201102000150005-06和12120115027001)聯(lián)合資助成果
【分類號(hào)】：P597.3;P588.121

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