本文選題：蓮花山巖體 + 鉀質(zhì)巖漿巖　； 參考：《巖石學(xué)報(bào)》2017年07期

【摘要】：沿金沙江-哀牢山古特提斯縫合帶兩側(cè)發(fā)育的巨型新生代陸內(nèi)鉀質(zhì)巖漿巖帶一直是地質(zhì)學(xué)界關(guān)注的熱點(diǎn),其西側(cè)的印支地塊鉀質(zhì)巖漿巖尚缺乏深入探討,制約著對(duì)鉀質(zhì)巖漿巖帶成因的理解以及對(duì)印支地塊深部殼幔物質(zhì)結(jié)構(gòu)的認(rèn)識(shí)。本研究選取的蓮花山巖體位于印支地塊北部的蘭坪盆地東南端,依次對(duì)其開展系統(tǒng)的巖相學(xué)、元素地球化學(xué)、鋯石U-Pb年代學(xué)以及Hf同位素研究。結(jié)果顯示,巖體主要由石英二長(zhǎng)斑巖組成,LA-ICPMS鋯石U-Pb定年結(jié)果制約巖體侵位時(shí)代在~34Ma。巖石樣品具有富堿(Na_2O+K_2O=9.0%~9.2%)、高K(K_2O/Na_2O=1.0~1.2)特征,屬鉀玄巖漿系列;富集Th和U等大離子親石元素,虧損Nb和Ta等高場(chǎng)強(qiáng)元素,輕稀土元素富集((La/Yb)N=22~24)。綜合反映蓮花山鉀質(zhì)巖漿巖系由大洋板片俯沖作用造成的富集源區(qū)的部分熔融作用而產(chǎn)生。鋯石εHf(t)在+1.4~+4.6,集中在+2.8~+4.0,對(duì)應(yīng)的Hf同位素地殼模式年齡為1027~815Ma,集中在934~860Ma。巖體集中的鋯石εHf(t)值和缺乏繼承鋯石的特征,說(shuō)明巖漿巖上侵過(guò)程中未受到圍巖的混染。目前已知的印支地塊東部自新元古代以來(lái)(1000Ma)經(jīng)歷的俯沖作用僅有金沙江-哀牢山古特提斯洋二疊紀(jì)(ca.290~250Ma)西向俯沖,蓮花山巖體鋯石具有的新元古代Hf同位素地殼模式年齡反映古特提斯洋板片俯沖過(guò)程有陸源沉積物質(zhì)加入地幔中,該認(rèn)識(shí)與巖石Nb/U比值(1.3~4.7)所反映的加入地幔的俯沖物質(zhì)屬性一致。蓮花山巖體和其西側(cè)同期卓潘鉀質(zhì)雜巖體與揚(yáng)子西緣鉀質(zhì)巖體群同屬金沙江-哀牢山鉀質(zhì)巖漿巖帶的組成部分,它們由始新世時(shí)期古特提斯縫合帶加厚巖石圈拆沉作用導(dǎo)致的軟流圈熱上涌而誘發(fā)。該構(gòu)造-熱事件影響的空間范圍可能較傳統(tǒng)認(rèn)為的更大,其向西遠(yuǎn)涉至印支地塊內(nèi)部,從而導(dǎo)致了蓮花山和卓潘等巖體的形成。
[Abstract]:The giant Cenozoic intracontinental potash magmatic belt developed along the sides of the Jinshajiang-Ailaoshan paleoTethys suture zone has always been a hot topic in the geological field, but the Indosinian block potash magma in the west side of the belt has not been thoroughly discussed. It restricts the understanding of the genesis of the potash magmatic belt and the material structure of the deep crust and mantle of the Indosinian block. The Lianhuashan rock body selected in this study is located at the southeast end of the Lanping basin in the northern part of the Indosinian block. The lithology, element geochemistry, zircon U-Pb chronology and HF isotopic studies have been carried out in turn. The results show that the rock mass is mainly composed of quartz monzonitic porphyry, and the results of U-Pb dating of zircon restrict the emplacement age of the intrusive body at 34 Ma. The rock samples have the characteristics of rich alkali-rich Na2OK2O-9.0 and 9.2, and high KKK _ 2O / Na _ 2O _ (1.0 ~ 1.2), which belong to the kaliacite magma series, and are rich in large ion lithophile elements such as Th and U, depleted in high field strength elements such as NB and Ta, and enriched in La-r-Yb / N _ (22) O _ (24) ~ (2 +). It is shown that the Lianhuashan potash magmatic series is caused by partial melting of the enriched source area caused by subduction of oceanic plate. The zircon 蔚 Hfct) ranges from 1.4 to 4.6, mainly in the range of 2.8 ~ 4.0, corresponding to the crustal model age of 1027 ~ 815 Ma and 934 ~ 860 Ma. The concentration of zircon 蔚 Hftand and the lack of inherited zircon indicate that the magmatic rocks are not mixed with each other during the intrusion. The known subduction in the eastern part of the Indosinian block since the Neoproterozoic is only the Jinsha River and Ailao PaleoTethys Permian Permian Permian with westward subduction. The age of neoproterozoic HF isotopic crustal model of zircon from Lianhuashan pluton reflects the subduction process of Paleotertes oceanic plate in which continental sedimentary material is added to the mantle. This understanding is consistent with the subduction properties of the mantle as reflected by the rock Nb/U ratio of 1.3 ~ 4.7. The Lianhuashan rock body and the Zhuopan potash complex in the western side of Lianhuashan rock body and the potash rock mass group in the western margin of Yangtze are both part of the Jinshajiang-Ailaoshan potash magmatic belt. They were induced by the thermal upwelling of the asthenosphere caused by the thickening lithosphere in the Paleocene suture zone during the Eocene. The influence of the tectonic-thermal event on the spatial range may be larger than the traditional thought, which extends westward to the interior of the Indosinian block, resulting in the formation of the Lianhuashan and Zhuopan rock bodies.
【作者單位】： 中國(guó)地質(zhì)大學(xué)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)院地質(zhì)力學(xué)研究所;云南省地質(zhì)礦產(chǎn)勘查院;
【基金】：國(guó)家重點(diǎn)基礎(chǔ)研究發(fā)展計(jì)劃“973”項(xiàng)目(2015CB452606、2009CB421008) 國(guó)家重點(diǎn)研發(fā)計(jì)劃(2016YFC0600307) 國(guó)家自然科學(xué)基金青年項(xiàng)目(41602090)聯(lián)合資助
【分類號(hào)】：P584;P597

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