本文選題：Sr-Nd-Hf同位素 + 埃達(dá)克質(zhì)巖��； 參考：《中國科學(xué):地球科學(xué)》2017年07期

【摘要】：位于大陸內(nèi)部的埃達(dá)克質(zhì)巖通常來自于加厚下地殼或拆沉下地殼的部分熔融,對(duì)這類巖石的研究可以為我們了解地殼演化過程提供重要的信息.本文對(duì)產(chǎn)于華夏地塊腹地的具有埃達(dá)克質(zhì)巖特征的靈溪花崗閃長巖開展了詳盡的研究工作.LA-ICP-MS鋯石U-Pb年代學(xué)的結(jié)果顯示其形成于早白堊世晚期((100±1)Ma).靈溪巖體的地球化學(xué)特征,如高SiO_2含量(大部分樣品在64.4~68.9wt.%)和Sr含量(624~894ppm)、高的Sr/Y比值(49.9~60.8)和La/Yb比值(23.4~42.8),以及低Y含量(10.3~17.1ppm)、Ni含量(5.62~11.8)和MgO含量(絕大多數(shù)樣品在0.86~1.57wt.%),表明其來自于下地殼物質(zhì)的部分熔融.靈溪巖體的87Sr/86Sr初始比值為0.7086~0.7091,ε_(tái)(Nd)(t)值為.6.2~.5.9,而鋯石的ε_(tái)(Hf)(t)值則主要變化于.10.1~.7.6.地球化學(xué)模擬的結(jié)果顯示靈溪花崗閃長巖是由元古代地殼物質(zhì)在至少40km的地殼深度下(或壓力≥1.2kbar)部分熔融形成的,部分熔融的殘留相為含石榴子石角閃巖相.結(jié)合前人對(duì)華夏地塊構(gòu)造演化進(jìn)程的研究成果,本文認(rèn)為華夏地塊的地殼在早白堊世晚期的一次擠壓事件中發(fā)生了一定程度的加厚,使地殼厚度達(dá)到至少40km,這與華夏地塊內(nèi)存在上白堊統(tǒng)紅色礫巖角度不整合于下白堊統(tǒng)或侏羅系巖層之上的地質(zhì)觀察相吻合.在這次擠壓事件之后,華夏地塊受到古太平洋板塊高角度俯沖的影響,進(jìn)入巖石圈伸展減薄的構(gòu)造環(huán)境.隨著巖石圈的減薄,華夏地塊的下地殼物質(zhì)受到上涌的軟流圈物質(zhì)的加熱并發(fā)生部分熔融,進(jìn)而產(chǎn)生了靈溪花崗閃長巖以及其他同時(shí)代的花崗巖類.本文的研究為了解華夏地塊早白堊世的地殼演化提供了新的信息.
[Abstract]:The adakite located in the interior of the continent usually comes from the partial melting of the thickened or desunk lower crust. The study of these rocks can provide important information for us to understand the evolution process of the crust. In this paper, a detailed study of Lingxi granodiorite with the characteristics of adakitic rocks in the hinterland of the Huaxia massif has been carried out. The results of U-Pb geochronology of zircon from LA-ICP-MS indicate that it was formed in the late early Cretaceous period. Geochemical characteristics of Lingxi rock mass, For example, high SiO_2 content (most samples are at 64.4 ~ 68.9 wt.), Sr content of 624894 ppm-1, high Sr/Y ratio of 49.9% ~ 60.8% and La/Yb ratio of 23.4 ~ 42.8%, as well as a low Y content of 10.3 ~ 17.1 ppm-1, Ni content of 5.6211.8) and MgO content (the vast majority of the samples are at 0.86 ~ 1.57 wt.), indicating that they originated from partial melting of the lower crust material. The initial 87Sr/86Sr ratio of Lingxi rock mass is 0.7086 / 0.7091, and the value of 蔚 _ S _ D _ (+) _ (t) is .6.2 ~ 5.9. while the value of zircon's 蔚 ~ (-1) is mainly changed from .10.1 ~ (?) ~ 7.6. The geochemical simulation results show that the Lingxi granodiorite was formed by partial melting of the Proterozoic crustal material at the crustal depth of at least 40km (or pressure 鈮，

本文編號(hào)：1932978