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本研究共涉及来自太行山和郯庐断裂岩浆带的12组基性岩墙群,岩墙群具体出露于河北省、山西省、山东省和安徽省。研究中给出了新的锆石LA-ICP-MS U-Pb年龄、地球化学和Sr-Nd-Pb同位素基性岩墙测试数据。基性岩墙形成于128.1±1.2Ma与115.0±0.8Ma之间,且具有典型的辉绿结构。另外,基性岩墙富集轻稀土元素(LREE)、个别大离子亲石元素(如,Rb、Ba、Sr)、Pb和Th,亏损Nb、Ta和Ti,具有高的初始87Sr/86Sr比值(0.7056~0.7105),负的εNd(t)(-15.5~-12.4)、相对一致的初始Pb同位素比值(206Pb/204Pb=16.45~16.49、207Pb/204Pb=15.44~15.51、208Pb/204Pb=36.49~36.53)及较大的Nd模式年龄(tNd DM2=1.82~2.69Ga)。研究结果表明,基性岩墙来自石榴石二辉橄榄岩地幔源区(类似EM1)一定程度的(1.0%~5.0%)部分熔融,岩浆侵位前经历了橄榄石、单斜辉石和角闪石的分离结晶作用,同时受到少量地壳混染的影响。目前,关于华北克拉通破坏和中生代岩浆作用的成因已有较多可能模式,本研究基性岩墙成因的新模式:古太平洋板块与华北克拉通的持续碰撞,导致华北克拉通岩石圈(地幔和地壳)加厚,并发生可能的榴辉岩化,并在一定时间发生拆沉作用。在新模式的制约下,导致了研究区中生代基性岩墙的产生和侵位。
In this study, a total of 12 groups of basic dykes from the magmatic belt of the Taihang and Tanlu faults are involved. The dykes are exposed in Hebei Province, Shanxi Province, Shandong Province and Anhui Province. The new zircon LA-ICP-MS U-Pb age, geochemistry and Sr-Nd-Pb isotopic dikes data are presented. The basic dykes are formed between 128.1 ± 1.2Ma and 115.0 ± 0.8Ma, and have a typical greenery structure. In addition, the mafic dykes are enriched in LREE, individual large lithophile elements (eg, Rb, Ba, Sr), Pb and Th, and depleted in Nb, Ta and Ti with high initial 87Sr / 86Sr ratios (0.7056 ~ 0.7105), negative εNd (t) (-15.5 ~ -12.4) and relatively consistent initial Pb isotope ratio (206Pb / 204Pb = 16.45 ~ 16.49,207Pb / 204Pb = 15.44 ~ 15.51,208Pb / 204Pb = 36.49 ~ 36.53) and the larger Nd model age (tNd DM2 = 1.82-2.66 Ga). The results show that the basic dykes are partially melted from a certain degree (1.0% -5.0%) of the mantle source area of garnet-type lherzolites (similar to EM1), and have undergone olivine, clinopyroxene and amphibole before emplacement Separation of crystallization, while being affected by a small amount of crustal contamination. At present, there are many possible models of the origin of the North China craton and Mesozoic magmatism. A new model of the genesis of the basic dyke: the continuous collision of the Paleo-Pacific plate with the North China Craton led to the collision of the North China craton lithosphere And the crust) thickening, and possible eclogite, and delamination occurred at a certain time. Under the constraints of the new model, the generation and emplacement of Mesozoic mafic dykes in the study area have been caused.