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对来自苏北盆地盘石山、练山和方山地区新生代玄武岩中的50个橄榄岩包体矿物进行了系统的微区傅立叶变换红外光谱(Micro-FTIR)分析.结果显示,所有的单斜辉石和斜方辉石颗粒都含有以OH形式存在的结构水,盘石山、练山和方山橄榄岩的单斜辉石水含量分别为64×10-6～183×10-6、37×10-6～102×10-6和41×10-6～177×10-6;斜方辉石水含量分别为16×10-6～61×10-6、13×10-6～45×10-6和21×10-6～74×10-6.几乎所有的橄榄石都没有检测到明显的OH吸收峰,暗示其水含量低于仪器的检出限(～2×10-6).根据矿物水含量(假设橄榄石的水含量为2×10-6)和它们的体积分数计算的盘石山、练山和方山橄榄岩全岩的水含量分别为12×10-6～52×10-6、7×10-6～25×10-6和13×10-6～44×10-6.结合已经发表的橄榄岩包体的数据来看,在岩石圈地幔的物理化学条件下,单斜辉石与斜方辉石之间水的平衡分配系数大约为2.2±0.4.结合已经发表的安徽女山和河北汉诺坝的橄榄岩数据,对比世界上其他地区橄榄岩的数据来看,华北的岩石圈地幔具有低的水含量:华北橄榄岩的单斜辉石水含量多<200×10-6,而世界上其他地区(包括南非克拉通、美国新墨西哥地区、美国Colorado高原、美国盆岭省地区、墨西哥南部、法国中央地体以及加拿大WestKettle地区)橄榄岩的单斜辉石水含量多>200×10-6;华北的斜方辉石水含量多<100×10-6,而世界上其他地区多>100×10-6;华北的橄榄岩全岩水含量多<50×10-6,而世界上其他地区多>100×10-6.华北岩石圈地幔的低水含量有可能是由于上升软流圈的热侵蚀造成的,因此目前的华北岩石圈地幔可能大部分都是中生代岩石圈减薄后的残余,而不是新生地幔.
Fifty peridotitic enclaves in the Cenozoic basalts from the Panshan, Lianjianshan and Fangshan areas, Northern Jiangsu Province, were systematically analyzed by micro-Fourier transform infrared spectroscopy (Micro-FTIR). The results showed that all monoclinic Both pyroxene and orthopyroxene contain structural water in the form of OH. The water content of clinopyroxene in the Panshishan, Lianshan and Fangshan peridotites are 64 × 10-6 ~ 183 × 10-6, 37 × 10-6 ~ 102 × 10-6 and 41 × 10-6 ~ 177 × 10-6 respectively; the orthopyroxene water content is 16 × 10-6 ~ 61 × 10-6, 13 × 10-6 ~ 45 × 10-6 and 21 × 10-6 ~ 74 × 10-6 Almost all olivine did not detect obvious OH absorption peaks, suggesting that the water content is below the detection limit of the instrument (~ 2 × 10-6) The water content of the whole rock in Panshilian, Lianjianshan and Fangshan peridotite calculated from the mineral water content (assuming the water content of olivine is 2 × 10-6) and their volume fractions are 12 × 10-6 ~ 52 × 10-6, 7 × 10-6 ~ 25 × 10-6 and 13 × 10-6 ~ 44 × 10-6. According to the published data of peridotite inclusions, the physicochemical conditions of lithospheric mantle , The equilibrium partition coefficient of water between clinopyroxene and orthopyroxene is about 2.2 0.4. Comparing published peridotites data from Nvyeong Mountain and Hannoba Dam in Hebei Province, comparing the data of peridotites in other parts of the world, the lithospheric mantle in North China has low water content: clinopyroxene The water content is more than 200 × 10-6, while in the rest of the world, including the South African craton, the New Mexico region of the United States, the Colorado plateau of the United States, the Pelouring region of the United States, the southern Mexico, the central French terrain and the WestKettle region of Canada) The clinopyroxene water content is more than 200 × 10-6; the orthopyroxene water content in North China is more than 100 × 10-6, while the rest of the world is more than 100 × 10-6; the total rock water content in the North China peridotite More than 50 × 10-6, while the rest of the world is more than 100 × 10-6. The low water content of the North China lithospheric mantle may be due to the thermal erosion of the rising asthenosphere. Therefore, the current North China lithospheric mantle Mostly probably the remnants of Mesozoic lithosphere thinning, rather than the newborn mantle.