苦橄岩和科马提岩都是富镁的超镁铁质火山岩，早先，学术界大多关注它们之间的相似性，而对于它们之间的差异性很少强调。于是认为二者的地球化学性质近似，成因类似，形成条件类似。本文采用全数据模式的研究方法，从数据库收集了全球...苦橄岩和科马提岩都是富镁的超镁铁质火山岩，早先，学术界大多关注它们之间的相似性，而对于它们之间的差异性很少强调。于是认为二者的地球化学性质近似，成因类似，形成条件类似。本文采用全数据模式的研究方法，从数据库收集了全球太古宙全部科马提岩和后太古宙全部苦橄岩数据，对比的结果表明，太古宙科马提岩与后太古宙苦橄岩完全不同，它们之间几乎没有可比性。科马提岩与苦橄岩，不仅地球化学特征不同，而且成因不同，形成条件不同，产出时代不同，源区组成也不同。这种不同，反映了太古宙和后太古宙不可能属于同样的构造体制。太古宙是火球时代，地球异常的热，主导的可能是静止盖幔构造（stagnant lid tectonics）；后太古宙是热球时代，地球相对冷了许多，主导的是板块构造（plate tectonics）。科马提岩在太古宙广泛出露，无需地幔柱模式；而苦橄岩在后太古宙很少出露，才真正需要地幔柱模式。展开更多
Six tektites from Guilin of Guangxi, Hainan, and Guangdong were analyzed for the abundances of major elements and 27 trace elements. All samples are splash-form tektites and have SiO2 contents ranging from 73.1wt% to ...Six tektites from Guilin of Guangxi, Hainan, and Guangdong were analyzed for the abundances of major elements and 27 trace elements. All samples are splash-form tektites and have SiO2 contents ranging from 73.1wt% to 76.0wt% (74.6wt% on average). The chemical compositions, except Cr and Ni, of tektites from different areas, are similar. Guangdong tektite shows enrichments of Ni and Cr contents by a factor of 3, and has slightly higher MgO and FeO than Hainan and Guilin tektites. It indicates that the tektites were formed by mixing several target rocks. The major and trace element concentrations of southern China tektites closely resemble previously reported data for average splash-form and Muong Nong-type indochinites, indicating that they have the same source. (La/Lu)CI (7.99), Zr/Hf (35.45 on average), Ba/Rb (3.59 on average), and the rare earth element (REE) contents of tektites are similar to those of typical post Archean upper crustal rocks. This study suggests that the best fit for the target source of southern China tektites could be a combination of 41% shale, 2% sandstone, 20% greywacke, and 37% quartzite.展开更多
文摘苦橄岩和科马提岩都是富镁的超镁铁质火山岩，早先，学术界大多关注它们之间的相似性，而对于它们之间的差异性很少强调。于是认为二者的地球化学性质近似，成因类似，形成条件类似。本文采用全数据模式的研究方法，从数据库收集了全球太古宙全部科马提岩和后太古宙全部苦橄岩数据，对比的结果表明，太古宙科马提岩与后太古宙苦橄岩完全不同，它们之间几乎没有可比性。科马提岩与苦橄岩，不仅地球化学特征不同，而且成因不同，形成条件不同，产出时代不同，源区组成也不同。这种不同，反映了太古宙和后太古宙不可能属于同样的构造体制。太古宙是火球时代，地球异常的热，主导的可能是静止盖幔构造（stagnant lid tectonics）；后太古宙是热球时代，地球相对冷了许多，主导的是板块构造（plate tectonics）。科马提岩在太古宙广泛出露，无需地幔柱模式；而苦橄岩在后太古宙很少出露，才真正需要地幔柱模式。
基金supported by National Natural Science Foundation of China (Grant Nos. 40773046 and 10621303)Minor Planet Foundation of China
文摘Six tektites from Guilin of Guangxi, Hainan, and Guangdong were analyzed for the abundances of major elements and 27 trace elements. All samples are splash-form tektites and have SiO2 contents ranging from 73.1wt% to 76.0wt% (74.6wt% on average). The chemical compositions, except Cr and Ni, of tektites from different areas, are similar. Guangdong tektite shows enrichments of Ni and Cr contents by a factor of 3, and has slightly higher MgO and FeO than Hainan and Guilin tektites. It indicates that the tektites were formed by mixing several target rocks. The major and trace element concentrations of southern China tektites closely resemble previously reported data for average splash-form and Muong Nong-type indochinites, indicating that they have the same source. (La/Lu)CI (7.99), Zr/Hf (35.45 on average), Ba/Rb (3.59 on average), and the rare earth element (REE) contents of tektites are similar to those of typical post Archean upper crustal rocks. This study suggests that the best fit for the target source of southern China tektites could be a combination of 41% shale, 2% sandstone, 20% greywacke, and 37% quartzite.
