华北地台西缘晚石炭世一早二叠世早期海水进退及其与聚煤作用的关系          下载免费PDF全文

彭格林  钟蓉  唐伟忠 《古地理学报》1999,(2)

从古元古代至晚古生代,华北地台西缘经历了坳拉槽、槽后坳和坳陷发育阶段.笔者在大区域地层对比及详细的沉积环境分析基础上,对晚古生代海水进退与聚煤作用关系作了较深入研究.结果表明:晚石炭世晚期至早二叠世早期华北地台西缘主要为潮坪和三角洲沉积发育区,在空间上沉积环境具有东西有别南北分带的特点;西部由潟湖潮坪沉积环境逐渐过渡为河控潟湖三角洲和受潮汐影响的河控滨海三角洲沉积环境;东部为潮坪沉积环境,东侧边缘还出现近山滨海平原沉积环境.研究区在晚石炭世早期一早二叠世早期发生过4次2级海水进退,其中第三、第四次海侵全区发育.早二叠世早期初的第三次2级海侵是最大的一次.最大海侵前夕——晚石炭世晚期末是大区域发育厚—巨厚煤层的最好时期.潟湖三角洲平原和陆源碎屑潮上泥炭坪及泥炭沼泽是最佳的聚煤场所.  相似文献   

泥炭与煤形成环境对比研究现状   总被引：9，自引：2，他引：7  

彭格林  张则有  伍大茂 《地球科学进展》1999,14(3):247-255

煤地质学一直偏重于对煤和含煤地层的地层学和沉积学的研究。近３０年来逐渐重视从现代聚煤作用产物－泥炭和泥炭沼泽的角度揭示,印证成煤环境问题。但苦于寻找古代煤层的合适的类比物。８０年代以来,人们逐渐把注意力集中在东南亚热带木本穹丘状高位泥炭的泥炭地,获得了大量数据资料和观察结果,开创了泥炭与煤形成环境对比研究的新局面。  相似文献   

Experimental investigation of reactions between two-mica granite and boron-rich fluids: Implications for the formation of tourmaline granite     

Lining CHENG  Chao ZHANG  Xiaosong YANG  Dongmei QI  Yongsheng ZHOU  Francois HOLTZ 《中国科学:地球科学(英文版)》2019,(10)

The genetic relationship between different types of granite is critical for understanding the formation and evolution of granitic magma. Fluid-rock interaction experiments between two-mica leucogranite and boron-rich fluids were carried out at 600–700°C and 200 MPa to investigate the effects of boron content in fluid and temperature on the reaction products. Our experimental results show that tourmaline granite can be produced by reactions between boron-rich fluid and two-mica granite.At 700°C, the addition of boron-rich fluid resulted in partial melting of two-mica granite and crystallization of tourmaline from the boron-rich partial melt. Increasing boron concentration in fluid promotes the melting of two-mica granite and the growth of tourmaline. No melt was produced in experiments at 600°C, in which Fe, Mg and Al released from biotite decomposition combined with boron from the fluid to form tourmaline under subsolidus conditions. The Na required for tourmaline crystallization derived from Na/K exchange between feldspar and the K released by biotite decomposition. The produced tourmaline generally has core-rim structures, indicating that the composition of melt or fluid evolved during tourmaline crystallization.Based on the experimental results, we propose that tourmaline granite veins or dikes can be formed by the reactions between boron-rich fluids, presumably produced by devolatilization of boron-bearing granitic magma, and incompletely crystallized granite at the top of the magma chamber. This "self-metasomatism" involving boron-rich fluid in the late stage of magma crystallization could be an important mechanism for the formation of tourmaline granite.  相似文献