中国主要陆块特定时段的漂移演化历史及其对海相钾盐成矿作用的制约

Drifting history of China's main blocks during specific periods and its tectonic constraints on marine potash formation

中国钾盐资源匮乏,目前陆相钾盐资源已基本探明,但海相找钾还没有取得重大进展,然而,要想建立适合中国小陆块海相成钾理论框架,实现海相找钾突破,一个重要基础性工作是确定特定时段中国小陆块典型海相盆地的古地理纬度。而古地磁学是确定陆块的纬向运动,开展古地理重建的最有效手段。文章针对中国4类成钾潜力较高的典型海相盆地所属陆块——华北、华南、羌塘、兰坪-思茅陆块,通过收集、评价和筛选以往古地磁研究成果,总结了这些陆块在主要成盐成钾阶段的古纬度变迁历史,确定华北陆块(绥德)在中、晚奥陶世的古纬度为9.2°S^14.2°S,华南陆块(成都)在三叠纪的古纬度为10.6°N^23.1°N,羌塘陆块(雁石坪)在中、晚侏罗世的古纬度为14.6°N^27.5°N,兰坪-思茅盆地(江城)在白垩纪至古新世的古纬度为20.9°N^27.6°N。同时,为了更好地探讨兰坪-思茅盆地的成钾潜力,对与其相邻的已发现巨型钾盐矿床的印度支那块体开展了相应时段的古纬度研究,确定该陆块(万象)在白垩纪的古纬度约为21.1°N^21.3°N。最后,综合古纬度和其他地质证据,从大地构造背景上探讨了4个陆块的成盐、成钾条件。

In view of severe potash shortage with extensively explored terrestrial potash, no significant progress has been made in the marine potash in China. To construct a suitable theoretical framework and find out new marine potash resources in China, one of the keys is to determine the paleo-latitudes ol the specltac perloas ot several high-potential marine potash rich blocks. Paleomagnetism is one of the most effective methods in determining latitudinal drift of blocks. In this paper, we evaluated and summarized the existing paleomagnetic results of four representative blocks in China, North China （NCB）, South China （SCB）, Qiangtang （QTB）, and Lan-ping-Simao （LSB） blocks, as well as the adjacent Indochina Block （ICB）, to establish better resolution paleolatitudes of specific potential potash-halite rich periods. The results reveal paleolatitudes of 9.2°S- 14.2°S for the early-middle Ordovician NCB （Suide）, 10.6°N--23.1°N for the Triassic SCB （Chengdu）, 14.6°N- 27.5°N for the Middle-Late Jurassic QTB （Yanshiping）, 20.9°N- 27.6°N for the Cretaeeous-Paleocene LSB （Jiangcheng）, and 21.1°N--21.3°N for the Cretaceous ICB （Vientiane）. Combined with the above mentioned paleolatitudes with other related geological evidences, the potentials of potash-halite formation of the five blocks of their related periods are discussed in the end.