四川盆地紫色母岩中钛与母岩原始风化度关系的研究

TITANIUM IN PURPLE PARENT ROCK AND WEATHERING DEGREE OF THE ROCK IN SICHUAN BASIN

用（NH4）2SO4-浓H2SO4-二胺替吡啉甲烷比色法和NaOH熔融-二胺替吡啉甲烷比色法，分别提取和测定了四川盆地几种主要紫色母岩和土壤中无定型TiO2和全钛。将“全TiO2／无定型TiO2”定义为“钛值”，并用钛值代替硅铝铁率衡量紫色母岩的风化程度。结果为：四川盆地的六种紫色母岩中全钛含量变化于2．95～20．0gkg^-1（TiO2）之间，属中等偏高水平；不同岩性间趋势为泥页岩〉泥岩〉粉砂岩〉砂岩；全量TiO2与岩石的总SiO2含量呈显著的负相关（r=-0．7459^＊）。钛值的大小与风化度呈反相关，按钛值的大小，各紫色母岩原始风化度大小顺序如下：三叠纪飞仙关（T1f）〈侏罗纪沙溪庙（J2s）〈侏罗纪自流井（J1-2z）〈侏罗纪蓬莱镇（J3p）〈侏罗纪遂宁组（J3s）〈白垩纪夹关组（K2j）。紫色土壤钛值所反映的风化度与硅铝铁率基本吻合，二者的相关性达到极显著水平（r=0．8615^＊＊）。而土壤胶体的钛值与硅铝铁率的相关系数r=0．8757^＊＊，达极显著相关。土壤钛值所反映的风化度水平与紫色母岩的风化度趋势一致。

The methods of （NH4）2SO4-H2SO4-diantipyryl methane colorimetry and NaOH melting-diantipyryl methane colorimetry were used separately to extract and determine the amorphous titanium and total titanium in some purple parent rocks and soils in the Sichuan Basin. The total/amorphous titanium was defined as ＂titanium value＂, which was used for estimating weathering degree of purple parent rocks instead of SiO2/（ Al2O3 ＋ Fe2O3 ） value. The results show that of the contents of total titanium in six purple parent rocks in the Sichuan Basin varied in the range of 2.95· 20.0 g kg^-1, which is a middle level on the high side, and the six parent rocks in terms of lithology were in a decreasing order of shale 〉 mudstone 〉 siltstone 〉 sandstonem. The total titanium was obviously in negative correlation （ r = - 0. 745 9 ^＊ ） with SiO2 in these rocks. Titanium value was reversibly correlated to weathering degree. According to the titanium value of the rocks, weathering degree of the six purple parent rocks were lined in an rising order of Trias T1f〈 Jurassic J2s 〈 Jurassic J1.2z 〈 Jurassic J3 P 〈 Jurassic J2sn 〈 Cretaceous K2j. The order of weathering degree of the purple soils based on titanium values basically tallied with that based on SiO2/（Al2O3 ＋ Fe2O3） values, with correlation coefficient reaching an obvious level （ r = 0. 861 5^＊＊ ）. The correlation coefficient between the titanium value of soil colloid and the SiO2/（Al2O3 ＋ Fe2O3） value also reached an obvious level （ r = 0.875 7^＊＊ ）. The weathering degree showed by the titanium value of the soil is in accord with that showed by purple parent rocks.