原子序数从64～71，加上39号元素，钆(Gd)、铽(Tb)、镝(Dy)、钬(Ho)、铒(Er)、铥(Tm)、镱(Yb)、镥(Lu)和钇(Y)称，为重稀土元素，又称钇组元素(yttrium group)。
稀土元素通常是同时被发现的，一般来说轻稀土元素的数目远甚于重稀土元素。
Rare earth metals are often all found together, typically with far more light than heavy elements.
随着时代变新，玄武岩碱性逐渐增强，轻、重稀土元素分离程度及不相容元素富集程度也逐渐增强。
With the ages becoming younger of the basalts, their alkali, the fractional degree of LREE/ HREE and incompatible elements enrichment increased.
研究表明玄武岩首先风化形成蒙皂石族粘土矿物，在此过程中稀土元素没有明显的分馏作用，强风化的玄武岩重稀土元素强烈亏损；
It is concluded that the half-weathered basalts have not distinct REE fractionation and strong weathered basalts had HREE loss in the process of the basalts weathered to form smectite family minerals.
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