河北大庙Fe-Ti-P矿床中铁钛磷灰岩的成因: 来自磷灰石的证据

铁钛磷灰岩仅由磷灰石和铁钛氧化物组成，常赋存于岩体型斜长岩中，成因上有不混溶和分异堆晶两种不同的认识。本文从磷灰石角度讨论河北大庙铁钛磷灰岩的形成机制。大庙铁钛磷灰岩常产出于浸染状Fe—P矿体内部，有时与块状铁矿石交互出现形成韵律条带状矿石，为岩浆结晶分异的产物。铁钛磷灰岩中磷灰石呈浑圆状，含量变化于15％-34％。铁钛磷灰岩的全岩和磷灰石微量元素分析显示，磷灰石比全岩相对富集稀土元素达2．96—6．93倍，但两者的配分型式基本平行。质量平衡计算（Rocl／F）的结果表明，铁钛磷灰岩中几乎100％的稀土元素赋存于磷灰石中。综合上述特征，反映磷灰石为结晶分离的堆晶矿物，铁钛磷灰岩应为堆晶成因。因为如果磷灰石结晶于铁钛磷灰岩不混溶熔体，它的稀土元素分配系数也不会变化达2．3倍（变化于2．96—6．93）。计算出该磷灰石的母岩浆稀土元素组成，与浸染状Fe．P矿石最为相似，结合它与铁钛磷灰岩之间紧密共生的野外特征以及相似的全岩及磷灰石稀土元素配分型式，认为磷灰石最可能是在浸染状Fe．P矿浆中，经结晶分离作用形成铁钛磷灰岩。

Genesis of nelsonite from the Damiao Fe-Ti-P deposit, Hebei Province, China: Evidence from apatite

Nelsonites,which consist essentially of Fe-Ti oxides and apatite,are spatially and temporally associated with Proterozoic massif-type anorthosites,and have been interpreted as either cumulate rocks or the products of immiscible melts.The Damiao anorthosite massif in Hebei Province in China,contains numerous disseminated and vein-type Fe-Ti oxide and apatite orebodies.The disseminated ores are hosted in homogeneous silicate rocks,whereas the vein-like bodies occur as veins,lenses and rhythmic layers of massi...