北大别罗田超高压榴辉岩中峰期变质矿物:褐帘石和氟磷灰石  

Allanite and fluor-apatite formed under ultrahigh-pressure conditions from the Luotian eclogites in the North Dabie complex zone

作　　者：刘贻灿[1] 古晓锋[1] 李曙光[1] 陈振宇[2] 

机构地区：[1]中国科学院壳幔物质与环境重点实验室中国科学技术大学地球和空间科学学院,安徽合肥230026 [2]中国地质科学院矿产资源研究所,北京100037

出　　处：《中国科学技术大学学报》2007年第8期933-939,共7页JUSTC

基　　金：国家自然科学基金(40572035和40634023)资助

摘　　要：对北大别西南部＂罗田穹隆＂中超高压榴辉岩进行了变质岩石学研究,发现其中含有褐帘石和氟磷灰石.褐帘石主要以包体形式产出于石榴子石中,富含稀土元素,部分已退变为绿帘石;氟磷灰石主要以包体形式产出于石榴子石中或存在于基质中,产出于石榴子石中氟磷灰石具有较高的F含量（～3 wt%）,而基质中氟磷灰石大多数具有磁黄铁矿针状出溶体及相对低的F含量（～1 wt%）.根据石榴子石中与褐帘石、氟磷灰石共生的包体矿物组合以及氟磷灰石中较高的F含量,证明它们形成于超高压条件下.由此提出了罗田榴辉岩曾发生超高压变质作用的新证据.Metamorphic petrology of eclogites at Luotian from the southwestern part of the North Dabie complex zone, central China, was studied. It was found that except for usual eclogitic minerals such as garnet, omphacite and futile, the eclogites contain allanite and fluor-apatite. Allanites are rich in rare earth elements （REE） and occur as inclusion in garnet, and some of them were partly retrogreted to epidote. Whereas fluor （F）-apatite occurs as inclusion in garnet or in matrix, the former is rich in F （-3 wt%） without any exsolutions and the latter is relatively poor in F （-1 wt%） associated with the oriented pyrrhotite exsolution. In view of occurrence and assemblage of the coexisting minerals with allanite and fluor-apatite in garnet, it is suggested that they formed at peak stage of ultrahigh-pressure （UHP） metamorphism. These results provide new evidence that UHP metamorphism occurred in the eclogites at the Luotian dome.

关 键 词：超高压变质作用 褐帘石 氟磷灰石 榴辉岩 北大别杂岩带 

分 类 号：P588.3[天文地球—岩石学] P59[天文地球—地质学]