Five generations of fluorapatite in mineralized skarn and host rocks from the Mactung W (Cu-Au) deposit, Northwest Territories, Canada, are identified based on petrographic, compositional and geochronological (U–Pb) data. These data, coupled with new (in this study) and previously published data on apatite from the nearby Cantung deposit, provide constraints on the timing of skarn mineralization, as well as metal and fluid sources of the Canadian Tungsten Belt. Type-i apatite of the Mactung deposit formed from ~ 106 ± 4 to 103 ± 2 Ma through recrystallization of sedimentary apatite (type-o apatite) during regional metamorphism, pre-skarnification. Type-i apatite is W-rich (up to 47.6 ppm) and occurs with coeval scheelite and titanite, indicating a potential sedimentary source, perhaps from detrital rutile, for W. Apatite crystals in prograde (type-ii) and retrograde (type-iii and type-iv) skarns yield ages from ~ 96 ± 1 to 92 ± 1 Ma, overlapping with Mactung biotite-granite plutons and late-stage felsic dykes and confirming skarn formation during emplacement of the granites over a period of ~ 5 million years. Type-ii apatite contains high rare earth element that increases with increasingly negative Eu anomalies, suggesting prograde fluids were sourced from a felsic melt undergoing fractional crystallization. Retrograde apatite exhibits weak lanthanide tetrad effects with superchondritic Y/Ho ratios (> 38), suggesting retrograde fluids exsolved from a highly evolved magmatic source. Apatite crystals from the Cantung skarn deposit are compositionally and paragenetically similar to those from the Mactung apatite and yield ages similar to the Cantung biotite-monzogranite plutons and late-stage felsic dykes. We conclude prograde fluids were derived from biotite-granites, whereas retrograde fluids exsolved from evolved melts recorded by later felsic dykes.

根据岩石学、成分和地质年代学 (U-Pb) 数据，确定了加拿大西北地区 Mactung W (Cu-Au) 矿床的矿化矽卡岩和主岩中的五代氟磷灰石。这些数据，加上新的（在本研究中）和先前发表的来自附近 Cantung 矿床的磷灰石数据，限制了矽卡岩矿化的时间以及加拿大钨带的金属和流体来源。Mactung 矿床的 i 型磷灰石在区域变质作用、预石化作用期间通过沉积磷灰石（o 型磷灰石）的再结晶形成于约 106 ± 4 至 103 ± 2 Ma。i 型磷灰石富含 W（高达 47.6 ppm），并与同时代的白钨矿和榍石一起出现，表明 W 的潜在沉积来源，可能来自碎屑金红石。顺行（ii 型）和逆行（iii 型和 iv 型）矽卡岩中的磷灰石晶体产生的年龄从 ~ 96 ± 1 到 92 ± 1 Ma，与 Mactung 黑云母-花岗岩岩体和晚期长英质岩脉重叠并证实了矽卡岩在大约 500 万年的时间里花岗岩就位期间形成。II型磷灰石含有高稀土元素，随着负Eu异常的增加而增加，这表明前行流体来自经历分级结晶的长英质熔体。逆行磷灰石表现出弱的镧系元素四联体效应，超球粒状 Y/Ho 比 (> 38)，表明逆行流体从高度演化的岩浆源中溶出。Cantung 矽卡岩矿床的磷灰石晶体在成分和共生上与 Mactung 磷灰石相似，并且产生的年龄类似于 Cantung 黑云母-二长花岗岩和晚期长英质岩脉。我们得出结论，顺行流体来自黑云母花岗岩，而逆行流体则从后来的长英质岩脉记录的演化熔体中溶解出来。