Fluid inclusions in the mesozonal gold deposit at Atud mine, Eastern Desert, Egypt
Gold mineralization at the Atud mine occurs as fracture-filling auriferous quartz veins hosted in Neoproterozoic dioritic rocks and along their contact with metagabbro. Gold mineralization is associated with metasomatic alteration zones around shear zones and quartz–carbonate vein arrays. The mineralized veins consist of quartz, carbonate and albite gangue enclosing minor amounts of pyrrhotite, arsenopyrite, pyrite and sphalerite. Trace amounts of galena, chalcopyrite, magnetite and rutile are also present. Paragenetically, the mineralization is divided, with decreasing temperature, into three stages, namely: (1) Early (Au-poor, pyrrhotite–arsenopyrite–pyrite–quartz vein); (2) Main (Au-rich, sphalerite–arsenopyrite–pyrite–galena ± chalcopyrite–quartz vein); and (3) Late (quartz–carbonate–pyrite ± galena). 
 
Gold (15.6–36.2 at.% Ag) is present mainly as discrete grains of native gold (<5–20 μm in diameter). Free gold appears mainly as inclusions in quartz and as microscopic inclusions (<5 μm) in arsenopyrite and pyrite. Gold also occurs in fractures and grain boundaries of pyrite, arsenopyrite and base metal sulphides. These occurrences of gold indicate that several influxes of gold and/or stages of remobilization took place. 
 
Based on temperatures inferred from arsenopyrite compositions by electron microprobe, the estimated temperatures for Early and Main mineralized stages reach 340–430, and 273–368 °C, respectively. The sulphur activity (atm) of ore formation at the Atud deposit was estimated for each stage as 10−6.5–10−9.6, and 10−8–10−12.2, respectively. 
 
Fluid inclusions in quartz intimately associated with the mineralization are dominated by aqueous H2O–CO2 + NaCl types. In most cases, these fluid inclusions co-exist in individual samples and show various CO2 phase volume proportions at 40 °C. Co-existing H2O-rich liquid and CO2-rich vapour fluid inclusions homogenized into liquid and carbonic vapour phases, respectively, over the same temperature range (270–490 °C). The petrographic observations and microthermometric data suggest that fluid inclusions in quartz intimately associated with the early and main mineralizing events were trapped during phase separation of an originally homogenous H2O–CO2 liquid, with low salinity (2.8–8.2 wt.% NaCl equiv.) and high density of 0.8–0.9 g/cc (corresponding to 15–76 mol% CO2). These data are consistent with transportion of gold as a bisulphide complex. Gold deposition occurred over a temperature range of 270–430 °C and pressures of 160–272 MPa (∼6–11 km depths), likely due to decreases in sulphur activity (10−6.5–10−12.2) accompanying fluid unmixing. Gold deposition in the Atud diorites was related to fluid phase separation, sulphidization and carbonatization of host dioritic rocks during hydrothermal alteration and mineralization. The diorites are considered to have acted as preferential sites for fluid flow and ore precipitation due to their brittle nature during regional deformation.
Analytical study of the Middle Kingdom group of gold jewellery from tomb 124 at Riqqa, Egypt
The jewellery from tomb 124 at Riqqa, consisting of one pectoral and one winged beetle in gold and cloisonne work, one gold shell pendant decorated with wires and granulation, and one hollow gold amulet in the form of god Min, was analysed by handheld X‐ray fluorescence and scanning electron microscopy with energy‐dispersive X‐ray spectroscopy. This group of jewellery, dated to the second half of the 12th Dynasty (c. 1900–1840 B.C.), was excavated inside the coffin of an adult male, which had been crushed after burial by the collapse of the chamber roof during an episode of looting. Both the male and the looter's body were found inside the chamber, evidencing that the group of jewellery was intact. Despite having been highly restored in the past, as referenced in the correspondence between the excavator Flinders Petrie and the curators of the Manchester Museum, it could be shown that the jewellery was produced using Ag‐rich electrum alloys containing platinum group element inclusions that indicate the use of alluvial gold. The analysis of some joins has confirmed the use of hard‐soldering, with solders obtained by addition of Cu to the base‐alloy. Data obtained for the jewellery of tomb 124 were compared with data previously obtained for tomb 296, also excavated at Riqqa, but dated to the 18th Dynasty. The comparison demonstrates the continuity of the workshop traditions in one location between the Middle Kingdom and the New Kingdom but also reveals discrepancies in the alloys employed in those two periods.
Structural evolution of the Port Wells gold mining district, Prince William Sound, south central Alaska: Implications for the origin of the gold lodes
Data collected in the Port Wells gold mining district, Alaska, indicate several stages in the structural history of the district. The first stage was the accretion and associated deformation of the Valdez group flysch sequence at the end of the Cretaceous. The deformation of the semilithified rocks included two folding phases forming isoclinal NE-SW-striking and SE-vergent folds during a D1 phase, and minor open warps in NW-SE direction during a D2 phase. Intrusion of early Oligocene (36 Ma) calc-alkaline granitoids followed deformation and was terminated by the emplacement of aplitic dikes. The major fracturing processes in both the granitoids and the country rocks occurred subsequently, probably during the uplift of the Chugach mountains in the late Tertiary. Several generations of epigenetic gold-bearing quartz veins were emplaced along the fractures at a later stage. Due to the significant time gap between peak metamorphism and mineralization, the metamorphic secretion model proposed for the vein formation is reconsidered.