C.Y. Feng’s research while affiliated with Chinese Academy of Geological Sciences and other places

Located in Qimantage area of southwest Qaidam basin, Kaerqueka copper polymetallic deposit is a characteristic hydrothermal vein-skarn ore deposit controlled by the fractured and altered zone. Two kinds of wall-rock alterations can be recognized in the ore deposit, i. e., skarn and phyllic alteration. The former was formed by intrusion of Indosinian porphyaceous biotite adamellite. Copper polymetallic skarn lenticular bodies are commonly seen in the contact zone of the intrusion, different lithologic interfaces and faulted structural zones of the surrounding rocks. There are some typical calcium skarn minerals, such as diopside, hedenbergite, andradite, hessonite, idocrase, wollastonite, epidote, scapolite and actinolite. The latter forms many parallel NWW-striking chacopyritized hydrothermal alteration zones in porphyaceous biotite adamellite in the northwest part of the ore district, belonging to hydrothermal vein type mineralization controlled by faulted fractured zones. It is concluded that Kaerqueka copper polymetallic deposit is related to Indosinian hypabyssal and high emplacement porphyaceous biotite adamellite. The ages of rocks and ores in the copper polymetallic skarn deposit and the veinlet-disseminated hydrothermal veinlike copper deposit are the same, and the backgrounds of tectono-magmatic activities are identical; nevertheless, they are products of different ore-forming processes that occurred at different stages, different depths and different parts. This ore deposit is a compound one, with the skarn copper polymetallic mineralization as the main body, accompanied by the hydrothermal vein type copper mineralization in well-developed faults of the parent rock.

Located in Qimantage area of Qinghai Province, Hutouya is a typical skarn lead-zinc polymetallic ore district consisting of both ortho-contact and exocontact substyles. The basic geological characteristics and ages of petrogenesis and mineralization were studied. The ore-forming elements are quite complex, dominated by Fe, Cu, Sn, Mo, Pb and Zn. Mineralization occurs in the contact zone between the intermediate-acidic intrusive rock and the carbonate-bearing strata, the fault zone or discordant contact between strata of different epochs and the lithologic boundaries, showing obvious zonation of mineralization and alteration from the intrusive rock outwards. U-Pb dating of zircons from granodiorite and adamellite has yielded ages of (235.4±1.8) Ma and (219.2±1.4) Ma, respectively. Re-Os isotopic dating of molybdenite from the skarn Cu-Mo polymetallic ore and skarn molybdenite ore by ICP-MS has yielded isochron ages of (225.0±4.0) Ma and (230.1±4.7) Ma. These new age data, combined with data available, indicate that the ages of ores and related granites should be Middle to Late Triassic. Indosinian magmatism and mineralization occurred at the post-collisional stage of the orogen, corresponding to the late stage of the Late Paleozoic-Early Mesozoic tectonic event in eastern Kunlun orogenic belt.

The age of tungsten mineralization and petrogenesis of its metallogenetic granitoids, and tectonic environment of the Jiulongnao tungsten orefield in southern Jiangxi Province are studied based on the field investigations and analysis on major-, trace-, and rare earth elements and dating. The Jiulongnao granite is characterized by high silica, alkali, metaluminous to weakly peraluminous, low Ca, Mg, and K2O/Na2O > 1. It also has relatively high LILE (Rb, K), but low LILE (Ba, Sr), and high HFSE (Th, U, Ce, Y, Sm, Nd, Ta, Hf), low HFSE (Nb, P). In addition, Jiulongnao granite shows strong negative Eu anomalies (δEu=0.07-0.10) and high ratios of 10 000Ga/Al (2.76-2.93). Geochemical features of Jiulongnao granite indicate that it belongs to the A-type. The SHRIMP UPb dating of zircon from Jiulongnao granite yields an age of (155.8 ± 1.2) Ma. Re-Os isotopic dating of molybdenite from the Hongshuizhai greisen-type tungsten deposit by ICPMS yields a weighted mean age of (156.3 ± 1.3) Ma, which is consistent with diagenetic age of Jiulongnao granite. Combined with chronological data of Chongyi-Dayu-Shangyou tungsten-tin polymetallic ore concentration area, we conclude that the age of both diagenesis and mineralization of this area are mainly concentrated in 150 to 160 Ma, which is corresponding to the time of the second regional large-scale mineralization in the Mesozoic and these mineralization occurred at the same geodynamic background that is Jurassic intraplate extensional environment during the large-scale extension period of lithosphere.

Based on some fieldwork and geochemical analyses in recent years, the metallogenic setting, major types, basic geological characteristics, time-space distribution and metallogeneses of polymetallic deposits (occurrences) in the Qimantage metallogenic belt, Eastern Kunlun area are described briefly in this paper. The ore-forming elements are comprehensive and dominated by Fe, Cu, Pb, Zn, Mo, W, Sn and Au. Several various styles of polymetallic mineralization in the Qimantage metallogenic belt have been recognized and Clasified into the skarn-type deposit, porphyry deposit, hydrothermal superimposed stratabound deposit and hypothermal deposit. Two important mineralization ages of both Middle-Late Triassic and early Paleozoic for polymetallic deposits are determined in the belt. For Middle to Late Triassic porphyry and skarn-type deposits, the ore-forming materials were mainly derived from magmatic and carbonate-bearing strata, and ore-forming fluids came chiefly from magmatic fluids; and both of them belong to products of the same tectonomagmatic cycle of Triassic period, although they formed in different stage, different depth and different place.