Abstract: A review of Permian fusuline biostratigraphy is made in this paper in order to improve the correlation of Permian strata globally. Permian fusuline biostratigraphy in the Tethyan and Panthalassan regions can be correlated roughly because the fusulines had good faunal communications between these two regions. However, fusuline faunas from the North American Craton region were devoid of almost all neoschwagerinids and dominated exclusively by schwagerinids during the Guadalupian (Middle Permian) because of the blockage caused by the vast Pangaea supercontinent. This renders the correlation of Middle Permian biostratigraphy and chronostratigraphy between the Tethyan region and North American region challenging. Significant evolutionary key points in fusulines include the first occurrence of Pseudoschwagerina or Sphaeroschwagerina during the earliest Permian, first occurrence of Pamirina and Misellina during the Yakhtashian and Bolorian, and the extinction of all schwagerinids and neoschwagerinids by the end of the Midian.

Abstract The Carboniferous and Permian systems are important components of the basement rocks in Thailand and crop out widely. The exceptions are the Khorat Plateau, where they occur in the subsurface but are concealed beneath a thick Mesozoic cover, and in the Chao Phraya Central Plain where they are largely covered by Quaternary sediments but crop out in scattered monadnocks (Fig 5.1 ). Most Carboniferous and Permian rocks are of shallow-marine facies although siliceous sediments of ancient ocean-bottom origin are also known in places. Continental deposits are quite rare. The Carboniferous System is dominated by siliciclastic rocks except in northernmost Thailand around the Chiang Mai-Mae Hong Son area where there are large carbonate bodies. In contrast, carbonates are the dominant lithology in the Permian System, forming characteristic karst topography in the tropical humid climate. It has been quarried in some areas, such as Saraburi and Ratchaburi, for flagstones and cement production. In the 1970s and 1980s the Department of Mineral Resources (DMR), Thailand, published a series of 1:250 000 scale geological maps covering the whole of Thailand. That stratigraphic information laid the groundwork for a number of papers on the Carboniferous and Permian systems of this country ( Bunopas 1981 , 1983 , 1992 , 1994 ; DMR 2001 , 2007 ; Raksaskulwong 2002 ; Assavapatchara et al. 2006 ). In parallel with those stratigraphical works, more palaeontological aspects of Carboniferous and Permian strata were summarized ( Toriyama et al. 1975 ; Ingavat

Abstract Skarn deposits are one of the most common deposit types in China. The 386 skarns summarized in this review contain ~8.9 million tonnes (Mt) Sn (87% of China’s Sn resources), 6.6 Mt W (71%), 42 Mt Cu (32%), 81 Mt Zn-Pb (25%), 5.4 Mt Mo (17%), 1,871 tonnes (t) Au (11%), 42,212 t Ag (10%), and ~8,500 Mt Fe ore (~9%; major source of high-grade Fe ore). Some of the largest Sn, W, Mo, and Zn-Pb skarns are world-class. The abundance of skarns in China is related to a unique tectonic evolution that resulted in extensive hydrous magmas and widespread belts of carbonate country rocks. The landmass of China is composed of multiple blocks, some with Archean basements, and oceanic terranes that have amalgamated and rifted apart several times. Subduction and collisional events generated abundant hydrous fertile magmas. The events include subduction along the Rodinian margins, closures of the Proto-Tethys, Paleo-Asian, Paleo-Tethys, and Neo-Tethys Oceans, and subduction of the Paleo-Pacific plate. Extensive carbonate platforms developed on the passive margins of the cratonic blocks during multiple periods from Neoarchean to Holocene also facilitated skarn formation. There are 231 Ca skarns replacing limestone, 15 Ca skarns replacing igneous rocks, siliciclastic sedimentary rocks, or metamorphic silicate rocks, 113 Ca-Mg skarns replacing dolomitic limestone or interlayered dolomite and limestone, and 28 Mg skarns replacing dolomite in China. The Ca and Ca-Mg skarns host all types of metals, as do Mg skarns, except for major Cu and W mineralization. Boron mineralization only occurs in Mg skarns. The skarns typically include a high-temperature prograde stage, iron oxide-rich higher-temperature retrograde stage, sulfide-rich lower-temperature retrograde stage, and a latest barren carbonate stage. The zoning of garnet/pyroxene ratios depends on the redox state of both the causative magma and the wall rocks. In an oxidized magma-reduced wall-rock skarn system, such as is typical of Cu skarns in China, the garnet/pyroxene ratio decreases, and garnet color becomes lighter away from the intrusion. In a reduced intrusion-reduced wall-rock skarn system, such as a cassiterite- and sulfide-rich Sn skarn, the skarn is dominated by pyroxene with minor to no garnet. Manganese-rich skarn minerals may be abundant in distal skarns. Metal associations and endowment are largely controlled by the magma redox state and degree of fractionation and, in general, can be grouped into four categories. Within each category there is spatial zonation. The first category of deposits is associated with reduced and highly fractionated magma. They comprise (1) greisen with Sn ± W in intrusions, grading outward to (2) Sn ± Cu ± Fe at the contact zone, and farther out to (3) Sn (distal) and Zn-Pb (more distal) in veins, mantos, and chimneys. The second category is associated with oxidized and poorly to moderately fractionated magma. Ores include minor porphyry-style Mo and/or porphyry-style Cu mineralization ± Cu skarns replacing xenoliths or roof pendants inside intrusions, zoned outward to major zones of Cu and/or Fe ± Au ± Mo mineralization at the contact with and in adjacent country rocks, and farther out to local Cu (distal) + Zn-Pb (more distal) in veins, mantos, and chimneys. Oxidized and highly fractionated magma is associated with porphyry Mo or greisen W inside an intrusion, outward to Mo and/or W ± Fe ± Cu skarns at the contact zone, and farther to Mo or W ± Cu in distal veins, mantos, and chimneys. The final category is associated with reduced and poorly to moderately fractionated magma. No major skarns of this type have been recognized in China, but outside China there are many examples of such intrusions related to Au-only skarns at the contact zone. Reduced Zn-Au skarns in China are inferred to be distal parts of such systems. Tungsten and Sn do not occur together as commonly as was previously thought. The distal part of a skarn ore system may transition to carbonate replacement deposits. Distal stratabound mantos and crosscutting veins/chimneys may contain not only Zn-Pb but also major Sn, W, Cu, Mo, and Au mineralization. The Zn-Pb mineralization may be part of either an oxidized system (e.g., Cu, Mo, Fe) or a reduced system (e.g., Sn). In China, distal Zn-Pb is more commonly related to reduced magmas. Gold and W may also be related to both oxidized and reduced magmas, although in China they are more typically related to oxidized magma. There are numerous examples of distal mantos/chimneys that continuously transition to proximal skarns at intrusion-wall-rock contact zones, and this relationship strongly supports the magmatic affiliation of such deposits and suggests that distal skarns/carbonate replacement deposits systems should be explored to find more proximal mineralization. Carbonate xenoliths or roof pendants may host the majority of mineralization in some deposits. In contact zones, skarns are better developed where the intrusion shape is complicated. The above two skarn positions imply that there may be multiple skarn bodies below drill interceptions of intrusive rocks. Many of the largest skarns for all commodities in China are related to small or subsurface intrusions (except for Sn skarns), have multiple mineralization centers, are young (<~160 Ma), and have the full system from causative intrusion(s) to distal skarns or carbonate replacement extensions discovered. Chinese skarn deposits fall in several age groups: ~830, ~480 to 420, ~383 to 371, ~324 to 314, ~263 to 210, ~200 to 83, ~80 to 72, and ~65 to 15 Ma. They are typically associated with convergent plate boundaries, mostly in subduction settings but also in collisional settings. Seven major skarn metallogenic belts are recognized based on skarn geographic location and geodynamic background. In subduction settings, skarns may form in a belt up to 4,000 km long and 1,000 km inland, with skarns continuously forming for up to 120 m.y., e.g., the eastern China belt. In most other belts, skarns form in 5- to 20-m.y. episodes similar to the situation in South America. In collisional settings, skarns may form up to 50 m.y. after an ocean closure, and the distance to the collisional/accretionary boundary may extend to ~150 km inland. The size of collision-related skarns may be as large as the largest skarns related to oceanic crust subduction. Older suture zones may be favorable sites for younger mineralization, for example, the Triassic Paleo-Tethys suture between the North and South China blocks for the younger and largest skarn cluster of the Middle-Lower Yangtze belt in the eastern China belt, and the Triassic sutures in southwestern China for Cretaceous to Tertiary mineralization.

Abstract Tungsten and Sn deposits in China are widely distributed in the South China block (i.e., Yangtze craton-Cathaysian block), Himalaya, Tibetan, Sanjiang, Kunlun, Qilian, Qinling, Dabie, and Sulu orogens, and Central Asian orogenic belt. Among these, the South China block hosts the majority of the mineralization with about 73% (9.943 million tonnes WO 3 ) and 85% (6.561 million tonnes Sn) of the country’s total W and Sn resources, respectively. The W resource mainly occurs as skarn (63%), quartz-vein (17%), porphyry (17%), and greisen (3%) Sulu deposits, whereas Sn is present in skarn (81%), quartz veins that are typically tourmaline-bearing (6%), sulfide-rich veins or mantos (5%), greisen (5%), and porphyry (3%) Sulu deposits. The W and Sn mineralization formed during numerous events from Neoproterozoic to Paleocene with a peak in the period from the Middle Jurassic to Early Cretaceous, and with an uneven spatial and temporal distribution pattern. The Neoproterozoic Sn (W) deposits (850–790 Ma) occur on the southern and western margins of the Yangtze craton, the early Paleozoic W(Sn) deposits (450–410 Ma) are mainly distributed in the northern Qilian and the westernmost part of the eastern Kunlun orogens, the late Paleozoic Sn and W deposits (310–280 Ma) are mainly developed in the western part of the Central Asian orogenic belt, the Triassic W and Sn deposits (250–210 Ma) are widely scattered over the whole country, the Early Jurassic to Cretaceous W and Sn deposits (198–80 Ma) mainly occur in eastern China, and the late Early Cretaceous to Cenozoic Sn and W deposits (121–56 Ma) are exposed in the Himalaya-Tibetan-Sanjiang orogen. The petrologic characteristics of W- and Sn-related granitoids in China vary with the associated ore elements and can be divided into the Sn-dominant, W-dominant, W-Cu, and Mo-W (or W-Mo) groups. The granitoids associated with the Sn- and W-dominant magmatic-hydrothermal systems are highly fractionated S- and I-type, high-K calc-alkaline and (or) shoshonitic intrusions that show a metaluminous to peraluminous nature. They exhibit enrichments in F, B, Be, Rb, Nb, and Ta, depletions in Ti, Ca, Sr, Eu, Ba, and Zr, and strongly negative Eu anomalies. The granitoids associated with W-Cu and W-Mo deposits are of a high-K calc-alkaline to shoshonitic nature, metaluminous, depleted in Nb and Ta, and display weakly negative Eu anomalies. Granitoids associated with Sn- and W-dominant deposits are reduced, whereas those linked to W-Cu and Mo-W deposits are relatively more oxidized. The magma sources of W-dominant granitoids are ancient crust, whereas those connected with Sn, Mo-W, and W-Cu deposits are from variable mixing of ancient and juvenile crustal components. The spatial and temporal distribution pattern of W and Sn deposits in China is intimately related to the regional geodynamic evolution. The Neoproterozoic Sn deposits are associated with peraluminous, highly fractionated, and volatile-enriched (boron and fluorine) S-type granites sourced from the melting of an ancient crust in a postcollisional setting related to the assembly of the Rodinia supercontinent. The early Paleozoic W deposits are genetically associated with highly fractionated S-type granites formed during postcollisional events and were derived from the partial melting of a thickened continental crust in the context of Proto-Tethyan assembly. Granitoids associated with late Paleozoic Sn and W deposits were derived from the melting of an ancient and juvenile crust with I-type affinity associated with the closure of the Paleo-Asian Ocean. Although the Triassic W and Sn deposits are related to the assembly of Asian blocks within the Pangea supercontinent, their geologic settings are variable. Those in the South China block and the Himalaya-Tibetan-Sanjiang belt are associated with collision and magma derivation through the partial melting of a thickened continental crust, whereas in the Kunlun-Qilian-Qinling-Dabie-Sulu orogen and the Central Asian orogenic belt, a postcollisional extensional setting dominates. The Early Jurassic (198–176 Ma) W deposits, located in the northern part of northeast China, are associated with highly fractionated I-type granites derived from melting of juvenile crust and emplaced during the subduction of the Mongol-Okhotsk oceanic plate. The extensive group of Middle Jurassic to Cretaceous W and Sn deposits formed at two stages at 170 to 135 and 135 to 80 Ma. The former stage is associated with highly fractionated S- and I-type granites that are the products of partial melting of thickened crust with heat input possibly derived from a slab window associated with the Paleo-Pacific oceanic plate subduction beneath the Eurasian continent. The later stage is closely associated with NNE-trending strike-slip faults along the Eurasian continental margin and is coeval with the formation of rift basins, metamorphic core complexes, and porphyry-epithermal Cu-Au-Ag deposits. These processes, which were instrumental for the formation of a wide range of mineral deposits, can be ascribed to the regional lithospheric thinning and delamination of a thickened lithosphere and thermal erosion in a postsubduction extensional setting. The 121 to 56 Ma Sn deposits in the Himalaya-Tibetan-Sanjiang orogen are associated with S-type granite or I-type granodiorite emplacement in a back-arc extensional setting during Neo-Tethys plate subduction.