The early Tertiary Sanerlin uranium deposit is located near the southwestern margin of the Chaling- Yongxing pull-apart basin defined by the Chaling-Yongxing and Chenxian-Linwu sinistral strike-slip faults in southern China. The uranium ores are hosted in 15 breccia-veinbodies, which are separately located in the cores of three secondary anticlines of the Upper Permian Dangchong Formation. Individual breccia-vein bodies are composed of fragments of silicified shale and sandstone from the Dangchong Formation, and quartz veinlets as cements. These fragments, together with quartz veins, form a mosaic texture. Hydrothermal pitchblende is the only commercial uranium mineral, mainly occurring as disseminated grains within quartz veins or coating fragments. Other metallic minerals include molybdenite, pyrite, chalcopyrite, galena, sphalerite, and red microcrystalline hematite. Fluid inclusions in quartz veins have homogenization temperatures ranging from 150 to 280 C, and calculated salinity values between 5.6 and 13.4wt% NaCl equivalent. Stable isotope analyses show that the mineralizing fluid was characterized by d18O values of-2.2 to +2.6 & and dDH2O values of-134 to-110 &. These analytical data demonstrate that hydrothermal fluids were mainly derived from formation waters (brines) of the Chaling-Yongxing basin. Fluid overpressuring was caused by an abnormal geothermal gradient and impermeable shales inthe deposit area. The geometry, texture, and structure of the breccia-veinsystem, along with the fluid pressure estimates, suggest that hydraulic fracturing generated the mineralized breccia-vein system. Pitchblende and associated minerals were deposited when gaseous phases were released abruptly from the ore fluids due to the hydraulic fracturing.

South China is the most important uranium producer in the country. Much of the Mesozoic-Cenozoic geology of this area was dominated by NNE-trending intracontinental strike-slip faulting that resulted from oblique subduction of the paleo-Pacific plate underneath the eastern China continent. This strike-slip fault system was characterized by transpression in the early-mid Jurassic and by transtension from the latest Jurassic through Cretaceous to early Tertiary. Most uranium ore deposits in South China are strictly fault-hosted and associated with mid-late Mesozoic granitic intrusions and volcanic rocks, which formed under transpression and transtension regimes, respectively. Various data demonstrate that the NNE-trending strike-slip faults have played critical roles in the formation and distribution of hydrothermal uranium deposits. Extensive geochronological studies show that a majority of uranium deposits in South China formed during the time period of 140 40 Ma with peak ages between 87 48 Ma, coinciding well with the time interval of transtension. However, hydrothermal uranium deposits are not uniformly distributed along individual strike-slip fault. The most important ore-hosting segments are pull-apart stepovers, splay structures, extensional strike-slip duplexes, releasing bends and fault intersections. This non-uniform distribution of ore occurrences in individual fault zone reflects localization of hydrothermal fluids within those segments that were highly dilational and thus extremely permeable. The unique geometric patterns and structural styles of strike-slip faults may have facilitated mixing of deeply derived and near-surface fluids, as evidenced by stable isotopic data from many uranium deposits in South China. The identification of fault segments favorable for uranium mineralization in South China is important for understanding the genesis of hydrothermal ore deposits within continental strike-slip faults, and therefore has great implications for exploration strategies.

The NNE-trending Hunan-Jiangxi strike-slip fault system (HJSFS) of southern China comprises three NNE-trending primary faults (the Anhua-Chengbu fault, the Chalin-Chenxian fault, and the Ganjiang fault) with associated NE-and NW-trending secondary faults. A series of linear Bouguer gravity lows coincide with these NNE-trending faults and their associated secondary ones. En echelon basins and ranges occurring at fairly regular intervals of 20-40km are strictly situated along the NE-and NNE-trending faults and within their releasing and restraining bends or stepovers, respectively. Several large streams, in general, follow the strike-slip faults. These features demonstrate a close relationship between the modern landforms and the HJSFS. Sub-linear seismically active zones and hot springs are also distributed along or adjacent to the faults, indicating this strike slip fault system is still active. The spatial and temporal relationships between the strike-slip faults and Mesozoic granitic rocks suggest that these faults acted as the loci for magmatic activity at that time. The deformed fold axes, together with the structural framework of the HJSFS itself, indicate a clockwise sub-vertical rotation of large-scale blocks restricted by the primary strike-slip faults. A variety of structural evidence suggests that the HJSFS experienced three deformation stages, i.e. transpression, transtension and compression. On the basis of offsets of pre-Late Triassic lithofacies, Mesozoic granites, and the Late Silurian suture zone between the Yangtze and Cathaysia Blocks, the total sinistral displacement of the HJSFS is estimated to be 50-60km. The HJSFS is comparable to the Tan-Lu fault with respect to the fault geometry and evolution history. However, the HJSFS has a different structural style, displacement and earthquake intensities from those of the central segment of the Tan-Lu fault, resulting from the differences in crustal structures of the North China Block and South China Block.

红土型风化壳和次生锰矿床形成于温暖和潮湿的古气候条件，其中含有丰富的表生钾锰矿物。因此，对表生钾锰矿物进行精确的40Ar/39Ar年龄测定，不仅能查明大陆化学风化和矿床次生富集的时间和过程，而且可以为区域古气候的反演提供重要的年代学资料。透射电子显微镜、热重分析、离子交换实验和40Ar/39Ar同位素分析表明，层状结构的黑锌锰矿、锂锰矿和钠水锰矿以及具有1×1隧道结构的软锰矿不适合于40Ar/39Ar年龄测定；而隐钾锰矿、锰钡矿和锰铅矿因具有致密和稳定的2×2隧道结构及很强的保存K2Ar体系的能力，是40Ar/39Ar同位素定年的理想对象。硬锰矿和钙锰矿分别具有2×3和3×3隧道结构，由于隧道孔径过大，晶体结构的稳定性较差，其作为40Ar/39Ar测年的适用性有待于进一步证实。采用精细的激光阶段加热技术，可以有效克服表生钾锰矿物40Ar/39Ar测年过程中39ArK的反冲损失、多世代表生钾锰矿物的共生，以及表生钾锰矿物中原生矿物的污染和过量大气氩的存在等问题，并获得有意义的风化年龄。已有数据表明,表生钾锰矿物的形成主要集中在白垩纪末期、始新世末期—渐新世早期、中新世和上新世中期等4个时期，可能记录了地史时期周期性的化学风化及气候的交替演变。

The Jiaodong gold province is the largest gold repository in China. Both mineralization and granitoid hosts are spatially related to the crustal-scale Tan-Lu strike-slip fault system, which developed along the Mesozoic continental margin in eastern China. A series of 40Ar/39Ar laser incremental heating analyses of hydrothermal sericite/muscovite from three major gold deposits (Jiaojia, Xincheng, and Wangershan) and igneous biotite from the granodiorite hosts were performed to establish a possible temporal link between gold mineralization, magmatism, and movement along the Tan-Lu fault zone. Magmatic biotite crystals yield well-defined and concordant plateau ages between 124.5 0.4Ma and 124.± 0.4Ma (2σ), whereas sericite and muscovite samples (a total of 30 single separates) give reproducible plateau ages ranging from 121.± 0.4Ma to 119.2±0.2Ma (2σ). An integration of our 40Ar/39Ar results with age data from other major gold deposits in Jiaodong demonstrates that widespread gold mineralization occurred contemporaneously during a 2-3-m.yr. period. Most gold deposits show intimate spatial associations with abundant mafic to intermediate dikes. The mafic dikes have K-Ar ages of 123.5-119.6Ma, in excellent agreement with those of the gold deposits. These newly obtained 40Ar/39Ar ages, in combination with other independent geological and geochronological data on granodioritic intrusions (130-126Ma), volcanic rocks (1243.6-114.7Ma), and deformed rocks within strike-slip faults (132-120Ma) in Jiaodong or adjacent areas, also support the idea that gold mineralization postdated the granodioritic magmatism but was contemporaneous with mafic magmatism and volcanism, all controlled by the transtensional motion along the Tan-Lu fault in the Early Cretaceous.

Two alkaline syenite plutons, the Tieshan and Yangfang plutons, have recently been recognized within NE-trending fault zones in eastern Cathaysia, South China. The rocks are very enriched in K2O (6.28-9.39wt.%), rare earth elements (REE; particularly light REE) and large ion lithophile elements, but are relatively low in high field strength elements. Isotopically, they are characterized by high initial 87Sr/86Sr (0.7093 to 0.7123) and low eNd(t) values (5.64 to 10.63). The geochemical data suggest that the alkaline syenites most likely formed via fractional crystallization of enriched mantle-derived magmas. Sensitive High-Resolution Ion Microprobe zircon U-Pb dating indicates that these two intrusions have Late Permian (254F4Ma) and Early Triassic (242F4Ma) crystallization ages, respectively. Our data suggest that a tectonic regime dominated by transtension probably existed from at least the latest Permian into the Triassic and was responsible for the formation of the Tieshan and Yangfang alkaline syenites. When combined with previous paleomagnetic, structural, and sedimentology data, we suggest that the transtension along the NE-trending strike-slip fault zones was related to oblique subduction of the Pacific plate underneath South China.

One hundred and twenty-five mineral grains from 45 visually pure K-bearing Mn oxide (hollandite group) samples collected from weathering profiles in the Mt Tabor region of central Queensland, Australia, were analysed by the 40Ar/39Ar laser probe technique. These K-Mn oxides precipitated mainly through a process of cavity filling (direct precipitation from weathering solution), with botryoidal texture formed by micrometric mineral bands. Well-defined and reproducible plateau ages have been obtained for most samples, ranging from 27.2

采用40Ar/39Ar激光阶段加热分析技术，对采自澳大利亚昆士兰中部某风化剖面中的钡硬锰矿和隐钾锰矿进行同位素年龄测定，获得可靠的坪年龄和等时线年龄，再次证明可以用40Ar/39Ar测年技术对极细小的表生锰氧化物进行年代学研究。发现Ar同位素在钡硬锰矿和隐钾锰矿中主要赋存于两种不同的位置。第1种位置（晶间空隙）主要赋存大气成因Ar，在激光功率为0.2～0.4W时释放出来，包括40Aratm, 38Aratmt和Aratm.第2种位置（即隧道结构或晶内位置）主要赋存放射性成因Ar（40Ar*）和核反应成因Ar (39Ark,38Ark)，其去气的激光功率主要在0.5～1.0W之间。当激光功率大于1.0W时，已很少有Ar气从锰氧化物中释放出来，说明赋存放射性成因和核反应成因Ar的隧道结构因持续受热而崩塌、解体。40Ar*,39Ark和38Ark的近于完全一致的去气行为意味着它们不仅在锰氧化物中占有相同或相当的晶体位置，同时证明39Ark在样品接受同位素分析之前的中子照射及实验室预热过程中没有反冲出矿物晶体结构。结果表明，尽管表生锰氧化物中含有大理的大气Ar,且这些氧化物的晶体十分细小，但应用40Ar/39Ar激光阶段加热分析技术可以获得有意义的风化年代学信息。