Abstract About 200 known coastal deposits of heavy mineral sands (HMS) occur in China, in which considerable mineral resources of titanium, zircon, rare earth elements, and thorium exist in the forms of ilmenite, rutile, zircon, and monazite. More than 20 of these HMS deposits are reported as having been or are actively being mined in China during the past three decades, of which 12 have been reported to have industrial resources. Commercially important deposits occur almost entirely in Cenozoic beach and sand dune deposits, principally along China’s eastern coast (e.g., Shandong Province) and southern coast (e.g., Guangxi, Guangdong, Hainan, and Fujian provinces), and particularly on Hainan island. There are also important deposits of HMS along coastal areas of Taiwan. China has the largest share of the world’s economic ilmenite resources in HMS deposits (31%). A variety of igneous and associated metamorphic rocks along the coastal areas of China provided an abundant source of heavy minerals for the formation of the HMS occurrences. Studies of titanium-rich HMS deposits have shown that ilmenite is mostly sourced from igneous rocks. For example, 40% of the bedrock of Hainan island consists of Triassic and Cretaceous granites emplaced into rocks of the Cathyasia Block, and all of the HMS districts on the island lie no more than 15 km downstream from a Middle Triassic suite of syenite to granite intrusions. The southern coastal regions of Guangdong and Guangxi provinces are dominated by Jurassic granodiorite, biotite granite, two-mica granite, and A-type granite, with minor gabbro and syenite. Identified accessory minerals in the Jurassic alkaline granitoids include zircon, apatite, allanite, titanite, magnetite, ilmenite, monazite, and niobite. Thus, multiple plutons are in proximity to the Cenozoic coastal plain and are available as bedrock sources for the detrital titanium minerals, zircon, and monazite. More than 100 HMS deposits and prospects have been identified in Shandong Province, consisting of more than 20 varieties of heavy minerals in quartz sand, which include zircon, ilmenite, rutile, monazite, magnetite, xenotime, and gold (in general order of abundance) derived from Precambrian metamorphic basement and Mesozoic intrusions. Of these minerals, zircon, magnetite, gold, and quartz sand have economic significance. The quartz sands are used by the glass and construction industries. The placers mainly occur in and adjacent to the littoral zones of the northern and southern coasts of the Jiaodong Peninsula in Shandong province. Seven beach placer, HMS prospective areas have been delineated in coastal areas of the peninsula. Due to nearly exhausted placer reserves in the Chinese coastal zones, as well as increased environmental restrictions, future prospecting for heavy minerals will likely focus on ancient beach systems in China’s inland sedimentary basins. Also, offshore deposits of HMS in shallow coastal waters are other potential sources of heavy minerals, such as the Baoding Sea zircon-titanium, minerals-rich placer under development near Wanning on Hainan. Similarly, there is potential for offshore HMS deposits in shallow waters of the entire coastal area of southern Taiwan that remains to be fully evaluated. Reconnaissance sampling along Taiwan island’s coasts has revealed the potential for extensive, high-grade HMS accumulations nearshore.
AbstractSedimentary uranium mineralisation in South Australia is mostly in Cainozoic basinal palaeochannels developed on or proximal to Precambrian cratons. Precambrian basement of the Gawler and Curnamona cratons have uranium contents in the range 10-100 ppm, well above the crustal average of 2.8 ppm U. Deeply weathered basement rocks in these regions were incised during early Tertiary times and the sediments in these palaeodrainage networks now form several significant uranium provinces. The palaeochannel uranium deposits are typically hosted by medium to coarse-grained sandstone deposited in a continental fluvial, latchstring, alluvial, or marginal marine sedimentary environment. Impermeable clay units are intercalated in the sedimentary sequence and often occur immediately above and below the mineralised sandstone. Uranium mineralisation is associated with reduced conditions, and similar to elsewhere in the world, the host sediments to the Tertiary uranium mineralisation often contain pyrite and organic (plant) matter that is either disseminated or forms lignite seams. Tabular or roll-front shaped mineralised bodies formed along the contact with clay horizons and also along the palaeochannel margins. Tertiary continental sediments in SA are important favourable hosts because of the high organic content in channel sediments due to widespread colonisation by land plants during this time.The precise geometric definition of a palaeochannel is important in the selection of exploration targets for sandstone uranium. This often requires the integration of various geoscientific data sets in order to define targets and to improve the effectiveness of drilling. Refinements in remote sensing and geophysical techniques, data processing, sedimentology and computer-aided interpretations provide an effective, economic and efficient method of outlining the principal drainage patterns and channel dimensions. An improved understanding of sedimentary models and their relationship to uranium distribution will assist the effectiveness of exploration industry to explore for uranium in buried channel systems.Keywordspalaeochanneluranium.
Abstract The Eocene succession filling palaeovalleys in the northeastern Eucla Basin, South Australia, is interpreted using facies and sequence-stratigraphic models based on relative sea-level changes. The dominantly fluvial sediments were deposited in incised valleys which graded basinwards to an estuarine coastal plain under warm and humid palaeoclimatic conditions. Sedimentological examination suggests a tidal influence in this fluvial succession. Fluvial–estuarine-shoreline facies associations can be recognised in these (Eocene) sequences, each of which comprises a diverse assemblage of lithofacies that can be grouped into lowstand and/or transgressive and highstand system tracts. Since the palaeorivers had hydrological connection with the sea, deposition was dominantly controlled by sea-level changes. Results of the study indicate that two third-order Eocene eustatic cycles have largely controlled sedimentation. The resulting key surfaces (unconformity, and transgressive, tidal/wave ravinement, and maximum flooding surfaces) bound depositional sequences which extend over significant areas and may be used in basin-wide correlations of stratal packages.
The Chinese method is a variation of the original CHIM (CHastichnoe Izvlechennye Metallov) technique developed by Russian scientists in the early 1970s (Ryss et al. 1977). In the 1980s this method spread to China and India where it was widely applied. In the early 1990s, with an increased knowledge of weathering halos around ore bodies and the increased necessity to detect deeply buried ore deposit, interest spread to western countries such as the USA and Canada.
'/%3e%3c/defs%3e%3cpath fill='%23012169' d='M0 0h10080v5040H0z'/%3e%3cpath stroke='%23fff' stroke-width='.6' d='m0 0 6 3m0-3L0 3' clip-path='url(%23b)' transform='scale(840)'/%3e%3cpath stroke='%23e4002b' stroke-width='.4' d='m0 0 6 3m0-3L0 3' clip-path='url(%23c)' transform='scale(840)'/%3e%3cpath stroke='%23fff' stroke-width='840' d='M2520 0v2520M0 1260h5040'/%3e%3cpath stroke='%23e4002b' stroke-width='504' d='M2520 0v2520M0 1260h5040'/%3e%3cg fill='%23fff'%3e%3cuse xlink:href='%23d' x='2520' y='3780'/%3e%3cuse xlink:href='%23a' x='7560' y='4200'/%3e%3cuse xlink:href='%23a' x='6300' y='2205'/%3e%3cuse xlink:href='%23a' x='7560' y='840'/%3e%3cuse xlink:href='%23a' x='8680' y='1869'/%3e%3cuse xlink:href='%23e' x='8064' y='2730'/%3e%3c/g%3e%3c/svg%3e)
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)