Provenance of Lower Carboniferous Bauxite Deposits in Northern Guizhou,China:Constraints from Geochemistry and Detrital Zircon U-Pb Ages

The Lower Carboniferous Jiujialu Formation bauxite deposits of northern Guizhou Province,China,are a Kazakhstan subtype of karst bauxite deposits.The provenance of the Jiujialu Formation has long been debated,with uncertainty about the formation of the bauxite deposits.Here we report new geochemical data that indicate the affinity between the Lower-Middle Ordovician clastic rocks and argillaceous dolostones and the overlying Carboniferous bauxite deposits,all of which are characterized by high Al_(2)0_(3),K2_(O),and∑REE contents,flat post-Archean Australian shale(PAAS)-normalized REE patterns,and uniform immobile element ratios(TiO2/Al_(2)0_(3),Nb/TiO2,and Zr/TiO2).Their similar detrital zircon age distributions further indicate the link between the bauxite deposits and the clastic rocks and argillaceous dolostones.Zircon age spectra of clastic rocks of the Lower Silurian Hanchiatien Formation in northern Guizhou match those of the bauxite deposits,with a maximum age peak at-980 Ma and other secondary age peaks,suggesting these clastic rocks may represent the provenance of the bauxite deposits.The youngest detrital zircons(-445 Ma)occur only in the bauxite deposits and are probably sourced from K-bentonite beds of the Ordovician-Silurian tran-sition.Our analyses indicate that the source materials of the bauxite deposits in the Jiujialu Formation are of mixed provenance:Lower-Middle Ordovician aluminosilicate rocks and argillaceous dolostones of the underlying strata,and Lower Silurian clastic rocks and K-bentonite from adjacent areas.A comparison of Early Carboniferous bauxitic provenances in northern and central Guizhou indicates that paleotopography was the major factor controlling the provenance of these bauxite deposits.

A modelling method for large-scale open spaces orientated toward coordinated control of multiple air-terminal units

The temperature distribution is always assumed to be homogeneous in a traditional singleinput-single-output(SISO)air conditioning control strategy.However,the airflow inside is more complicated and unpredictable.This study proposes a zonal temperature control strategy with a thermal coupling effect integrated for air-conditioned large-scale open spaces.The target space was split into several subzones based on the minimum controllable air terminal units in the proposed method,and each zone can be controlled to its own set-point while considering the thermal coupling effect from its adjacent zones.A numerical method resorting to computational fluid dynamics was presented to obtain the heat transfer coefficients(HTCs)under different air supply scenarios.The relationship between heat transfer coefficient and zonal temperature difference was linearized.Thus,currently available zonal models in popular software can be used to simulate the dynamic response of temperatures in large-scale indoor open spaces.Case studies showed that the introduction of HTCs across the adjacent zones was capable of enhancing the precision of temperature control of large-scale open spaces.It could satisfy the temperature requirements of different zones,improve thermal comfort and at least 11%of energy saving can be achieved by comparing with the conventional control strategy.