English Locative-Subject Clause: Its Formation Mechanism and Intrinsic Semantic Feature of Theme

English locative-subject clause（ES_LC）refers to clauses whose subject has the LOCATIVE role of designating the place of the state or action.In transitivity structure，ES_LCmay be either relational clauses of circumstance or mental clauses，both of which are clauses of ideational grammatical metaphor.The formation mechanism of the former type involves process transfer，transfer of element function and transfer of element structure.In addition to these three kinds of transfer，the formation of the latter also involves personification.Of the transfers of the formation mechanism，process transfer is determinant.It determines the process type of the transferred clause and the transfer of element function，which in turn decides the transfer of element structure.And personification depends on whether the transferred clause is a mental relation clause or not.In thematic structure，the subject of ES_LC may be regarded as unmarked Theme，which is different in nature from that of its corresponding congruent clause.The unmarked Theme of ES_LC may be the point of departure of the message，but，due to its own intrinsic semantic feature of location，it cannot be what the Rheme is about，but provides a spatial location for the state or action of the Rheme.