Nope. You are mixing the semantic value of a blockquote with its (default) presentation.
The purpose of a blockquote is to insert a long quotation (not inline with the main text).
If you just want margins around a piece of text, define a div o p class, with suitable margins.
EDIT: see, for example,
http://www.w3.org/TR/html401/struct/text.html#h-9.2.2 where later you can read:
Quote:
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The usage of BLOCKQUOTE to indent text is deprecated in favor of style sheets.
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or
http://www.w3.org/TR/html5/the-block...kquote-element.